JEE Main 10 April 2023 Shift 2 question paper with solutions
JEE Main 10 April 2023 Shift 2: all 90 questions in paper order (Maths, Physics, Chemistry) with the answer key and worked solutions. Free to read; attempt it as a timed 3-hour mock test.
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Maths
Question 1
Maths · Integrals · Single correct
Let $f$ be a continuous function satisfying $\displaystyle\int_0^{t^2} \left(f(x) + x^2\right)dx = \frac{4}{3}t^3, \quad \forall t > 0$. Then $f\left(\dfrac{\pi^2}{4}\right)$ is equal to
$\pi^2\left(1 - \dfrac{\pi^2}{16}\right)$
$-\pi\left(1 + \dfrac{\pi^3}{16}\right)$
$\pi\left(1 - \dfrac{\pi^3}{16}\right)$
$-\pi^2\left(1 + \dfrac{\pi^2}{16}\right)$
Answer: (c)
Solution
Given equation is $\int_0^{t^2} \left( f(x) + x^2 \right) dx = \frac{4}{3} t, \forall t > 0$. According to Newton Leibnitz theorem we have $$\frac{d}{dx} \left( \int_{u(x)}^{v(x)} f(t) dt \right) = f(v(x)) \times v'(x) - f(u(x)) \times u'(x).$$ Apply Newton's Leibnitz theorem in the given equation. $$\Rightarrow \left( f(t^2) + t^4 \right) 2t - 0 = 4t^2$$ $$\Rightarrow f(t^2) + t^4 = 2t$$ $$\Rightarrow f(x^2) = -x^4 + 2x$$ $$\Rightarrow f(x) = -x^2 + 2 \sqrt{x}$$ $$\Rightarrow f\left( \frac{\pi^2}{4} \right) = -\frac{\pi^4}{4} + 2 \times \frac{\pi}{2}$$ $$= -\frac{\pi^4}{16} + \pi$$ $$= \pi \left( 1 - \frac{\pi^3}{16} \right)$$ Hence this is the correct option.
Question 2
Maths · Permutations and Combinations · Single correct
Eight persons are to be transported from city A to city B in three cars of different makes. If each car can accommodate at most three persons, then the number of ways, in which they can be transported, is
1120
3360
1680
560
Answer: (c)
Solution
Let us find the different ways so that 8 persons can travel in 3 cars. $$\begin{array}{|c|c|c|} \hline C_1 & C_2 & C_3 \\ \hline 3 & 3 & 2 \\ 2 & 3 & 3 \\ 3 & 2 & 3 \\ \hline \end{array}$$ Hence we have 3 ways. Now the number of ways to distribute 8 persons such that they can travel in 3 cars with any car carrying maximum of 3 persons is $$\left( \frac{8!}{3!3!2!} \right) \times 3 = 1680$$ Therefore, the required answer is 1680.
Question 3
Maths · Integrals · Single correct
For $\alpha, \beta, \gamma, \delta \in \mathbb{N}$, if $$\int \left( \left( \frac{x}{e} \right)^{2x} + \left( \frac{e}{x} \right)^{2x} \right) \log_e x \, dx = \frac{1}{\alpha} \left( \frac{x}{e} \right)^{\beta x} - \frac{1}{\gamma} \left( \frac{e}{x} \right)^{\delta x} + C,$$ where $e = \sum_{n=0}^{\infty} \frac{1}{n!}$ and $C$ is constant of integration, then $\alpha + 2\beta + 3\gamma - 4\delta$ is equal to
1
4
-4
-8
Answer: (b)
Solution
Given, $$\int \left( \left( \frac{x}{e} \right)^{2x} + \left( \frac{e}{x} \right)^{2x} \right) \ln x \, dx = \frac{1}{\alpha} \left( \frac{x}{e} \right)^{\beta x} - \frac{1}{\gamma} \left( \frac{e}{x} \right)^{\delta x} + C$$ Now let $$I = \int \left( \left( \frac{x}{e} \right)^{2x} + \left( \frac{e}{x} \right)^{2x} \right) \ln x \, dx$$ Now let $$\left( \frac{x}{e} \right)^{2x} = t$$ $$\Rightarrow 2x(\ln x - 1) = \ln t$$ $$\Rightarrow \ln x \, dx = \frac{1}{2t} \, dt$$ So, $$I = \frac{1}{2} \int \left( t + \frac{1}{t} \right) \frac{dt}{t}$$ $$\Rightarrow I = \frac{1}{2} \int \left( 1 + \frac{1}{t^2} \right) dt$$ $$\Rightarrow I = \frac{1}{2} \left( t - \frac{1}{t} \right) + C$$ $$\Rightarrow I = \frac{1}{2} \left( \left( \frac{x}{e} \right)^{2x} - \left( \frac{e}{x} \right)^{2x} \right) + C$$ Now on comparing with $$I = \frac{1}{\alpha} \left( \frac{x}{e} \right)^{\beta x} - \frac{1}{\gamma} \left( \frac{e}{x} \right)^{\delta x} + C$$, we get $$\alpha = 2, \beta = 2, \gamma = 2, \delta = 2$$ Hence, $$\alpha + 2\beta + 3\gamma - 4\delta = 2 + 4 + 6 - 8 = 4$$ Hence this is the required option.
Question 4
Maths · Three Dimensional Geometry · Single correct
Let the image of the point P(1, 2, 6) in the plane passing through the points A(1, 2, 0) and B(1, 4, 1) C(0, 5, 1) be Q($\alpha$, $\beta$, $\gamma$) . Then ($\alpha^2$ + $\beta^2$ + $\gamma^2$) equal to
65
62
76
70
Answer: (a)
Solution
Plane passes through the points A(1, 2, 0), B(1, 4, 1) and C(0, 5, 1). We know that the equation of a plane passing through three non-collinear points $(x_1, y_1, z_1), (x_2, y_2, z_2), (x_3, y_3, z_3)$ is $$\begin{vmatrix} x - x_1 & y - y_1 & z - z_1 \\ x_2 - x_1 & y_2 - y_1 & z_2 - z_1 \\ x_3 - x_1 & y_3 - y_1 & z_3 - z_1 \end{vmatrix} = 0$$ $$\begin{vmatrix} x - 1 & y - 2 & z - 0 \\ 1 - 1 & 4 - 2 & 1 - 0 \\ 0 - 1 & 5 - 2 & 1 - 0 \end{vmatrix} = 0$$ $$\begin{vmatrix} x - 1 & y - 2 & z - 0 \\ 0 & 2 & 1 \\ -1 & 3 & 1 \end{vmatrix} = (x - 1)(2 - 3) + (y - 2)(0 + 1) + z(0 + 2) = 0$$ $$-x + 1 - y + 2 + 2z = 0$$ $$x + y - 2z = 3 \ldots (i)$$ Now image of P(1, 2, 6) in (i) $$\frac{x - 1}{1} = \frac{y - 2}{1} = \frac{z - 6}{-2} = \frac{-2(-9 - 3)}{6} = 4$$ $$x = 5, \; y = 6, \; z = -2$$ $$\alpha = 5, \; \beta = 6, \; \gamma = -2$$ $$\therefore \alpha^2 + \beta^2 + \gamma^2 = 65$$ Hence this is the required option.
Question 5
Maths · Relations and Functions · Single correct
Let $A = \{2, 3, 4\}$ and $B = \{8, 9, 12\}$. Then the number of elements in the relation $R = \{((a_1, b_1), (a_2, b_2)) \in (A \times B, A \times B): a_1 divides b_2 and a_2 divides b_1\}$ is
36
24
18
12
Answer: (a)
Solution
Given, $A = \{2, 3, 4\}$, $B = \{8, 9, 12\}$. And $a_1 \in A$, $b_2 \in B$. Now finding elements where $a_1$ divides $b_2$, we get, $$(a_1, b_2) \in \{(2, 8), (2, 12), (3, 9), (3, 12), (4, 8), (4, 12)\}$$ Also given, $a_2 \in A$, $b_1 \in B$. Now finding elements when $a_2$ divides $b_1$, we get, $$(a_2, b_1) \in \{(2, 8), (2, 12), (3, 9), (3, 12), (4, 8), (4, 12)\}$$ Hence, Number of relations $= 6 \times 6 = 36$
Question 6
Maths · Matrices · Single correct
If $A = \frac{1}{5!6!7!} \begin{vmatrix} 5! & 6! & 7! \\ 6! & 7! & 8! \\ 7! & 8! & 9! \end{vmatrix}$, then $|adj(adj(2A))|$ is equal to
$2^{20}$
$2^8$
$2^{12}$
$2^{16}$
Answer: (d)
Solution
Given, $$A = \frac{1}{5!6!7!} \begin{bmatrix} 5! & 6! & 7! \\ 6! & 7! & 8! \\ 7! & 8! & 9! \end{bmatrix}$$ $\($$\Rightarrow$ |A| = $\frac{1}{5!6!7!}$ $\begin{vmatrix}$ 5! & 6! & 7! $\\$ 6! & 7! & 8! $\\$ 7! & 8! & 9! $\end{vmatrix}$$\)$ $\($$\Rightarrow$ |A| = $\frac{1}{5!6!7!}$ $\begin{vmatrix}$ 1 & 6 & 42 $\\$ 1 & 7 & 56 $\\$ 1 & 8 & 72 $\end{vmatrix}$$\)$ $\($$\Rightarrow$ |A| = 2$\)$ Now using the property of adjoint of matrix we get, $$|adj(adj(A))| = |A|^{(n-1)^2} \& |kA| = k^n |A|,$$ where $\($n$\)$ is order of square matrix, Now using the above two formula we get, $$|adj(adj(2A))| = |2A|^{(2-1)^2} |A|^4$$ $\($$\Rightarrow$ |adj(adj(2A))| = $2^{12}$ $\cdot$ $2^4$\)$ $\($$\Rightarrow$ |adj(adj(2A))| = $2^{16}$\)
Question 7
Maths · Straight Lines and Pair of Straight Lines · Single correct
Let A be the point (1, 2) and B be any point on the curve $x^2 + y^2 = 16$. If the centre of the locus of the point P, which divides the line segment AB in the ratio 3 : 2 is the point C($\alpha$, $\beta$), then the length of the line segment AC is
$\frac{3\sqrt{5}}{5}$
$\frac{4\sqrt{5}}{5}$
$\frac{2\sqrt{5}}{5}$
$\frac{6\sqrt{5}}{5}$
Answer: (a)
Solution
Given, let $A$ be the point $(1, 2)$ and $B$ be any point on the curve $x^2 + y^2 = 16$. And the centre of the locus of the point $P$, which divides the line segment $AB$ in the ratio $3 : 2$ is the point $C(\alpha, \beta)$. Now let the point on the circle $x^2 + y^2 = 16$ be $B(4 \cos \theta, 4 \sin \theta)$. Now using section formula in $A(1, 2)$ and $B(4 \cos \theta, 4 \sin \theta)$ we get, $$P \left( \frac{12 \cos \theta + 2}{5}, \frac{12 \sin \theta + 4}{5} \right) \equiv (h, k)$$ $$\Rightarrow \cos \theta = \frac{5h - 2}{12} \& \sin \theta = \frac{5k - 4}{12}$$ Now squaring and adding we get, $$\left( \frac{5h - 2}{12} \right)^2 + \left( \frac{5k - 4}{12} \right)^2 = 1$$ $$\Rightarrow \left( h - \frac{2}{5} \right)^2 + \left( k - \frac{4}{5} \right)^2 = \left( \frac{12}{5} \right)^2$$ So, the centre of the locus is $C \left( \frac{2}{5}, \frac{4}{5} \right)$. Hence, by distance formula we get, $$AC = \sqrt{ \left( \frac{3}{5} \right)^2 + \left( \frac{6}{5} \right)^2 } = \frac{3 \sqrt{5}}{5}$$
Question 8
Maths · Probability · Single correct
Let a die be rolled n times. Let the probability of getting odd numbers seven times be equal to the probability of getting odd numbers nine times. If the probability of getting even numbers twice is $\frac{k}{2^{15}}$, then $k$ is equal to
60
15
90
30
Answer: (a)
Solution
Given that $P(getting odd 7 times) = P(getting odd 9 times)$. This is the case of binomial distribution with $n$ successes and probability of success $= p = \frac{3}{6}$ and failure is $q = 1 - p = \frac{1}{2}$. We know that $P(X = k) = \binom{n}{k} (p)^k (q)^{n-k}$. Now $P(X = 7) = P(X = 9)$ $$\Rightarrow \binom{n}{7} \left( \frac{1}{2} \right)^7 \left( \frac{1}{2} \right)^{n-7} = \binom{n}{9} \left( \frac{1}{2} \right)^9 \left( \frac{1}{2} \right)^{n-9}$$ $$\Rightarrow \binom{n}{7} = \binom{n}{9}$$ $$\Rightarrow \binom{n}{n-7} = \binom{n}{9}$$ $$\Rightarrow n = 16$$ $$\Rightarrow P\left(2 times even\right) = \binom{16}{2} \left( \frac{1}{2} \right)^{14} \left( \frac{1}{2} \right)^2$$ $$= \frac{15 \times 4}{2^{15}} = \frac{60}{2^{15}} = \frac{k}{2^{15}}$$ $$\Rightarrow k = 60$$ Hence this is the required option.
Question 9
Maths · Applications of Derivatives · Single correct
Let $g(x) = f(x) + f(1-x)$ and $f''(x) > 0$, $x \in (0, 1)$. If $g$ is decreasing in the interval $(0, \alpha)$ and increasing in the interval $(\alpha, 1)$, then $\tan^{-1} 2\alpha + \tan^{-1} \left( \frac{1}{\alpha} \right) + \tan^{-1} \left( \frac{\alpha + 1}{\alpha} \right)$ is equal to
$\pi$
$\frac{5\pi}{4}$
$\frac{3\pi}{4}$
$\frac{3\pi}{2}$
Answer: (a)
Solution
Given, $g(x) = f(x) + f(1-x)$ and $f''(x) > 0$, $x \in (0, 1)$. If $g$ is decreasing in the interval $(0, \alpha)$ and increasing in the interval $(\alpha, 1)$, Now solving, $$g(x) = f(x) + f(1-x)$$ Now differentiating both sides we get, $$g'(x) = f'(x) - f'(1-x)$$ Differentiating again we get, $$g''(x) = f''(x) + f''(1-x) > 0$$ So, $g'(x)$ is increasing as given $f''(x) > 0$ $$\Rightarrow g'(0) < g'(1)$$ $$\Rightarrow f'(0) - f'(1) < f'(1) - f'(0)$$ $$\Rightarrow f'(0) < f'(1)$$ Now finding $g'(x) = 0$ we get, $$\Rightarrow f'(x) = f'(1-x)$$ $$\Rightarrow x = 1 - x$$ $$\Rightarrow x = \frac{1}{2}$$ Now $g'(x)$ is positive for $x \in \left(0, \frac{1}{2}\right)$ And $g'(x)$ is negative for $x \in \left(\frac{1}{2}, 1\right)$ $$\therefore \alpha = \frac{1}{2}$$ So, $$\tan^{-1} 2\alpha + \tan^{-1} \left(\frac{1}{\alpha}\right) + \tan^{-1} \left(\frac{\alpha + 1}{\alpha}\right)$$ $$= \tan^{-1} 1 + \tan^{-1} 2 + \tan^{-1} 3$$ $$= \frac{\pi}{4} + \tan^{-1} \left(\frac{2 + 3}{1 - 6}\right)$$ $$= \frac{\pi}{4} + \tan^{-1} (-1)$$ $$= \frac{\pi}{4} + \frac{3\pi}{4} = \pi$$
Question 10
Maths · Conic Sections · Single correct
Let a circle of radius 4 be concentric to the ellipse $15x^2 + 19y^2 = 285$. Then the common tangents are inclined to the minor axis of the ellipse at the angle
$\frac{\pi}{3}$
$\frac{\pi}{4}$
$\frac{\pi}{6}$
$\frac{\pi}{12}$
Answer: (a)
Solution
Given, $$15x^2 + 19y^2 = 285$$ $\($$\Rightarrow$ $\frac{x^2}{19}$ + $\frac{y^2}{15}$ = 1$\)$ Now plotting the diagram with given circle of radius 4 we get, $$\frac{x^2}{19} + \frac{y^2}{15} = 1$$ Now, let the equation of tangent of ellipse be $\($y = mx $\pm$ $\sqrt{19m^2 + 15}$$\)$ $\{$as $\($c^2 = a^2m^2 + b^2$\)$$\}$ If it is tangent to circle $\($x^2 + y^2 = 16$\)$ then using the formula, $\($c^2 = r^2(1 + m^2)$\)$ we get, $$\frac{\sqrt{19m^2 + 15}}{\sqrt{1 + m^2}} = 4$$ $\($$\Rightarrow$ 19m^2 + 15 = 16 + 16m^2$\)$ $\($$\Rightarrow$ 3m^2 = 1$\)$ $\($$\Rightarrow$ m = $\pm$ $\frac{1}{\sqrt{3}}$$\)$ $\($$\Rightarrow$ $\theta$ = 30^$\circ$$\)$ with $\($x-axis$\)$, Hence, Angle made by tangent with minor axis i.e., with $\($y-axis$\)$ is $\($$\frac{\pi}{3}$$\)$
Question 11
Maths · Vector Algebra · Single correct
Let $\vec{a} = 2\hat{i} + 7\hat{j} - \hat{k}$, $\vec{b} = 3\hat{i} + 5\hat{k}$ and $\vec{c} = \hat{i} - \hat{j} + 2\hat{k}$. Let $\vec{d}$ be a vector which is perpendicular to both $\vec{a}$ and $\vec{b}$, and $\vec{c} \cdot \vec{d} = 12$. Then $\left( -\hat{i} + \hat{j} - \hat{k} \right) \cdot \left( \vec{c} \times \vec{d} \right)$ is equal to
If $S_n = 4 + 11 + 21 + 34 + 50 + \ldots$ to $n$ terms, then $\frac{1}{60}(S_{29} - S_9)$ is equal to
223
226
220
227
Answer: (a)
Solution
Given, $S_n=4+11+21+34+\cdots+T_n$ $S_n=4+11+21+34+\cdots+T_{n-1}+T_n$ Subtracting above equations, we get $0=4+7+10+13+\cdots-T_n$ $\Rightarrow\ T_n=4+7+10+13+\cdots$ The above series is in AP. $\Rightarrow\ T_n=\frac{n}{2}\left(2\times4+(n-1)3\right)$ $\Rightarrow\ T_n=\frac{n}{2}(3n+5)$ So, $S_n=\sum_{n=1}^{n}\frac{3n^2+5n}{2}$ $\Rightarrow\ S_n=\frac{1}{2}\left(\frac{3n(n+1)(2n+1)}{6}+\frac{5n(n+1)}{2}\right)$ $\Rightarrow\ S_n=\frac{n(n+1)}{2}\left(\frac{2n+1}{2}+\frac{5}{2}\right)$ $\Rightarrow\ S_{29}=\frac{29\times30}{2}\left(\frac{59}{2}+\frac{5}{2}\right)$ $\Rightarrow\ S_{29}=29\times15\times32=13920$ $\Rightarrow\ S_{9}=\frac{9\times10}{2}\left(\frac{19}{2}+\frac{5}{2}\right)$ $\Rightarrow\ S_{9}=9\times5\times12=540$ $\Rightarrow\ \frac{S_{29}-S_{9}}{60}=\frac{13920-540}{60}=223$ Therefore, the required answer is $223$.
Question 13
Maths · Properties of Triangles · Single correct
If the points $P$ and $Q$ are respectively the circumcenter and the orthocentre of a $\triangle ABC$, then $\overrightarrow{PA} + \overrightarrow{PB} + \overrightarrow{PC}$ is equal to
$\overrightarrow{2QP}$
$\overrightarrow{2PQ}$
$\overrightarrow{PQ}$
$\overrightarrow{QP}$
Answer: (c)
Solution
Let $P$ be origin. Now from the above triangle we can write $\overrightarrow{PA} = \overrightarrow{a}$, $\overrightarrow{PB} = \overrightarrow{b}$, $\overrightarrow{PC} = \overrightarrow{c}$. Also, we know that centroid $G$ divides orthocentre $Q$ and circumcentre $P$ in the ratio $2 : 1$. $$\overrightarrow{PG} = \frac{\overrightarrow{a} + \overrightarrow{b} + \overrightarrow{c}}{3}$$ Now $\overrightarrow{PQ} = 3 \left( \frac{\overrightarrow{a} + \overrightarrow{b} + \overrightarrow{c}}{3} \right)$ $$\Rightarrow \overrightarrow{PQ} = \overrightarrow{a} + \overrightarrow{b} + \overrightarrow{c} = \overrightarrow{PA} + \overrightarrow{PB} + \overrightarrow{PC}$$ Therefore, the required answer is $PQ$.
Question 14
Maths · Mathematical Reasoning · Single correct
The statement $\sim [p \lor (\sim (p \land q))]$ is equivalent to
$\sim (p \land q)$
$(p \land q) \land (\sim p)$
$(\sim (p \land q)) \land q$
$\sim (p \lor q)$
Answer: (b)
Solution
Given, $\sim [p \lor (\sim (p \land q))]$ Now we know that, By demorgan law, $\sim (A \lor B) \equiv \sim A \land \sim B$ Now using above formula we get, $\sim [p \lor (\sim (p \land q))]$ $\equiv \sim p \land (p \land q)$ [as $\sim (\sim A) \equiv A$] $\equiv (p \land q) \land (\sim p)$
Question 15
Maths · Trigonometric Functions · Single correct
Let $\mathcal{S} = \left\{ x \in \left( -\frac{\pi}{2}, \frac{\pi}{2} \right) : 9^{1 - \tan^2 x} + 9^{\tan^2 x} = 10 \right\}$ and $\beta = \sum_{x \in \mathcal{S}} \tan^2 \left( \frac{x}{3} \right)$, then $\frac{1}{6} \left( \beta - 14 \right)^2$ is equal to
16
8
64
32
Answer: (d)
Solution
Given, $9^{1 - \tan^2 x} + 9^{\tan^2 x} = 10$. Now let $9^{\tan^2 x} = t$, then the above equation will be, $$\frac{9}{t} + t = 10$$ $$\Rightarrow t^2 - 10t + 9 = 0$$ $$\Rightarrow t = 9 or t = 1$$ So, when $9^{\tan^2 x} = 9 \Rightarrow \tan^2 x = 1$ $$\Rightarrow \tan x = \pm 1 \Rightarrow x = \pm \frac{\pi}{4}, as given x \in \left( -\frac{\pi}{2}, \frac{\pi}{2} \right)$$ Now when $9^{\tan^2 x} = 1$ $$\Rightarrow \tan^2 x = 0 \Rightarrow x = 0$$ Hence, $$\beta = \sum_{x \in S} \left( \frac{x}{3} \right) = \tan^2 \left( \frac{0}{3} \right) + \tan^2 \left( \frac{\pi}{12} \right) + \tan^2 \left( -\frac{\pi}{12} \right)$$ $$= 0 + 2 \left( 2 - \sqrt{3} \right)^2$$ $$= 14 - 8\sqrt{3}$$ So, the value of $\frac{1}{6} \left( \beta - 14 \right)^2 = \frac{64 \times 3}{32} = 32$. Hence this is the correct option.
Question 16
Maths · Binomial Theorem · Single correct
If the coefficients of $x$ and $x^2$ in $(1+x)^p(1-x)^q$ are 4 and $-5$ respectively, then $2p + 3q$ is equal to
60
69
66
63
Answer: (d)
Solution
Given that the coefficient of $x$ and $x^2$ in $(1 + x)^p (1 - x)^q$ are 4 and $-5$. $$\Rightarrow \left(1 + x\right)^p (1 - x)^q = \left(1 + px + \frac{p(p-1)}{2!} x^2 + \ldots \right) \left(1 - qx + \frac{q(q-1)}{2!} x^2 - \ldots \right)$$ Now coefficient of $x$ from the above expansion will be $p - q$ which is equal to 4 $$\Rightarrow p - q = 4.$$ Similarly coefficient of $x^2$ is $-5$. $$\Rightarrow \frac{p(p-1)}{2} + \frac{q(q-1)}{2} - pq = -5$$ $$\Rightarrow \frac{p^2 - 2pq + q^2}{2} - \frac{(p+q)}{2} = -5$$ $$\Rightarrow \frac{(p-q)^2}{2} - \frac{(p+q)}{2} = -5$$ $$\Rightarrow \frac{16}{2} + 5 = \frac{(p+q)}{2}$$ $$\Rightarrow p + q = 26 and p - q = 4$$ On solving the above equations we get, $$p = 15 and q = 11.$$ $$\Rightarrow 2p + 3q = 2(15) + 3(11) = 63$$ Therefore, the required answer is 63.
Question 17
Maths · Three Dimensional Geometry · Single correct
Let the line $\frac{x}{1} = \frac{6-y}{2} = \frac{z+8}{5}$ intersect the lines $\frac{x-5}{4} = \frac{y-7}{3} = \frac{z+2}{1}$ and $\frac{x+3}{6} = \frac{3-y}{3} = \frac{z-6}{1}$ at the points $A$ and $B$ respectively. Then the distance of the mid-point of the line segment $AB$ from the plane $2x - 2y + z = 14$ is
3
$\frac{11}{3}$
4
$\frac{10}{3}$
Answer: (c)
Solution
Given, the line $\frac{x}{1} = \frac{6-y}{2} = \frac{z+8}{5}$ intersect the lines $\frac{x-5}{4} = \frac{y-7}{3} = \frac{z+2}{1}$ and $\frac{x+3}{6} = \frac{3-y}{3} = \frac{z-6}{1}$ at the points $A$ and $B$ respectively. Now plotting the diagram, we get, $$\frac{x}{1} = \frac{y-6}{-2} = \frac{z+8}{5}$$ $$\frac{x-5}{4} = \frac{y-7}{3} = \frac{z+2}{1}$$ $$\frac{x+3}{6} = \frac{y-3}{-3} = \frac{z-6}{1}$$ Now solving, $\frac{x}{1} = \frac{y-6}{-2} = \frac{z+8}{5} = \lambda$ and $\frac{x-5}{4} = \frac{y-7}{3} = \frac{z+2}{1} = t$ we get, $$A \equiv (\lambda, -2\lambda + 6, 5\lambda - 8) \equiv (4t + 5, 3t + 7, t - 2)$$ Now comparing both side and solving we get, $t = -1, \lambda = 1$. Hence, point $A(1, 4, -3)$. Now solving, $\frac{x}{1} = \frac{y-6}{-2} = \frac{z+8}{5} = \mu$ and $\frac{x+3}{6} = \frac{y-3}{-3} = \frac{z-6}{1} = k$ we get, $$B \equiv (\mu, -2\mu + 6, 5\mu - 8) \equiv (6k - 3, -3k + 3, k + 6)$$ Now comparing both side and solving we get, $k = 1, \mu = 3$. Hence, point $B(3, 0, 7)$. So, mid-point of $AB = M(2, 2, 2)$. Now finding, distance of $M$ from the plane $2x - 2y + z - 14 = 0$ we get, $$\left| \frac{4 - 4 + 2 - 14}{\sqrt{2^2 + 2^2 + 1^2}} \right| = \left| \frac{-12}{3} \right| = 4$$
Question 18
Maths · Complex Numbers and Quadratic Equations · Single correct
Let $S = \left\{ z = x + iy : \frac{2x - 3i}{4x + 2i} \text{ is a real number} \right\}$. Then which of the following is NOT correct?
Let the number $(22)^{2022} + (2022)^{22}$ leave the remainder $\alpha$ when divided by 3 and $\beta$ when divided by 7. Then $(\alpha^2 + \beta^2)$ is equal to
20
13
5
10
Answer: (c)
Solution
Given that $\alpha$ be the remainder when $(22)^{2022} + (2022)^{22}$ is divided by 3 and $\beta$ be the remainder when the same is divided by 7. $$\Rightarrow (22)^{2022} + (2022)^{22} = (21 + 1)^{2022} + (2022)^{22}.$$ Here $(2022)^{22}$ is divisible by 3 as 2022 is divisible by 3. So on expanding $(21 + 1)^{2022}$, we get $$\Rightarrow (21 + 1)^{2022} = {}^{2022}C_{0}(21)^{2022} + {}^{2022}C_{1}(21)^{2021} + \ldots + {}^{2022}C_{2022}(1)^{2022}$$ $$= 3(3^{2021} \times 7^{2022} + {}^{2022}C_{1} \times 3^{2020} \times 7^{2021} + \ldots) + 1$$ $$= 3k_1 + 1$$ In this case the remainder is 1. Hence, $\alpha = 1$. Now, $$\Rightarrow (22)^{2022} + (2022)^{22} = (21 + 1)^{2022} + (2023 - 1)^{22}$$ Take $(2023 - 1)^{22}$ $$\Rightarrow (2023 - 1)^{22} = {}^{22}C_{0}(2023)^{22} - {}^{22}C_{1}(2023)^{21} + \ldots + {}^{22}C_{22}(-1)^{22}$$ $$= 7\left({}^{22}C_{0}(7)^{21}(289)^{22} - {}^{22}C_{1}(7)^{20}(289) + \ldots\right) + 1$$ $$= 7k_2 + 1$$ $$\Rightarrow (21 + 1)^{2022} + (2023 - 1)^{22} = 7k_1 + 1 + 7k_2 + 1$$ $$= 7\mu + 2$$ $$\Rightarrow \beta = 2.$$ Hence, $\alpha + \beta^2 = 1^2 + 2^2 = 5.$ Therefore, the required answer is 5.
Question 20
Maths · Statistics · Single correct
Let $\mu$ be the mean and $\sigma$ be the standard deviation of the distribution where $\sum f_i = 62$. If $[x]$ denotes the greatest integer $\leq x$, then $[\mu^2+\sigma^2]$ is equal
9
8
7
6
Answer: (b)
Solution
Given, Now we know that, Mean = $\frac{\sum X_i f_i}{\sum f_i}$ $\Rightarrow$ $\mu$ = $\frac{2k + 2k^2 - 2 + 3k^2 - 3 + 4k^2 + 4 - 5k - 15}{62}$ $\Rightarrow$ $\mu$ = $\frac{9k^2 + 7k - 16}{62}$ $\ldots$ $\ldots$ (1) And $\sum$ f_i = 62 $\Rightarrow$ 3k^2 + 4k - 2 = 62 $\Rightarrow$ 3k^2 + 4k - 64 = 0 $\Rightarrow$ (3k + 16)(k - 4) = 0 $\Rightarrow$ k = 4 Now putting the value of k in above equation (1) we get, $\mu$ = $\frac{156}{62}$ Now finding variance we get, $\sigma$^2 = $\frac{\sum (X_i)^2 f_i}{\sum f_i}$ - (Mean)^2 $\Rightarrow$ $\sigma$^2 = $\frac{1 \cdot (2k) + 4(k^2 - 1) + 9(k^2 - 1) + 16(k^2 + 1) + 25(k - 3)}{62}$ - $\left$($\frac{156}{62}$$\right$)^2 $\Rightarrow$ $\sigma$^2 = $\frac{29k^2 + 27k - 72}{62}$ - $\mu$^2 Now putting the value of k in above equation we get, $\Rightarrow$ $\sigma$^2 = $\frac{500}{62}$ - $\mu$^2 $\Rightarrow$ $\sigma$^2 + $\mu$^2 = $\frac{500}{62}$ $\Rightarrow$ [$\sigma$^2 + $\mu$^2] = 8
Question 21
Maths · Straight Lines and Pair of Straight Lines · Numerical
Let the equations of two adjacent sides of a parallelogram $ABCD$ be $2x - 3y = -23$ and $5x + 4y = 23$. If the equation of its one diagonal $AC$ is $3x + 7y = 23$ and the distance of $A$ from the other diagonal is $d$, then $50d^2$ is equal to
Answer: 529
Solution
Given, the equations of two adjacent sides of a parallelogram $ABCD$ be $2x - 3y = -23$ and $5x + 4y = 23$. So, $AB \equiv 2x - 3y = -23$ and $BC \equiv 5x + 4y = 23$. Also given, $AC \equiv 3x + 7y = 23$. Solving the above lines we get, $A(-4, 5)$, $B(-1, 7)$, $C(3, 2)$. We know that, diagonals of a parallelogram have the same midpoint, so $AC$ and $BD$ have the same midpoint and let point $D$ be $(x, y)$. So midpoint formula we get, $$\frac{x - 1}{2} = \frac{-4 + 3}{2} \Rightarrow x = 0 and \frac{y + 7}{2} = \frac{2 + 5}{2} \Rightarrow y = 0$$ Hence, point $D$ is $(0, 0)$. Now equation of $BD$ will be $7x + y = 0$. Now finding the distance of $A(-4, 5)$ from $7x + y = 0$ we get, $$d = \left| \frac{7(-4) + 5}{\sqrt{7^2 + 1^2}} \right| = \frac{23}{\sqrt{50}}$$ Hence, $50d^2 = 23^2 = 529$
Question 22
Maths · Determinants · Numerical
Let $S$ be the set of values of $\lambda$, for which the system of equations $$6\lambda x - 3y + 3z = 4\lambda^2, 2x + 6\lambda y + 4z = 1 and 3x + 2y + 3\lambda z = \lambda$$ has no solution. Then, $12 \sum_{\lambda \in S} |\lambda|$ is equal to _______.
Answer: 24
Solution
Given, system of equations, $$6 \lambda x - 3y + 3z = 4 \lambda^2$$ $$2x + 6 \lambda y + 4z = 1$$ $$3x + 2y + 3 \lambda z = \lambda$$ For no solution $\Delta = 0$, $$\begin{vmatrix} 6 \lambda & -3 & 3 \\ 2 & 6 \lambda & 4 \\ 3 & 2 & 3 \lambda \end{vmatrix} = 0$$ So, $$9 \lambda^3 - 7 \lambda - 2 = 0$$ $$\Rightarrow (\lambda - 1)(3 \lambda + 1)(3 \lambda + 2) = 0$$ Hence, $$\lambda \in \left\{ 1, -\frac{1}{3}, -\frac{2}{3} \right\}$$ Now putting the value of $\lambda$ in $12 \sum_{\lambda \in S} |\lambda|$ we get, $$12 \sum_{\lambda \in S} |\lambda| = 12 \times \left( 1 + \frac{1}{3} + \frac{2}{3} \right) = 24$$
Question 23
Maths · Three Dimensional Geometry · Numerical
Let the foot of perpendicular from the point $A(4, 3, 1)$ on the plane $P: x - y + 2z + 3 = 0$ be $N$. If $B(5, \alpha, \beta)$, $\alpha, \beta \in \mathbb{Z}$ is a point on plane $P$ such that the area of the triangle $ABN$ is $3\sqrt{2}$, then $\alpha^2 + \beta^2 + \alpha\beta$ is equal to
Answer: 7
Solution
Given, the foot of perpendicular from the point $A(4, 3, 1)$ on the plane $P: x - y + 2z + 3 = 0$ be $N$. So, by foot of perpendicular formula we get, $$\frac{x_1 - 4}{1} = \frac{y_1 - 3}{-1} = \frac{z_1 - 1}{2} = \frac{-4 - 3 + 2 + 3}{1^2 + 1^2 + 2^2}$$ $$\Rightarrow N \equiv (x_1, y_1, z_1) = (3, 4, -1)$$ And $B(5, \alpha, \beta), \alpha, \beta \in \mathbb{Z}$ is a point on plane $P$ such that the area of the triangle $ABN$ is $3\sqrt{2}$. So putting the value of point $B(5, \alpha, \beta)$ in plane we get, $$5 - \alpha + 2\beta + 3 = 0$$ $$\Rightarrow \alpha - 2\beta = 8$$ And given area of triangle $ABN$ is $3\sqrt{2}$, we get $$\frac{1}{2} AN \times BN = 3\sqrt{2}$$ $$\Rightarrow AN \times BN = 6\sqrt{2}$$ $$\Rightarrow \frac{6}{\sqrt{6}} \times BN = 6\sqrt{2}$$ $$\Rightarrow BN = 2\sqrt{3}$$ $$\Rightarrow 4 + (\alpha - 4)^2 + (\beta + 1)^2 = 12$$ $$\Rightarrow (\alpha - 4)^2 + (\beta + 1)^2 = 8$$ $$\Rightarrow 5\beta^2 + 18\beta + 9 = 0 \{as \alpha - 2\beta = 8\}$$ $$\Rightarrow \beta = -3 \left\{as \beta \neq -\frac{3}{5}\right\}$$ So, $\beta = -3$, $\alpha = 2$. Hence, $\alpha^2 + \beta^2 + \alpha\beta = 3^2 + 2^2 - 6 = 7$
Question 24
Maths · Applications of Derivatives · Numerical
Let the quadratic curve passing through the point $(-1,0)$ and touching the line $y = x$ at $(1,1)$ be $y = f(x)$. Then the $x$-intercept of the normal to the curve at the point $(\alpha, \alpha + 1)$ in the first quadrant is
Answer: 11
Solution
Given, the quadratic curve passing through the point $(-1, 0)$ and touching the line $y = x$ at $(1, 1)$ be $y = f(x)$. Now let the curve be $y = ax^2 + bx + c$. Passes through $(-1, 0)$ $$\Rightarrow a - b + c = 0 \ldots (i)$$ Passes through $(1, 1)$ $$\Rightarrow a + b + c = 1 \ldots (ii)$$ Now given tangent to $y = x$ at $(1, 1)$, so, $$\frac{dy}{dx} = 1$$ $$\Rightarrow 2a + b = 1 \ldots (iii)$$ Solving all above three equations we get, $$a = \frac{1}{4}, \; b = \frac{1}{2} \; and \; c = \frac{1}{4}$$ Hence, the equation of curve is $y = \frac{x^2}{4} + \frac{x}{2} + \frac{1}{4}$. Now $(\alpha, \alpha + 1)$ lies on curve $$\alpha + 1 = \frac{\alpha^2}{4} + \frac{\alpha}{2} + \frac{1}{4}$$ $$\Rightarrow (\alpha - 3)(\alpha + 1) = 0$$ $$\Rightarrow \alpha = 3$$ Point in first quadrant is $(3, 4)$. Now finding slope of tangent at $(3, 4)$ we get, $$\left( \frac{dy}{dx} \right)_{(3,4)} = \left( \frac{x}{2} + \frac{1}{2} \right)_{(3,4)} = 2$$ $$\Rightarrow Slope of normal = -\frac{1}{2}$$ Hence, equation of normal will be, $$y - 4 = -\frac{1}{2}(x - 3)$$ So, $x$-intercept $= 11$
Question 25
Maths · Differential Equations · Numerical
Let the tangent at any point P on a curve passing through the points (1, 1) and ( $\frac{1}{10}$, 100), intersect positive x-axis and y-axis at the points A and B respectively. If $PA : PB = 1 : k$ and $y = y(x)$ is the solution of the differential equation $e^{\frac{dy}{dx}} = kx + \frac{k}{2}$, $y(0) = k$, then $4y(1) - 5 \log_e 3$ is equal to
Answer: 5
Solution
Given, the tangent at any point P on a curve passing through the points $(1, 1)$ and $\left( \frac{1}{10}, 100 \right)$, intersect positive x-axis and y-axis at the points A and B respectively. And $PA : PB = 1 : 1$. $k$ and $y = y(x)$ is the solution of the differential equation $\frac{dy}{dx} = kx + \frac{k}{2}$, $y(0) = k$. Now on plotting the diagram we get, Equation of tangent at $P(x, y)$ is: $$Y - y = \frac{dy}{dx} (X - x)$$ Coordinate of $A = \left( x - y \frac{dy}{dx}, 0 \right)$ Coordinate of $B = \left( 0, y - x \frac{dy}{dx} \right)$ $$\therefore (x, y) = \left( \frac{kx - ky}{k + 1}, \frac{y - x \frac{dy}{dx}}{k + 1} \right)$$ So, $y = \frac{y - x \frac{dy}{dx}}{k + 1}$ $$\Rightarrow y(k + 1) = y - x \frac{dy}{dx}$$ $$\Rightarrow ky = -x \frac{dy}{dx}$$ $$\Rightarrow k \frac{dz}{z} = - \frac{dx}{x}$$ Now integrating both sides, we get $$k \ln |x| + \ln |y| = \ln C \ldots (i)$$ Now given equation (i) passes through $(1, 1)$ and $\left( \frac{1}{10}, 100 \right)$ So, $C = 1$ and $k = 2$ Now putting the value of $k$, we get $$e^{\frac{dy}{dx}} = kx + \frac{k}{2}$$ $$\Rightarrow e^{\frac{dy}{dx}} = 2x + 1 \{as k = 2\}$$ $$\Rightarrow \frac{dy}{dx} = \ln(2x + 1)$$ Integrating the above equation we get, $$y = \frac{1}{2}(2x + 1)[\ln(2x + 1) - 1] + C$$ And the above equation passes through $(0, 2)$ So, $C = \frac{5}{2}$ So, $2y = (2x + 1)(\ln(2x + 1) - 1) + 5$ $$\Rightarrow 2y(1) = 3(\ln 3 - 1) + 5$$ $$\Rightarrow 2y(1) = 3 \ln(3) + 2$$ Hence, $4y(1) - 5 \ln 3 = 3$, $2 = 3(2 \ln 3 - 1) - 5 \ln 3$ $$\Rightarrow 4y(1) - 5 \ln 3 = 6 \ln 3 + 4 - 5 \ln 3 = 13$$ $$\Rightarrow 4y(1) - 5 \ln 3 = 4 - \ln 3 \approx 5$$ Note: This question was found in JEE Mains 2023 April session.
Question 26
Maths · Sequences and Series · Numerical
Suppose $a_1, a_2, 2, a_3, a_4$ be in an arithmetico-geometric progression. If the common ratio of the corresponding geometric progression is $2$ and the sum of all 5 terms of the arithmetico-geometric progression is $\frac{49}{2}$, then $a_4$ is equal to
Answer: 16
Solution
Given, $a_1, a_2, 2, a_3, a_4$ be in an arithmetico-geometric progression. And the common ratio of the corresponding geometric progression is 2 and the sum of all 5 terms of the arithmetico-geometric progression is $\frac{49}{2}$. So, common ratio here $r = 2$ and let common difference $= d$. And we know that, $$a_2 = (a_1 + d) \times 2$$ $$2 = (a_1 + 2d) \times 2^2 \ldots (i)$$ $$a_3 = (a_1 + 3d) \times 2^3$$ $$a_4 = (a_1 + 4d) \times 2^4$$ Now adding all above equations we get, $$31a_1 + 98d = \frac{49}{2} \ldots (ii)$$ Now from $(i)$ and $(ii)$ $$a_1 = 2, d = \frac{1}{4}$$ Hence, $a_4 = 16(0 + 1) = 16$
Question 27
Maths · Relations and Functions · Numerical
If the domain of the function $f(x) = \sec^{-1}\left(\frac{2x}{5x+3}\right)$ is $[\alpha, \beta) \cup (\gamma, \delta]$, then $|3\alpha + 10(\beta + \gamma) + 21\delta|$ is equal to
Answer: 24
Solution
We know that, Domain of $\sec^{-1} x$ is $(-\infty, -1] \cup [1, \infty)$. Now, $f(x) = \sec^{-1} \left( \frac{2x}{5x+3} \right)$. So, $$\frac{2x}{5x+3} \leq -1 or \frac{2x}{5x+3} \geq 1$$ $$\Rightarrow \frac{2x}{5x+3} + 1 \leq 0 or \frac{2x}{5x+3} - 1 \geq 0$$ $$\Rightarrow \frac{7x+3}{5x+3} \leq 0 or \frac{-3x-3}{5x+3} \geq 0$$ $$\Rightarrow \frac{7x+3}{5x+3} \leq 0 or \frac{x+1}{5x+3} \leq 0$$ $$\Rightarrow x \in \left[ -1, -\frac{3}{5} \right) \cup \left( -\frac{3}{5}, -\frac{3}{7} \right]$$ So, $\alpha = -1$, $\beta = -\frac{3}{5}$, $\gamma = -\frac{3}{5}$, $\delta = -\frac{3}{7}$. Now, $$|3\alpha + 10(\beta + \gamma) + 21\delta|$$ $$= |-3 - 6 - 6 - 9|$$ $$= 24$$ Hence this is the required answer.
Question 28
Maths · Permutations and Combinations · Numerical
The sum of all the four-digit numbers that can be formed using all the digits 2, 1, 2, 3 is equal to ____.
In the figure, $\theta_1 + \theta_2 = \frac{\pi}{2}$ and $\sqrt{3}(\mathrm{BE})=4(\mathrm{AB})$. If the area of $\triangle \mathrm{CAB}$ is $2\sqrt{3} - 3 \, \mathrm{unit}^2$, when $\frac{\theta_2}{\theta_1}$ is the largest, then the perimeter (in unit) of $\triangle \mathrm{CED}$ is equal to
Answer: 6
Solution
Given, And $\theta_1 + \theta_2 = \frac{\pi}{2}$. Now, Let $AB = x$, $BD = y$. Also given, $\sqrt{3}BE = 4AB$ $$\Rightarrow \sqrt{3}(y + DE) = 4x$$ $$\Rightarrow DE = \frac{4x}{\sqrt{3}} - y$$ Now given area of triangle $\Delta CAB = 2\sqrt{3} - 3$ $$\Rightarrow \frac{1}{2} xy = 2\sqrt{3} - 3$$ $$\Rightarrow y = \frac{4\sqrt{3} - 6}{x}$$ Now finding, $\tan \theta_2 = \frac{x}{y} = \frac{x^2}{4\sqrt{3}} = \frac{4}{\sqrt{3}} \left( \frac{4\sqrt{3} - 6}{x^2} \right)$ $\tan \theta_1 = \frac{y}{x} = \frac{4\sqrt{3} - 6}{x^2}$ Now taking tan both of $\theta_1 + \theta_2 = \frac{\pi}{2}$ we get, $\tan \theta_1 \cdot \tan \theta_2 = 1$ $$\Rightarrow \left( \frac{4}{\sqrt{3}} \right) \left( \frac{4\sqrt{3} - 6}{x^2} \right) = 1$$ $$\Rightarrow \frac{4\sqrt{3} - 6}{x^2} = \sqrt{3} or \frac{4\sqrt{3} - 6}{x^2} = \frac{1}{\sqrt{3}}$$ So, $\theta_1$ is maximum when $\frac{4\sqrt{3} - 6}{x^2} = \frac{1}{\sqrt{3}}$ $$\Rightarrow x^2 = \sqrt{3} (4\sqrt{3} - 6)$$ $$\Rightarrow x^2 = 12 - 6\sqrt{3}$$ $$\Rightarrow x^2 = (3 - \sqrt{3})$$ $$\Rightarrow x = 3 - \sqrt{3} and \angle C = 60^\circ$$ $$\Rightarrow \tan 60^\circ = \frac{DE}{CD} = \frac{DE}{CE} = x : \sqrt{3} = 3\sqrt{3} - 3$$ And $\cos 60^\circ = \frac{CD}{CE} = \frac{2x - 6}{2\sqrt{3}}$ So, the Perimeter of $\Delta AEC = CD + DE + CE = 6$
Question 30
Maths · Applications of Integrals · Numerical
If the area of the region $\{(x, y) : |x^2 - 2| \leq y \leq x \}$ is $A$, then $6A + 16\sqrt{2}$ is equal to
Answer: 27
Solution
If the area of the region $\{(x, y) : |x^2 - 2| \leq y \leq x \}$ is $A$, then $6A + 16\sqrt{2}$ is equal to $_$ Given, $$|x^2 - 2| \leq y \leq x$$ Now on finding the intersection point we get, $(x, y) \equiv (1, 1)$ and $(2, 2)$ Now plotting the curve of the above function we get, Now from above diagram required bounded area will be, A = ∫[1 to √2] (x - (2 - x²)) dx + ∫[√2 to 2] (x - (x² - 2)) dx A = [x²/2 - 2x + x³/3]₁^√2 + [x²/2 - x³/3 + 2x]√2^2 A = [1 - 2√2/3] - [-7/6] + [10/3] - [1 - 2√2/3 + 2√2] A = 9/2 - 8√2/3 ⇒ 6A = 27 - 16√2 ⇒ 6A + 16√2 = 27
Physics
Question 31
Physics · Motion in a Straight Line · Single correct
A person travels $x$ distance with velocity $v_1$ and then $x$ distance with velocity $v_2$ in the same direction. The average velocity of the person is $v$, then the relation between $v$, $v_1$ and $v_2$ will be
$v = \frac{v_1 + v_2}{2}$
$\frac{1}{v} = \frac{1}{v_1} + \frac{1}{v_2}$
$v = v_1 + v_2$
$\frac{2}{v} = \frac{1}{v_1} + \frac{1}{v_2}$
Answer: (d)
Solution
The time ($t_1$) taken by the person to travel distance $x$ with velocity $v_1$ is given by $$t_1 = \frac{x}{v_1} \ldots(1)$$ The time ($t_2$) taken by the person to travel distance $x$ with velocity $v_2$ is given by $$t_2 = \frac{x}{v_2} \ldots(2)$$ The formula to calculate the average speed ($v$) of the person is given by $$v = \frac{2x}{t_1 + t_2} \ldots(3)$$ Substitute the expressions from equations (1) and (2) into equation (3) to obtain the required relation. $$v = \frac{2x}{\left( \frac{x}{v_1} + \frac{x}{v_2} \right)}$$ $$\Rightarrow \frac{x}{v_1} + \frac{x}{v_2} = \frac{2x}{v}$$ $$\Rightarrow \frac{2}{v} = \frac{1}{v_1} + \frac{1}{v_2}$$
Question 32
Physics · Nuclei · Single correct
The half life of a radioactive substance is $T$. The time taken, for disintegrating $\left( \frac{7}{8} \right)^{th}$ part of its original mass will be:
$2T$
$3T$
$T$
$8T$
Answer: (b)
Solution
It is given that $t_{\frac{1}{2}} = T$. After disintegration of $\left( \frac{7}{8} \right)^{th}$ part, $\left( \frac{1}{8} \right)^{th}$ part is only left. Using the decay formula, $$N = N_0 \left( \frac{1}{2} \right)^{\frac{t}{t_{\frac{1}{2}}}}$$ $$\Rightarrow \frac{N_0}{8} = N_0 \left( \frac{1}{2} \right)^{\frac{t}{T}}$$ $$\Rightarrow -\ln 8 = -\frac{t}{T} \ln 2$$ $$\Rightarrow 3 \ln 2 = \frac{t}{T} \ln 2$$ $$\Rightarrow t = 3T$$
Question 33
Physics · Kinetic Theory · Single correct
A gas mixture consists of 2 moles of oxygen and 4 moles of neon at temperature $T$. Neglecting all vibrational modes, the total internal energy of the system will be:
11RT
8RT
4RT
16RT
Answer: (a)
Solution
The internal energy of a gas is given by $U = nC_V T$. A diatomic gas has 3 translational and 2 rotational degrees of freedom. A monoatomic gas has 3 translational degrees of freedom. Hence, the internal energy of the mixture $= n_1 C_{V_1} T + n_2 C_{V_2} T$ $$= 2 \times \left( \frac{5R}{2} \right) T + 4 \times \frac{3R}{2} T$$ $$= 5RT + 6RT$$ $$= 11RT$$
Question 34
Physics · Experimental Physics · Single correct
In an experiment with vernier callipers of least count $0.1 \, \mathrm{mm}$, when two jaws are joined together the zero of vernier scale lies right to the zero of the main scale and $6^{th}$ division of vernier scale coincides with the main scale division. While measuring the diameter of a spherical bob, the zero of vernier scale lies in between $3.2 \, \mathrm{cm}$ and $3.3 \, \mathrm{cm}$ marks and $4^{th}$ division of vernier scale coincides with the main scale division. The diameter of bob is measured as
3.22 cm
3.18 cm
3.26 cm
3.25 cm
Answer: (b)
Solution
The least count is $LC = 0.1 \, \mathrm{mm}$. Zero error $(ZE) = 6 \times LC = 6 \times 0.1 \, \mathrm{mm} = 0.6 \, \mathrm{mm}$. The total reading is $$TR = MSR + (VSR \times LC) - ZE$$ $$\Rightarrow TR = 32 \, \mathrm{mm} + (0.1 \times 4) \, \mathrm{mm} - 0.6 \, \mathrm{mm}$$ $$\Rightarrow TR = 31.8 \, \mathrm{mm} = 3.18 \, \mathrm{cm}$$
Question 35
Physics · Magnetism and Matter · Single correct
Given below are two statements: Statement I: For diamagnetic substance $-1 \leq x < 0$, where $x$ is the magnetic susceptibility. Statement II: Diamagnetic substance when placed in an external magnetic field, tend to move from stronger to weaker part of the field. In the light of the above statements, choose the correct answer from the options give below.
Both Statement I and Statement II are False
Statement I is correct but Statement II is false
Statement I is incorrect but Statement II is true
Both Statement I and Statement II are true
Answer: (d)
Solution
There are no atomic dipoles in diamagnetic materials because the resultant magnetic moment of each atom is zero due to paired electrons. Diamagnetic materials are repelled by a magnet. These substances are weakly repelled by the field, so in a nonuniform field, these substances have a tendency to move from a strong to a weak part of the external magnetic field. For diamagnetic substance $(-1 < \chi < 0)$ and a diamagnetic substance is repelled by the magnetic field.
Question 36
Physics · Electrostatic Potential and Capacitance · Single correct
The distance between two plates of a capacitor is $d$ and its capacitance is $C_1$, when air is the medium between the plates. If a metal sheet of thickness $\frac{2d}{3}$ and of the same area as plate is introduced between the plates, the capacitance of the capacitor becomes $C_2$. The ratio $\frac{C_2}{C_1}$ is
3 : 1
2 : 1
4 : 1
1 : 1
Answer: (a)
Solution
The formula of capacitance is $C_1 = \left( \frac{\varepsilon_0 A}{d} \right)$. The dielectric constant of the metal sheet is $K_{metal} = \infty$. The new value of capacitance is $$C_2 = \frac{\varepsilon_0 A}{d + \frac{t}{K_{metal}}} = \frac{\varepsilon_0 A}{\frac{2d}{3} + 0} = 3C_1.$$ Clearly, the ratio, $$\frac{C_2}{C_1} = \frac{3C_1}{C_1} = 3 : 1.$$
Question 37
Physics · Gravitation · Single correct
Given below are two statements: Statement I: Rotation of the earth shows effect on the value of acceleration due to gravity $(g)$. Statement II: The effect of rotation of the earth on the value of $g$ at the equator is minimum and that at the pole is maximum. In the light of the above statements, choose the correct answer from the options given below
Statement I is false but statement II is true
Both Statement I and Statement II are true
Both Statement I and Statement II are false
Statement I is true but statement II is false
Answer: (d)
Solution
The variation of acceleration due to gravity with the rotation of Earth can be written as $$g' = g - \omega^2 R \cos^2 \lambda \ldots (1)$$ Substitute $0^\circ$ for $\lambda$ for equatorial position to obtain the acceleration due to gravity. $$g' = g - \omega^2 R \cos^2 0^\circ$$ $$= g - \omega^2 R$$ Substitute $90^\circ$ for $\lambda$ for polar position to obtain the acceleration due to gravity. $$g' = g - \omega^2 R \cos^2 90^\circ$$ $$= g$$ The above two equations show that the effect on acceleration due to gravity is maximum at the equator and minimum at pole.
Question 38
Physics · Gravitation · Single correct
The time period of a satellite, revolving above earth's surface at a height equal to R will be (Given $g = \pi^2 \, \mathrm{m \, s^{-2}}$, $R = radius of earth$)
$\sqrt{2R}$
$\sqrt{8R}$
$\sqrt{32R}$
$\sqrt{4R}$
Answer: (c)
Solution
The velocity of the satellite revolving round the Earth at a height $r$ from the centre of the Earth is given by $$v = \sqrt{\left( \frac{GM}{r} \right)} \ldots (1)$$ The formula to calculate the time period in the circular orbit is given by $$T = \frac{2 \pi r}{v} \ldots (2)$$ In this case: $r = R + R = 2R$ Substitute the expression for the velocity from equation (1) into equation (2) and simplify to obtain the required time period. $$T = \frac{2 \pi r}{\sqrt{\frac{GM}{r}}}$$ $$= \frac{2 \pi \times 2R}{\sqrt{\frac{gR}{2}}}$$ $$= \frac{4 \pi R \sqrt{2}}{\pi \sqrt{R}}$$ $$= 4 \sqrt{2R}$$ $$= \sqrt{32R}$$
Question 39
Physics · Laws of Motion · Single correct
Given below are two statements: one is labelled as Assertion A and the other is labelled as Reason R Assertion A : An electric fan continues to rotate for some time after the current is switched off. Reason R: Fan continues to rotate due to inertia of motion. In the light of above statements, choose the most appropriate answer from the options given below.
A is correct but R is not correct
A is not correct but R is correct
Both A and R are correct and R is the correct explanation of A
Both A and R are correct but R is NOT the correct explanation of A
Answer: (c)
Solution
When a fan is rotating, it acquires some kinetic energy. When the switch is off, because of its motion, it continues rotating for some time until it stops because of the air friction. So it is due to inertia of motion that fan continues to rotate. Hence, both A and R are correct and R is the correct explanation of A.
Question 40
Physics · Electromagnetic Waves · Single correct
The amplitude of magnetic field in an electromagnetic wave propagating along $y$-axis is $6.0 \times 10^{-7} \, \mathrm{T}$. The maximum value of electric field in the electromagnetic wave is
The relation between the electric field and magnetic field is given by $E_0 = c B_0$. The given data is $B_0 = 6 \times 10^{-7} \, \mathrm{T}$ and $c = 3 \times 10^8 \, \mathrm{m \, s^{-1}}$. Thus, the maximum value of the electric field is $$E_0 = (3 \times 10^8) \times (6 \times 10^{-7}) = 180 \, \mathrm{V \, m^{-1}}.$$
Question 41
Physics · Thermodynamics · Single correct
A gas is compressed adiabatically, which one of the following statement is NOT true?
There is no heat supplied to the system
There is no change in the internal energy
The temperature of the gas increases
The change in the internal energy is equal to the work done on the gas
Answer: (b)
Solution
In adiabatic process, $\Delta Q = 0$ and $\Delta U \neq 0$. Using the first law of thermodynamics, $\Delta Q = \Delta U + W$. Therefore, $\Delta U = -W$ ($W$ is the work done by the gas, so $-W$ will be the work done on the gas). As the gas is compressed $W 0$ and hence $\Delta T > 0$.
Question 42
Physics · Wave Optics · Single correct
The ratio of intensities at two points P and Q on the screen in a Young's double slit experiment where phase difference between two waves of same amplitude are $\frac{\pi}{3}$ and $\frac{\pi}{2}$, respectively are
2 : 3
1 : 3
3 : 1
3 : 2
Answer: (d)
Solution
The formula to calculate the intensity of the interference pattern in Young's double slit experiment can be written as $$I = 4I_0 \cos^2 \left( \frac{\phi}{2} \right) \cdots (1)$$ Hence, the ratio of the required intensities can be calculated as follows- $$\frac{I_1}{I_2} = \frac{4I_0 \cos^2 \left( \frac{\pi}{6} \right)}{4I_0 \cos^2 \left( \frac{\pi}{4} \right)}$$ $$= \frac{\frac{3}{4}}{\frac{1}{2}}$$ $$= \frac{3}{2}$$
Question 43
Physics · Dual Nature of Radiation and Matter · Single correct
The variation of stopping potential $(V_0)$ as a function of the frequency $(\nu)$ of the incident light for a metal is shown in figure. The work function of the surface is
2.98 eV
2.07 eV
1.36 eV
18.6 eV
Answer: (b)
Solution
The relation between the stopping potential and the frequency of the incident light is given by $$eV_0 = h\nu - \phi \ldots (1)$$ When $V_0 = 0$, $$\phi = h\nu \ldots (2)$$ Substitute the value of the frequency corresponding to zero stopping potential into equation (2) to calculate the required work function of the material. $$\phi = \frac{6.626 \times 10^{-34} \, \mathrm{J\cdot s} \times 5 \times 10^{14} \, \mathrm{Hz}}{1.6 \times 10^{-19} \, \mathrm{J/eV}}$$ $$= \frac{6.626 \times 5}{16} \approx 2.07 \, \mathrm{eV}$$
Question 44
Physics · Oscillations · Single correct
For a periodic motion represented by the equation $y = \sin \omega t + \cos \omega t$ the amplitude of the motion is
1
0.5
2
\sqrt{2}
Answer: (d)
Question 45
Physics · Current Electricity · Single correct
In a metallic conductor, under the effect of applied electric field, the free electrons of the conductor
Drift from higher potential to lower potential
Move with the uniform velocity throughout from lower potential to higher potential
Move in the straight line paths in the same direction
Move in the curved paths from lower potential to higher potential
Answer: (d)
Solution
The electrons inside the conductor move with an average velocity due to the applied field in a direction opposite to the field, this velocity is known as drift velocity. Electric field are applied from high to low potential region of the conductor. Also, electrons are negatively charged. Electron drifts from lower potential to higher potential on curved path.
Question 46
Physics · Mechanical Properties of Solids · Single correct
Young's moduli of the material of wires A and B are in the ratio of 1 : 4, while its area of cross sections are in the ratio of 1 : 3. If the same amount of load is applied to both the wires, the amount of elongation produced in the wires A and B will be in the ratio of [Assume length of wires A and B are same]
12 : 1
1 : 36
36 : 1
1 : 12
Answer: (a)
Solution
The formula to calculate the elongation of a metallic wire because of the application of a load can be written as $$\Delta L = \left( \frac{FL}{AY} \right) \ldots (1)$$ The ratio of the elongations for both the wires is, then, calculated as follows- $$\frac{\Delta L_1}{\Delta L_2} = \frac{\frac{FL}{A_1Y_1}}{\frac{FL}{A_2Y_2}}$$ $$= \frac{A_2Y_2}{A_1Y_1}$$ $$= \frac{3}{1} \times \frac{4}{1}$$ $$= \frac{12}{1}$$
Question 47
Physics · Motion in a Plane · Single correct
Two projectiles are projected at $30^\circ$ and $60^\circ$ with the horizontal with the same speed. The ratio of the maximum height attained by the two projectiles respectively is:
$\sqrt{3} : 1$
1 : $\sqrt{3}$
2 : $\sqrt{3}$
1 : 3
Answer: (d)
Solution
The maximum height is given by, $H = \frac{u^2 \sin^2 \theta}{2g}$. The given data is $\theta_1 = 30^\circ$, $\theta_2 = 60^\circ$, $u_1 = u_2$. Therefore, $$\frac{(H_1)_{\max}}{(H_2)_{\max}} = \frac{u_1^2 \sin^2 \theta_1}{u_2^2 \sin^2 \theta_2}$$ $$= \left(\frac{\sin 30^\circ}{\sin 60^\circ}\right)^2$$ $$= \left(\frac{\frac{1}{2}}{\frac{\sqrt{3}}{2}}\right)^2$$ $$= \left(\frac{1}{\sqrt{3}}\right)^2$$ $$= \frac{1}{3}$$
Question 48
Physics · Communication Systems · Single correct
A massage signal of frequency $3$ $\mathrm{kHz}$ is used to modulate a carrier signal of frequency $1.5$ $\mathrm{MHz}$. The bandwidth of the amplitude modulated wave is
$6 \mathrm{MHz}$
$6$ $\mathrm{kHz}$
$3$ $\mathrm{MHz}$
$3$ $\mathrm{kHz}$
Answer: (b)
Solution
The relation between bandwidth and the signal frequency is given by $$Bandwidth = 2 \times signal frequency (1)$$ Substitute the values of the known parameter into equation (1) to calculate the required bandwidth. $$Bandwidth = 2 \times 3 \, \mathrm{kHz}$$ $$= 6 \, \mathrm{kHz}$$
Question 49
Physics · Semiconductor Electronics: Materials, Devices and Simple Circuits · Single correct
If each diode has a forward bias resistance of $25\,\Omega$ in the below circuit,
$\frac{I_1}{I_2} = 1$
$\frac{I_2}{I_3} = 1$
$\frac{I_1}{I_2} = 2$
$\frac{I_3}{I_4} = 1$
Answer: (c)
Solution
As the diode $D_2$ is connected in reverse order, there is no current through it. The effective resistances of the circuit can, then, be calculated as follows: $$R_{eff} = 25 + \frac{(25 + 125)^2}{(25 + 125) + (25 + 125)} \, \Omega$$ $$= 100 \, \Omega$$ Each current through the diodes can be calculated as follows: $$I_1 = \left( \frac{5 \, \mathrm{V}}{100 \, \Omega} \right)$$ $$= 0.05 \, \mathrm{A}$$ As the diode $D_2$ is non-conducting, the current $I_1$ will be divided equally among the other two diodes $D_1$ and $D_3$. Hence, the currents in the diodes can be written as $$I_2 = \frac{0.05 \, \mathrm{A}}{2}$$ $$= 0.025 \, \mathrm{A}$$ $$I_4 = 0.025 \, \mathrm{A}$$ Thus, $$\frac{I_1}{I_2} = \frac{0.05 \, \mathrm{A}}{0.025 \, \mathrm{A}}$$ $$= 2$$
Question 50
Physics · Magnetism and Matter · Single correct
A bar magnet is released from rest along the axis of a very long vertical copper tube. After some time the magnet will
Move down with an acceleration equal to $g$
Oscillate inside the tube
Move down with almost constant speed
Move down with an acceleration greater than $g$
Answer: (c)
Solution
The flux connected to the copper tube will fluctuate when the magnet moves under the influence of gravity. Eddy currents will be created in the copper tube's body as a result, these induced currents oppose the collapse of the magnet, in accordance with Lenz's law. A retarding force will consequently act on the magnet. This force will keep rising with the magnet's rising velocity until it equals the force of gravity. The net force acting on the magnet will then vanish. The magnet will therefore reach a steady speed.
Question 51
Physics · Electromagnetic Induction · Numerical
A square loop of side $2.0 \, \mathrm{cm}$ is placed inside a long solenoid that has $50$ turns per centimetre and carries a sinusoidally varying current of amplitude $2.5 \, \mathrm{A}$ and angular frequency $700 \, \mathrm{rad} \, \mathrm{s}^{-1}$. The central axes of the loop and solenoid coincide. The amplitude of the emf induced in the loop is $x \times 10^{-4} \, \mathrm{V}$. The value of $x$ is (Take, $\pi = \frac{22}{7}$)
Answer: 44
Solution
It is given that the current is varying sinusoidally. The current can be written as $I = I_0 \sin \omega t$. The magnetic field through the solenoid $B = \mu_0 n I$. The flux through the square is $\phi = \mu_0 n I A$. The emf is $$\varepsilon = \mu_0 n A \times \frac{d(I_0 \sin \omega t)}{dt}$$ $$\Rightarrow \varepsilon = \mu_0 n A I_0 \omega \cos \omega t$$ The amplitude of the emf is, $$\varepsilon = \mu_0 n A I_0 \omega = 4 \pi \times 10^{-7} \times \frac{50}{10^{-2}} \times 4 \times 10^{-4} \times 2.5 \times 700$$ $$\Rightarrow \varepsilon = 44 \times 10^{-4} \, \mathrm{V}$$
Question 52
Physics · Oscillations · Fill in the blank
A rectangular block of mass 5 kg attached to a horizontal spiral spring executes simple harmonic motion of amplitude 1 m and time period 3.14 s. The maximum force exerted by spring on block is ___ N.
Answer: 20
Solution
By Newton's second law, $F = ma_{max}$. The maximum acceleration for a SHM is given by $a_{max} = \omega^2 A \cdots (i)$. The time period is given by $$T = \frac{2\pi}{\omega} = 3.14 \, \mathrm{s}$$ $$\Rightarrow \omega = \frac{2\pi}{T} = \frac{2\pi}{3.14} = 2 \, \mathrm{rad} \, \mathrm{s}^{-1}$$ Thus, the maximum acceleration from equation (i) $$a_{max} = 4 \times 1 = 4 \, \mathrm{m} \, \mathrm{s}^{-2}$$ The maximum force is $$F = 5 \, \mathrm{kg} \times 4 \, \mathrm{m} \, \mathrm{s}^{-2} = 20 \, \mathrm{N}$$
Question 53
Physics · Atoms · Numerical
If $917 \, \mathrm{\AA}$ be the lowest wavelength of Lyman series then the lowest wavelength of Balmer series will be $\mathrm{\AA}$.
Physics · Mechanical Properties of Fluids · Numerical
Figure below shows a liquid being pushed out of the tube by a piston having area of cross section $2.0 \, \mathrm{cm}^2$. The area of cross section at the outlet is $10 \, \mathrm{mm}^2$. If the piston is pushed at a speed of $4 \, \mathrm{cm} \, \mathrm{s}^{-1}$, the speed of outgoing fluid is $\mathrm{cm} \, \mathrm{s}^{-1}$
Answer: 80
Solution
The given data is $A_1 = 2 \times 10^{-4} \, \mathrm{m^2}$ $A_2 = 10 \times 10^{-6} \, \mathrm{m^2}$ $v_1 = 4 \, \mathrm{cm \, s^{-1}}$ Using equation of continuity which is a conservation of mass principle, $$A_1 v_1 = A_2 v_2$$ $$\Rightarrow \; v_2 = \frac{A_1 v_1}{A_2} = \frac{2 \times 10^{-4} \times 4}{10 \times 10^{-6}}$$ $$= 80 \, \mathrm{cm \, s^{-1}}$$
Question 55
Physics · Moving Charges and Magnetism · Numerical
A straight wire carrying a current of 14 A is bent into a semicircular arc of radius 2.2 cm as shown in the figure. The magnetic field produced by the current at the centre $O$ of the arc is ____ $\times 10^{-4}$ T
Answer: 2
Solution
It is given that $i = 14 \, \mathrm{A}$ and $R = 2.2 \times 10^{-2} \, \mathrm{m}$. The magnetic field at the centre $O$ is given by $$B = \frac{\mu_0 i}{4R}$$ $$= \frac{4\pi \times 10^{-7} \times 14}{4 \times 2.2 \times 10^{-2}}$$ $$= 2 \times 10^{-4} \, \mathrm{T}$$
Question 56
Physics · Ray Optics and Optical Instruments · Numerical
A point object $O$ is placed in front of two thin symmetrical coaxial convex lenses $L_1$ and $L_2$ with focal length $24 \, \mathrm{cm}$ and $9 \, \mathrm{cm}$ respectively. The distance between two lenses is $10 \, \mathrm{cm}$ and the object is placed $6 \, \mathrm{cm}$ away from lens $L_1$ as shown in the figure. The distance between the object and the image formed by the system of two lenses is cm
A rectangular parallelopiped is measured as $1 \, \mathrm{cm} \times 1 \, \mathrm{cm} \times 100 \, \mathrm{cm}$. If its specific resistance is $3 \times 10^{-7} \, \Omega \, \mathrm{m}$, then the resistance between its two opposite rectangular faces will be _____ $\times 10^{-7} \, \Omega$.
Answer: 3
Solution
It is given that $l = 1 \, \mathrm{cm} = 0.01 \, \mathrm{m}$ $A = 100 \, \mathrm{cm} \times 1 \, \mathrm{cm} = 100 \, \mathrm{cm}^2$ $\Rightarrow A = 0.01 \, \mathrm{m}^2$ $\rho = 3 \times 10^{-7} \, \Omega \, \mathrm{m}$ Using the formula of resistance, $$R = \frac{\rho l}{A} = \frac{3 \times 10^{-7} \times 0.01}{0.01} = 3 \times 10^{-7} \, \Omega$$
Question 58
Physics · System of Particles and Rotational Motion · Numerical
A force of $-P \hat{k}$ acts on the origin of the coordinate system. The torque about the point $(2, -3)$ is $P \left( a \hat{i} + b \hat{j} \right)$. The ratio of $\frac{a}{b}$ is $\frac{x}{2}$. The value of $x$ is
Answer: 3
Solution
It is given that the force $\vec{F} = -P \hat{k}$. The coordinates of the origin is $(0, 0)$. The coordinates of the point given is $(2, -3)$. The displacement vector is $$\vec{r} = (0 - 2) \hat{i} + (0 + 3) \hat{j} = -2 \hat{i} + 3 \hat{j}$$ Hence, the torque is $$\vec{\tau} = \vec{r} \times \vec{F} = \begin{vmatrix} \hat{i} & \hat{j} & \hat{k} \\ -2 & 3 & 0 \\ 0 & 0 & -P \end{vmatrix}$$ $$\Rightarrow \vec{\tau} = -2P \hat{j} - 3P \hat{i} = P \left( a \hat{i} + b \hat{j} \right)$$ So, it can be written $a = -3, b = -2$ $$\therefore \frac{a}{b} = \left( \frac{3}{2} \right) \Rightarrow so x = 3$$
Question 59
Physics · Work, Energy and Power · Numerical
If the maximum load carried by an elevator is $1400 \, \mathrm{kg}$ ($600 \, \mathrm{kg}$-Passengers + $800 \, \mathrm{kg}$-elevator), which is moving up with a uniform speed of $3 \, \mathrm{m \, s^{-1}}$ and the frictional force acting on it is $2000 \, \mathrm{N}$, then the maximum power used by the motor is _______ $\mathrm{kW}$. ($g = 10 \, \mathrm{m \, s^{-2}}$)
Answer: 48
Solution
The maximum force acting is, $F_{max} = (14000 + 2000) \, \mathrm{N}$ $$= 16000 \, \mathrm{N}$$ The formula for power is given by, $P = F_{max} v$. It is given, $v = 3 \, \mathrm{m \, s^{-1}}$. $$\Rightarrow P = 16000 \, \mathrm{N} \times 3 \, \mathrm{m \, s^{-1}} = 48000 \, \mathrm{W} = 48 \, \mathrm{kW}$$ $$\Rightarrow W = 48 \, \mathrm{kW}$$
Question 60
Physics · Electric Charges and Fields · Numerical
An electron revolves around an infinite cylindrical wire having uniform linear charge density $2 \times 10^{-8} \, \mathrm{C \, m^{-1}}$ in circular path under the influence of attractive electrostatic field as shown in the figure. The velocity of electron with which it is revolving is _______ $\times 10^{6} \, \mathrm{m \, s^{-1}}$. Given mass of electron $= 9 \times 10^{-31} \, \mathrm{kg}$
Answer: 8
Solution
The electric field is given by $$E = \left( \frac{2k\lambda}{r} \right)$$ The required centripetal force is $$F = \left( \frac{mv^2}{r} \right)$$ The force due to the field is equal to the required centripetal force, $$\Rightarrow \left( \frac{2k\lambda}{r} \right) e = \frac{mv^2}{r}$$ $$\Rightarrow v = \sqrt{\frac{2k\lambda e}{m}}$$ $$= \sqrt{\frac{2 \times 9 \times 10^9 \times 2 \times 10^{-8} \times 1.6 \times 10^{-19}}{9 \times 10^{-31}}}$$ $$= \sqrt{1.6 \times 4 \times 10^{13}}$$ $$= 4 \times 2 \times 10^6 \, \mathrm{m} \, \mathrm{s}^{-1}$$ $$= 8 \times 10^6 \, \mathrm{m} \, \mathrm{s}^{-1}$$
Chemistry
Question 61
Chemistry · Alcohols, Phenols and Ethers · Single correct
Incorrect method of preparation for alcohols from the following is:
Reaction of Ketone with RMgBr followed by hydrolysis.
Reaction of alkyl halide with aqueous NaOH.
Hydroboration-oxidation of alkene.
Ozonolysis of alkene
Answer: (d)
Solution
Reacting a Grignard reagent with a ketone gives a tertiary alcohol. When alkyl halide reacts with aqueous sodium hydroxide to give alcohol, the reaction is called nucleophilic substitution. The Hydroboration Oxidation reaction is an organic chemical reaction which is employed for the conversion of alkenes into alcohols that are neutral. Reductive ozonolysis of alkenes will lead to formation of aldehyde or ketones, oxidative ozonolysis of alkenes will lead to formation of carboxylic acids or ketones. So, alcohol is not formed by ozonolysis of alkenes.
Question 62
Chemistry · Classification of Elements and Periodicity in Properties · Single correct
Given below are two statements: one is labelled as Assertion A and the other is labelled as Reason R. Assertion A: The energy required to form $\mathrm{Mg}^{2+}$ from $\mathrm{Mg}$ is much higher than that required to produce $\mathrm{Mg}^{+}$. Reason R: $\mathrm{Mg}^{2+}$ is small ion and carry more charge than $\mathrm{Mg}^{+}$. In the light of the above statements, choose the correct answer from the options given below.
Both A and R are true but R is NOT the correct explanation of A
A is true but R is false
A is false but R is true
Both A and R are true and R is the correct explanation of A
Answer: (d)
Solution
Mg have 2 electrons in valence shell and after donation of 2 electrons it converts into $\mathrm{Mg^{2+}}$ ion and attains inert gas configuration, now to ionize one more electron from inert gas configuration is very difficult, hence it is easy to ionize Mg to $\mathrm{Mg^{2+}}$. $\mathrm{IE_2}$ is always greater than $\mathrm{IE_1}$ because on removal of $e^-$, size decreases and effective nuclear charge increases. So Assertion is correct. $\mathrm{Mg^{2+}}$ is a smaller ion than $\mathrm{Mg^+}$ and has a greater charge density. This means that $\mathrm{Mg^{2+}}$ has a stronger attraction to its electrons than $\mathrm{Mg^+}$ and requires more energy to remove an electron from it. So reason is also correct.
Question 63
Chemistry · Organic Chemistry — Some Basic Principles & Techniques · Single correct
In Carius tube, an organic compound 'X' is treated with sodium peroxide to form a mineral acid 'Y'. The solution of $BaCl_2$ is added to 'Y' to form a precipitate 'Z'. 'Z' is used for the quantitative estimation of an extra element. 'X' could be
Cytosine
A nucleotide
Methionine
Chloroxylenol
Answer: (c)
Solution
Barium chloride is used to estimate sulphur content in the molecule. In Carius tube test, a known mass of sulphur present in an organic compound with Silver Nitrate is heated into a sealed tube known as Carius tube with silver. The organic compound is then converted to Sulphuric acid which then reacts with excess Barium Chloride solution and produces a precipitate of Barium Sulphate. $Z$ is $\mathrm{BaSO_4}$ and $Y$ is $\mathrm{H_2SO_4}$. It is clear that "X" must contain sulphur. Methionine is $\mathrm{C_5H_{11}NO_2S}$, a sulphur containing amino acid.
Question 64
Chemistry · Some Basic Concepts of Chemistry · Single correct
Given below are two statements: one is labelled as Assertion A and the other is labelled as Reason R. Assertion A: $3.1500 \, \mathrm{g}$ of hydrated oxalic acid dissolved in water to make $250.0 \, \mathrm{mL}$ solution will result in $0.1 \, \mathrm{M}$ oxalic acid solution. Reason R: Molar mass of hydrated oxalic acid is $126 \, \mathrm{g \, mol^{-1}}$. In the light of the above statements, choose the correct answer from the options given below:
Both A and R are true but R is NOT the correct explanation of A
A is true but R is false
Both A and R are true and R is the correct explanation of A
A is false but R is true
Answer: (c)
Solution
Molarity $\left( M \right) = \frac{wt}{mwt \times V} \times 1000$ Using this formula, we can calculate the molarity of the oxalic acid solution as follows: 1. Mass of hydrated oxalic acid $= 3.1500 \, \mathrm{g}$ 2. Molar mass of hydrated oxalic acid $(\mathrm{H_2C_2O_4 \cdot 2H_2O}) = 126.064 \, \mathrm{g/mol}$ 3. Volume of the solution $= 250.0 \, \mathrm{mL}$ Molarity $\left( M \right) = \frac{3.15 \times 1000}{126 \times 250} = 0.10$ So both assertion and reason are correct.
Question 65
Chemistry · Polymers · Single correct
Buna - S can be represented as:
Answer: (b)
Solution
Buna-S is a copolymer of 1,3-butadiene and styrene. It is prepared by copolymerisation of 1,3 butadiene and styrene along with sodium. In this process peroxide is used as a catalyst at $5^\circ \mathrm{C}$ therefore the formed product is also known as cold rubber. $$n \mathrm{CH_2} = \mathrm{HC} - \mathrm{CH} = \mathrm{CH_2} + n \rightarrow -(\mathrm{CH_2} - \mathrm{CH} = \mathrm{CH} - \mathrm{CH_2} - \mathrm{CH} - \mathrm{CH_2})_n$$
Question 66
Chemistry · Aldehydes, Ketones and Carboxylic Acids · Single correct
In the reaction given below The product 'X' is :
Answer: (c)
Solution
Lithium aluminium hydride, is a reducing agent that is commonly used in modern organic synthesis. It is a nucleophilic reducing agent that is best suited for reducing multiple polar bonds such as $\mathrm{C=O}$. It can reduce carbonyl compounds to alcohols and amides to amines. $\mathrm{C=C}$ is not effected during this reaction.
Question 67
Chemistry · Surface Chemistry · Single correct
Ferric chloride is applied to stop bleeding because
Blood absorbs $\mathrm{FeCl_3}$ and forms a complex.
$\mathrm{Cl^-}$ ions cause coagulation of blood.
$\mathrm{Fe^{3+}}$ ions coagulate blood which is a negatively charged sol.
$\mathrm{FeCl_3}$ reacts with the constituents of blood which is a positively charged sol.
Answer: (c)
Solution
Ferric chloride is a hemostatic agent, which means that it can be used to stop bleeding by promoting the coagulation of blood. Blood is a colloidal solution of an albuminoid substance and can be coagulated to form clot by applying $\mathrm{Fe^{3+}}$ ion on the open wound. Thus, bleeding caused by a razor during shaving can be treated by rubbing potash alum against the cut which helps in the coagulation of the blood by sealing the blood vessels.
Question 68
Chemistry · Chemistry in Everyday Life · Single correct
The reaction used for preparation of soap from fat is:
An addition reaction
Reduction reaction
Alkaline hydrolysis reaction
An oxidation reaction
Answer: (c)
Solution
The reaction used for preparation of soap from fat is not alkaline hydrolysis, but rather saponification. In saponification, a triglyceride (fat or oil) is reacted with a strong base, such as sodium hydroxide (or potassium hydroxide), in the presence of heat to produce soap molecules and glycerol as a byproduct. The reaction involves the hydrolysis of the ester bond in the triglyceride by the base to form carboxylate ions (the soap molecules) and glycerol.
Question 69
Chemistry · Organic Chemistry — Some Basic Principles & Techniques · Single correct
The decreasing order of hydride affinity for following carbocations is:
C, A, D, B
C, A, B, D
A, C, D, B
A, C, B, D
Answer: (b)
Solution
The stability of a carbocation increases with the number of alkyl groups attached to the carbon atom, due to the inductive and hyperconjugation effects of the alkyl groups. The more the number of alkyl groups, the greater is the electron density on the positively charged carbon, and hence the more stable is the carbocation. The above carbocation can be stabilised by resonance and hyperconjugation. The above carbocation stabilised by resonance caused by three benzene rings. This carbocation is more stable than the previous carbocation. The above carbocation stabilised by hyperconjugation. It is the least stable carbocation among the four carbocations given. The above carbocation is the most stable carbocation among the four due to the resonance caused by bent orbitals. From the given options Stability of carbocation: D > B > A > C The least stable carbocation will have the highest hydride affinity, because it is the most electron deficient and has the highest positive charge density. As a result, it will have the strongest attraction for a negatively charged hydride ion. Hydride affinity order: C > A > B > D
Question 70
Chemistry · The Solid State · Single correct
The correct relationships between unit cell edge length 'a' and radius of sphere 'r' for face-centred and body-centred cubic structures respectively are:
$2\sqrt{2}r = a$ and $\sqrt{3}r = 4a$
$r = 2\sqrt{2}a$ and $4r = \sqrt{3}a$
$r = 2\sqrt{2}a$ and $\sqrt{3}r = 4a$
$2\sqrt{2}r = a$ and $4r = \sqrt{3}a$
Answer: (d)
Solution
A face-centered cubic (fcc) unit cell contains a component in the center of each face in addition to those at the corners of the cube. The atoms touch each other along the face diagonal. For FCC: $a \sqrt{2} = 4r$ $$a = 2 \sqrt{2} r$$ A body-centered cubic (bcc) unit cell contains a component in the center of the cube in addition to those at the corners of the cube. The atoms touch each other along the body diagonal. For BCC: $a \sqrt{3} = 4r$
Question 71
Chemistry · The s-Block Elements · Single correct
Number of water molecules in washing soda and soda ash respectively are:
1 and 10
10 and 1
10 and 0
1 and 0
Answer: (c)
Solution
The chemical formula for washing soda is $\mathrm{Na_2 \, CO_3 \, 10H_2O}$, which means that each molecule of washing soda contains 10 water molecules. The chemical formula for soda ash is $\mathrm{Na_2 \, CO_3}$, which does not contain any water molecules. Therefore, there are 10 water molecules in washing soda and 0 water molecules in soda ash.
Question 72
Chemistry · Environmental Chemistry · Single correct
The delicate balance of $CO_2$ and $O_2$ is NOT disturbed by
Respiration
Burning of coal
Deforestation
Burning of petroleum
Answer: (a)
Solution
Plants use up carbon dioxide during photosynthesis and release oxygen into the atmosphere. This maintains the delicate balance between oxygen and carbon dioxide in the atmosphere. The burning of fuels and cutting of trees is disturbing this balance in nature. As a result of such activities, the amount of carbon dioxide in the air is going up and the level of oxygen is coming down. Continuous and excessive use of fuels and deforestation would increase this imbalance. This is bringing about a warming of the atmosphere, called global warming. Respiration, is a natural process, so balance of $\mathrm{CO_2}$ and $\mathrm{O_2}$ not disturbed by respiration.
Question 73
Chemistry · Co-ordination Compounds · Single correct
The correct order of the number of unpaired electrons in the given complexes is (A) $[\mathrm{Fe(CN)}_6]^{3-}$ (B) $[\mathrm{FeF}_6]^{3-}$ (C) $[\mathrm{CoF}_6]^{3-}$ (D) $[\mathrm{Cr(oxalate)}_3]^{3-}$ (E) $[\mathrm{Ni(CO)}_4]$ Choose the correct answer from the options given below:
E < A < D < C < B
E < A < B < D < C
A < E, C < B < D
A < E < D < C < B
Answer: (a)
Solution
The number of unpaired electrons in coordination complexes is determined by the nature of the central metal ion, the coordination number, and the identity and arrangement of the ligands around the metal ion. Based on these factors, the correct order of the number of unpaired electrons in the given complexes is: A $[\mathrm{Fe(CN)_6}]^{3-}$: $\mathrm{Fe^{3+}}$ $(3d^5)$ (Pairing of electrons takes place) $1$ B $[\mathrm{FeF_6}]^{3-}$: $\mathrm{Fe^{3+}}$ $(3d^5)$ $5$ C $[\mathrm{CoF_6}]^{3-}$: $\mathrm{Co^{3+}}$ $(3d^6)$ $4$ D $[\mathrm{Cr(oxalate)}_3]^{3-}$: $\mathrm{Cr^{3+}}$ $(3d^3)$ $3$ E $[\mathrm{Ni(CO)_4}]$: $\mathrm{Ni(3d^{10})}$ (Pairing of electrons takes place) $0$ No. of unpaired electrons order: E < A < D < C < B
Question 74
Chemistry · Organic Chemistry — Some Basic Principles & Techniques · Single correct
The correct order for acidity of the following hydroxyl compound is Choose the correct answer from the options given below: (A) $CH_3OH$ (B) $(CH_3)_3COH$
C > E > D > B > A
E > D > C > B > A
D > E > C > A > B
E > C > D > A > B
Answer: (d)
Solution
The compounds A & B are alcohols, and rest of the compounds are phenols. Phenols are more acidic than alcohols. Among the A & B, methyl alcohol is more acidic than tertiary butyl alcohol as alkyl groups decreases the acidic nature by electron releasing tendency. Among the phenols, the phenol with electron withdrawing group is more acidic. $\mathrm{NO_2}$ (Electron withdrawing group) group will increase the acidity, $\mathrm{OCH_3}$ (Electron releasing group) group at para position will decrease the acidity. So, Acidic strength $\mathrm{E > C > D > A > B}$
Question 75
Chemistry · Aldehydes, Ketones and Carboxylic Acids · Single correct
The major product ‘P’ formed in the given reaction is
Answer: (a)
Solution
Friedel-Crafts Alkylation refers to the replacement of an aromatic proton with an alkyl group. This is done through an electrophilic attack on the aromatic ring with the help of a carbocation generated from the alkyl halide and Lewis acid aluminium chloride. In the given case ring closure reaction takes place and $OCH_3$ is ortho/para directing, major product will be obtained from para attack.
Question 76
Chemistry · Analytical Chemistry · Single correct
Match List-I with List-II \begin{tabular}{|c|c|c|c|} \hline \textbf{List I} & \textbf{Complex} & \textbf{List II} & \textbf{Crystal Field Splitting Energy }($\Delta_o$) \\ \hline A. & $[\mathrm{Ti(H_2O)_6}]^{2+}$ & I. & $-1.2$ \\ \hline B. & $[\mathrm{V(H_2O)_6}]^{2+}$ & II. & $-0.6$ \\ \hline C. & $[\mathrm{Mn(H_2O)_6}]^{2+}$ & III. & $0$ \\ \hline D. & $[\mathrm{Fe(H_2O)_6}]^{3+}$ & IV. & $-0.8$ \\ \hline \end{tabular} Choose the correct answer from the options given below:
A-II, B-IV, C-I, D-III
A-IV, B-I, C-III, D-II
A-IV, B-I, C-II, D-III
A-II, B-IV, C-III, D-I
Answer: (c)
Solution
d-orbital is degenerate which split into two levels $e_g$ and $t_{2g}$ in the presence of ligands. This splitting is due to the presence of ligands. This is called the crystal-field splitting and the energy difference between the two levels is called the crystal-field splitting energy, $\Delta_0$. (A) $\mathrm{Ti^{2+} : 4s^03d^2}$ $t_{2g} \ e^- = 2$ $e_g \ e^- = 0$ $$\Delta_0 = 2(-.4\Delta_0) = -.8\Delta_0$$ (B) $\mathrm{V^{2+} : 4s^03d^3}$ $t_{2g} \ e^- = 3$ $e_g \ e^- = 0$ $$\Delta_0 = 3(-.4\Delta_0)$$ $$= -1.2\Delta_0$$ (C) $\mathrm{Mn^{3+} = 4s^03d^4}$ $t_{2g} \ e^- = 3$ $e_g \ e^- = 1$ $$\Delta_0 = 3(-.4\Delta_0) + 1(.6\Delta_0)$$ $$= -1.2\Delta_0 + 0.6\Delta_0$$ $$= -0.6\Delta_0$$ (D) $\mathrm{Fe^{3+} = 4s^03d^5}$ $t_{2g} \ e^- = 3$ $e_g \ e^- = 2$ $$\Delta_0 = 3(-.4\Delta_0) + 2(.6\Delta_0)$$ $$= -1.2\Delta_0 + 1.2\Delta_0 = 0$$
Question 77
Chemistry · Hydrogen · Single correct
Given below are two statements: one is labelled as Assertion A and the other is labelled as Reason R. Assertion A : Physical properties of isotopes of hydrogen are different. Reason R : Mass difference between isotopes of hydrogen is very large. In the light of the above statements, choose the correct answer from the options given below:
Both A and R are true and R is the correct explanation of A
A is false but R is true
A is true but R is false
Both A and R are true but R is NOT the correct explanation of A
Answer: (a)
Solution
The isotopes of hydrogen are protium, deuterium, and tritium, which have different physical properties. For example, deuterium has a higher boiling point and a lower vapor pressure than protium, while tritium is radioactive and has a much shorter half-life than the other two isotopes. The mass difference between the isotopes of hydrogen is indeed significant, with protium having a mass of 1 atomic mass unit (amu), deuterium having a mass of 2 amu, and tritium having a mass of 3 amu. So both A and R are true and R is the correct explanation of A.
Question 78
Chemistry · Some Basic Concepts of Chemistry · Single correct
Match List-I with List-II Choose the correct answer from the options given below:
A-II, B-III, C-IV, D-I
A-II, B-IV, C-I, D-III
A-I, B-III, C-II, D-IV
A-II, B-IV, C-III, D-I
Answer: (b)
Solution
The number of moles $= \frac{\text{Mass}}{\text{Molar mass}}$ The number of molecules $= \text{moles} \times N_A$ One mole of any gas occupies $22.7 \, \mathrm{L}$ at STP. $(A)$ Moles of $\mathrm{CH_4} = \frac{16}{16} = 1$ Molecules $= 6.02 \times 10^{23}$ Electrons $= 10 \times 6.02 \times 10^{23} = 60.2 \times 10^{23}$ $(B)$ Moles of $\mathrm{H_2} = \frac{1}{2} = 0.5$ mole Volume at STP $= \frac{1}{2} \times 22.7 = 11.35$ lit. $(C)$ $1$ mole $\mathrm{N_2} = 28$ gm $(D)$ $0.5$ mole $\mathrm{SO_2} = \frac{1}{2} \times 64 = 32$ gm
Question 79
Chemistry · Classification of Elements and Periodicity in Properties · Single correct
The correct order of metallic character is
K > $\mathrm{Be}$ > $\mathrm{Ca}$
$\mathrm{Be}$ > $\mathrm{Ca}$ > K
$\mathrm{Ca}$ > K > $\mathrm{Be}$
K > $\mathrm{Ca}$ > $\mathrm{Be}$
Answer: (d)
Solution
The metallic character of an element is defined as the easiness of its atom in losing electrons. According to the modern periodic table, the metallic character of an element decreases while moving from left to right across a period. K is an alkali metal. For alkaline earth metals, metallic character increases down the group. Hence, the correct order of metallic character is $\mathrm{K} > \mathrm{Ca} > \mathrm{Be}$.
Question 80
Chemistry · General Principles and Processes of Isolation of Elements · Single correct
Gibbs energy vs T plot for the formation of oxides is given below. For the given diagram, the correct statement is-
At $600^\circ \mathrm{C}, \mathrm{CO}$ cannot reduce \mathrm{FeO}
At $600^\circ \mathrm{C}, \mathrm{CO}$ can reduce $\mathrm{ZnO}$
At $600^\circ \mathrm{C}, \mathrm{C}$ can reduce $\mathrm{ZnO}$
At $600^\circ \mathrm{C}, \mathrm{C}$ can reduce $\mathrm{FeO}$
Answer: (d)
Solution
Ellingham diagrams are a particular graphical form of the principle that the thermodynamic feasibility of a reaction depends on the sign of $\Delta G$, the Gibbs free energy change, which is equal to $\Delta H - T \Delta S$, where $\Delta H$ is the enthalpy change and $\Delta S$ is the entropy change. Hence, element below in Ellingham diagram can reduce oxide of element above it. C can reduce FeO at $600 \, ^\circ \mathrm{C}$.
Question 81
Chemistry · Thermodynamics · Numerical
For the given reaction, if the initial pressure is $450 \, \mathrm{mmHg}$ and the pressure at time $t$ is $720 \, \mathrm{mmHg}$ at a constant temperature $T$ and constant volume $V$. The fraction of $\mathrm{A(g)}$ decomposed under these conditions is $x \times 10^{-1}$. The value of $x$ is (nearest integer)
In alkaline medium, the reduction of permanganate anion involves a gain of ___________ electrons.
Answer: 3
Solution
In faintly alkaline medium potassium permanganate changes to manganese dioxide in its oxidising action. $$\mathrm{MnO_4^- + 2H_2O + 3e^- \rightarrow MnO_2 + 4OH^-}$$ The oxidation state of manganese in $\mathrm{MnO_4^-}$ is $+7$ and in $\mathrm{MnO_2}$ is $+4$. Hence, it transfers 3 electrons during the oxidising action in alkaline medium.
Question 83
Chemistry · Thermodynamics · Fill in the blank
The number of endothermic processes from the following is _____. A. $\mathrm{I_2(g) \rightarrow 2I(g)}$ B. $\mathrm{HCl(g) \rightarrow H(g) + Cl(g)}$ C. $\mathrm{H_2O(l) \rightarrow H_2O(g)}$ D. $\mathrm{C(s) + O_2(g) \rightarrow CO_2(g)}$ E. Dissolution of ammonium chloride in water
$\mathrm{I_2(g) \rightarrow 2I(g)}$
$\mathrm{HCl(g) \rightarrow H(g) + Cl(g)}$
$\mathrm{H_2O(l) \rightarrow H_2O(g)}$
$\mathrm{C(s) + O_2(g) \rightarrow CO_2(g)}$
Dissolution of ammonium chloride in water
Answer: (d)
Solution
The decomposition reactions are endothermic reactions. The reactions $\mathrm{I_2(g) \rightarrow 2I(g)}$ and $\mathrm{HCl(g) \rightarrow H(g) + Cl(g)}$ are decomposition reactions. The heat vaporisation is an endothermic reaction. Hence, the conversion of $\mathrm{H_2O(l) \rightarrow H_2O(g)}$ is endothermic process. The heat of combustion is an exothermic process. The heat involved in $\mathrm{C(s) + O_2(g) \rightarrow CO_2(g)}$ is heat of combustion. The dissolution of ammonium chloride in water is an endothermic process. $\mathrm{NH_4Cl(s) \rightarrow NH_4^+(aq) + Cl^-(aq)}; \Delta H = +15.1 \, \mathrm{kJ/mol}.$
Question 84
Chemistry · Chemical Bonding and Molecular Structure · Numerical
The number of molecules from the following which contain only two lone pair of electrons is $H_2O$, $N_2$, $CO$, $XeF_4$, $NH_3$, $NO$, $CO_2$, $F_2$
Answer: 3
Solution
The lone pair of electrons can be identified by drawing structure of the given molecules as follows, $\mathrm{H_2O}$ has 2 lone pairs. $\mathrm{N_2}$ has 2 lone pairs. $\mathrm{CO}$ has 2 lone pairs. $\mathrm{XeF_4}$ has $2 + (4 \times 3) = 14$ lone pairs. $\mathrm{NH_3}$ has 1 lone pair. $\mathrm{NO}$ has 3 lone pairs. Reference for structure NCERT - XI pg 105 $\mathrm{CO_2}$ has 4 lone pairs. $\mathrm{F_2}$ has 6 lone pairs. The number of molecules having only 2 lone pair of electrons $= 3$ Which are $\mathrm{H_2O}$, $\mathrm{N_2}$ and $\mathrm{CO}$. $\mathrm{XeF_4}$ have 2 lone pairs on central atom, but we are asked about lone pair in molecule.
Question 85
Chemistry · The p-Block Elements (Group 15, 16, 17 & 18) · Numerical
The difference in the oxidation state of Xe between the oxidised product of $Xe$ formed on complete hydrolysis of $XeF_4$ and $XeF_4$ is
Answer: 2
Solution
Hydrolysis of $\mathrm{XeF_4}$ will give $\mathrm{XeO_3}$. This hydrolysis reaction is a redox reaction. This redox reaction is an example of disproportionation reaction. $$6\, \mathrm{XeF_4} + 12\, \mathrm{H_2O} \rightarrow 4\, \mathrm{Xe} + 2\, \mathrm{XeO_3} + 24\, \mathrm{HF} + 3\, \mathrm{O_2}$$ The oxidation states of Xenon in the reactant and product is $$\mathrm{XeO_3} : \mathrm{Xe}(+6)$$ $$\mathrm{XeF_4} : \mathrm{Xe}(+4)$$ Hence, the difference in oxidation state is 2.
Question 86
Chemistry · Solutions · Numerical
An aqueous solution of volume $300 \, \mathrm{cm}^3$ contains $0.63 \, \mathrm{g}$ of protein. The osmotic pressure of the solution at $300 \, \mathrm{K}$ is $1.29 \, \mathrm{mbar}$. The molar mass of the protein is $\mathrm{g} \, \mathrm{mol}^{-1}$. Given: $\mathbb{R} = 0.083 \, \mathrm{L_{bar}} K^{-1} mol^{-1}$
Answer: 40535
Solution
The osmotic pressure of a non-electrolytic solution can be calculated as follows, $$\pi = CRT$$ where $\pi$ is the osmotic pressure. $C$ is the molarity, given by $$C = \frac{Number of moles}{Volume of solution in L}$$ Calculating the molarity: $$1.29 \times 10^{-3} = \frac{0.63}{(\mathrm{MW})(0.3)} \times (0.083) \times 300$$ Solving for MW: $$\mathrm{MW} = \frac{0.63 \times 0.083 \times 300}{(0.3) \times (1.29 \times 10^{-3})}$$ This gives: $$= 40534.88$$ Rounding to the nearest integer: $$\approx 40535$$ (Nearest integer)
Question 87
Chemistry · Structure of Atom · Fill in the blank
For a metal ion, the calculated magnetic moment is $4.90 \, \mathrm{BM}$. This metal ion has $\_$$\_$$\_$$\_$$\_$ number of unpaired electrons
Answer: 4
Solution
The magnetic moment of the metal ion can be calculated using $$\mu = \sqrt{n(n+2)} \, BM$$ where $n$ is the number of unpaired electrons. Given $\mu = 4.90 \, BM$, $$4.90 \, BM = \sqrt{n(n+2)} \, BM$$ $$24 = n(n+2)$$ Solving for $n$, we find $$n = 4$$
Question 88
Chemistry · Structure of Atom · Numerical
The electron in the $n^{th}$ orbit of $\mathrm{Li}^{2+}$ is excited to $(n+1)$ orbit using the radiation of energy $1.47 \times 10^{-17} \, \mathrm{J}$ (as shown in the diagram). The value of $n$ is Given: $R_H = 2.18 \times 10^{-18} \, \mathrm{J}$
Answer: 1
Solution
The difference energy between two energy levels is $$\Delta E = 2.18 \times 10^{-18} \left[ \frac{1}{n_1^2} - \frac{1}{n_2^2} \right] \, \mathrm{J}$$ $$1.47 \times 10^{-17} = 2.18 \times 10^{-18} \times (9) \left( \frac{1}{(n)^2} - \frac{1}{(n+1)^2} \right)$$ $$0.749 = \frac{1}{n^2} - \frac{1}{(n+1)^2}$$ $$n = 1$$ Hence, the transition is taking place between $1 \rightarrow 2$, and it comes under Lyman series. If we take $0.749 \simeq 0.75 = \frac{3}{4}$
Question 89
Chemistry · Electrochemistry · Numerical
The specific conductance of 0.0025 M acetic acid is $5 \times 10^{-5} \mathrm{S \ cm}^{-1}$ at a certain temperature. The dissociation constant of acetic acid is _________ $\times 10^{-7}$. (Nearest integer) Consider limiting molar conductivity of $\mathrm{CH_3COOH}$ as $400 \mathrm{S \ cm}^2 \mathrm{mol}^{-1}$
Answer: 66
Solution
The relation between Molar conductance $\lambda_m$ and specific conductance $\kappa$ is $$\lambda_m = \frac{k \times 1000}{M}$$ $M$ = molarity $$\lambda_m = \frac{\left(5 \times 10^{-5}\right) \times \left(10^3\right)}{2.5 \times 10^{-3}} = 20 \, \mathrm{S \, cm^2 \, mol^{-1}}$$ Now, the degree of dissociation, $\alpha = \frac{\lambda_m}{\lambda_\infty}$ $$\alpha = \frac{20}{400} = \frac{1}{20}$$ The acid dissociation constant, $K_a = \frac{C \alpha^2}{(1-\alpha)} = \frac{\left(2.5 \times 10^{-3}\right) \left(\frac{1}{20} \times \frac{1}{20}\right)}{\left(\frac{19}{20}\right)}$$ $$= 65.789 \times 10^{-7}$$ $$\approx 66 \times 10^{-7}$$
Question 90
Chemistry · Chemical Kinetics and Nuclear Chemistry · Numerical
The number of incorrect statement/s from the following is _____________
The successive half lives of zero order reactions decreases with time.
A substance appearing as reactant in the chemical equation may not affect the rate of reaction
Order and molecularity of a chemical reaction can be a fractional number
The rate constant units of zero and second order reaction are $\mathrm{mol} \, \mathrm{L}^{-1} \, \mathrm{s}^{-1}$ and $\mathrm{mol}^{-1} \, \mathrm{L} \, \mathrm{s}^{-1}$ respectively
Answer: (a)
Solution
A. $C_0 \xrightarrow{t = \frac{2k}{C_0}} \frac{C_0}{2} \xrightarrow{t = \frac{4k}{C_0}} \frac{C_0}{4} \xrightarrow{t = \frac{8k}{C_0}} \frac{C_0}{8}$ Successive half lives of zero order reactions decreases with time. Note: successive half lives of first order reactions remains same. B. For zero order reactions, the rate of reaction is independent on the concentration of reactants. C. In some reaction molecularity (theoretical value) may be equal to the order of a reaction (experimental value). The order of a reaction may be fractional, zero, positive or negative. Molecularity can never be fractional. (D) Unit of $k = \frac{Units of rate}{[units of concentration]^{order}}$ Zero order $= mollit^{-1} sec^{-1}$ Second order $= mol^{-1} lit^{-1}$