JEE Main 24 January 2025 Shift 1 question paper with solutions
JEE Main 24 January 2025 Shift 1: all 75 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 · Vector Algebra · Single correct
Let $\vec{a} = \hat{i} + 2\hat{j} + 3\hat{k}$, $\vec{b} = 3\hat{i} + \hat{j} - \hat{k}$ and $\vec{c}$ be three vectors such that $\vec{c}$ is coplanar with $\vec{a}$ and $\vec{b}$. If the vector $\vec{c}$ is perpendicular to $\vec{b}$ and $\vec{a} \cdot \vec{c} = 5$, then $|\vec{c}|$ is equal to
$\sqrt{\frac{11}{6}}$
$\frac{1}{3\sqrt{2}}$
16
18
Answer: (a)
Solution
Given $\vec{c} = \lambda (\vec{b} \times (\vec{a} \times \vec{b}))$. This equals $\lambda ((\vec{b} \cdot \vec{b}) \vec{a} - (\vec{a} \cdot \vec{b}) \vec{b})$. Simplifying, we have $\lambda (11 \vec{a} - 2 \vec{b}) = \lambda (11i + 22j + 33k - 6i - 2j + 2k)$. This results in $\lambda (5i + 20j + 35k)$. Thus, $= 5\lambda (5i + 4j + 7k)$. Given $\vec{c} \cdot \vec{a} = 5$, we have $5\lambda (1 + 8 + 21) = 5$ which implies $\lambda = \frac{1}{30}$. Therefore, $\Rightarrow \vec{c} = \frac{1}{6} (i + 4j + 7k)$. The magnitude of $\vec{c}$ is $\vec{c} = \frac{\sqrt{1 + 16 + 49}}{6} = \frac{\sqrt{11}}{6}$.
Question 2
Maths · Integrals · Single correct
If $I(m,n) = \int_0^1 x^{m-1}(1-x)^{n-1} \, dx, m, n > 0$, then $I(9,14) + I(10,13)$ is
Let $f : \mathbb{R} - \{0\} \to \mathbb{R}$ be a function such that $f(x) - 6f\left(\frac{1}{x}\right) = \frac{35}{3x} - \frac{5}{2}$. If the $\lim_{x \to 0} \left(\frac{1}{\alpha x} + f(x)\right) = \beta; \alpha, \beta \in \mathbb{R}$, then $\alpha + 2\beta$ is equal to
Let $S_n = \frac{1}{2} + \frac{1}{6} + \frac{1}{12} + \frac{1}{20} + \ldots$ upto $n$ terms. If the sum of the first six terms of an A.P. with first term $-p$ and common difference $p$ is $\sqrt{2026} \ S_{2025}$, then the absolute difference between $20^{th}$ and $15^{th}$ terms of the A.P. is
Let $f(x) = \frac{2^{x+2} + 16}{2^{2x+1} + 2^{x+4} + 32}$. Then the value of $8 \left( f \left( \frac{1}{15} \right) + f \left( \frac{2}{15} \right) + \cdots + f \left( \frac{59}{15} \right) \right)$ is equal to
$\lim_{x \to 0} \operatorname{cosec}\, x \left(\sqrt{2\cos^2 x + 3\cos x} - \sqrt{\cos^2 x + \sin x + 4}\right)$ is:
0
$\frac{1}{\sqrt{15}}$
$\frac{1}{2\sqrt{5}}$
$-\frac{1}{2\sqrt{5}}$
Answer: (d)
Solution
Given the limit expression: $$ \lim_{x \to 0} \csc x \left( \sqrt{2 \cos^2 x + 3 \cos x - \sqrt{\cos^2 x + \sin x + 4}} \right) $$ We start by simplifying the expression inside the cosecant function: $$ \cos ec \, x \left( \cos^2 x + 3 \cos x - \sin x - 4 \right) $$ Taking the limit as $x$ approaches 0: $$ \lim_{x \to 0} \left( \sqrt{2 \cos^2 x + 3 \cos x + \sqrt{\cos^2 x + \sin x + 4}} \right) $$ Simplifying further: $$ \lim_{x \to 0} \frac{1}{\sin x} \left( \sqrt{2 \cos^2 x + 3 \cos x + \sqrt{\cos^2 x + \sin x + 4}} \right) $$ Using the identity $\sin x \approx x$ as $x \to 0$: $$ \lim_{x \to 0} \sin x \left( \sqrt{2 \cos^2 x + 3 \cos x + \sqrt{\cos^2 x + \sin x + 4}} \right) $$ Simplifying the expression: $$ \lim_{x \to 0} \sin x \left( \cos^x + 4 \right) (\cos x - 1) - \sin x $$ Further simplification gives: $$ \lim_{x \to 0} \sin x \left( \sqrt{2 \cos^2 x + 3 \cos x + \sqrt{\cos^2 x + \sin x + 4}} \right) $$ Simplifying the trigonometric terms: $$ -2 \sin^2 \frac{x}{2} (\cos x + 4) - 2 \sin \frac{x}{2} \cos \frac{x}{2} $$ Taking the limit: $$ \lim_{x \to 0} 2 \sin \frac{x}{2} \cos \frac{x}{2} \left( \sqrt{2 \cos^2 x + 3 \cos x + \sqrt{\cos^2 x + \sin x + 4}} \right) $$ Simplifying further: $$ - \left( \sin^x (\cos x + 4) + \cos \frac{x}{2} \right) $$ Finally, we have: $$ \lim_{x \to 0} \cos \frac{x}{2} \left( \sqrt{2 \cos^2 x + 3 \cos x + \sqrt{\cos^2 x + \sin x + 4}} \right) $$ The final result is: $$ - \frac{1}{2 \sqrt{5}} $$
Question 8
Maths · Three Dimensional Geometry · Single correct
Let in a $\triangle ABC$, the length of the side $AC$ be 6, the vertex $B$ be $(1, 2, 3)$ and the vertices $A, C$ lie on the line $\frac{x-6}{3} = \frac{y-7}{2} = \frac{z-7}{-2}$. Then the area (in sq. units) of $\triangle ABC$ is:
Let y = y(x) be the solution of the differential equation $\left( xy - 5x^2 \sqrt{1 + x^2} \right) dx + \left( 1 + x^2 \right) dy = 0, y(0) = 0.$ Then $y(\sqrt{3})$ is equal to
$\sqrt{\frac{15}{2}}$
$\frac{5\sqrt{3}}{2}$
$2\sqrt{2}$
$\sqrt{\frac{14}{3}}$
Answer: (b)
Solution
Given $\($(1 + x^2) $\frac{dy}{dx}$ + xy = 5x^2 $\sqrt{1 + x^2}$$\)$. Rewriting, we have $\($$\frac{dy}{dx}$ + $\frac{xy}{1 + x^2}$ = $\frac{5x^2}{\sqrt{1 + x^2}}$$\)$. The integrating factor is $\($$\mathrm{I.F.}$ = e^{$\int$ $\frac{x}{1+x^2}$ $\,$ dx} = e^{$\frac{\ln(1+x^2)}{2}$} = $\sqrt{1 + x^2}$$\)$. Thus, $\($y $\sqrt{1 + x^2}$ = $\int$ $\frac{5x^2}{\sqrt{1 + x^2}}$ $\cdot$ $\sqrt{1 + x^2}$ $\,$ dx$\)$. This simplifies to $\($y $\sqrt{1 + x^2}$ = $\int$ 5x^2 $\,$ dx$\)$. Integrating, we get $\($y $\sqrt{1 + x^2}$ = $\frac{5x^3}{3}$ + C$\)$. Given $\($y(0) = 0$\)$, we find $\($0 = 0 + C $\Rightarrow$ C = 0$\)$. Thus, $\($y = $\frac{5x^3}{3\sqrt{1 + x^2}}$$\)$. Finally, $\($y($\sqrt{3}$) = $\frac{15\sqrt{3}}{32}$ = $\frac{5\sqrt{3}}{2}$$\)$.
Question 10
Maths · Conic Sections · Single correct
Let the product of the focal distances of the point $\left(\sqrt{3},\frac{1}{2}\right)$ on the ellipse $\left(\frac{x^2}{a^2}+\frac{y^2}{b^2}=1,\ a>b\right)$, be $\frac{7}{4}$. Then the absolute difference of the eccentricities of two such ellipses is
A and B alternately throw a pair of dice. A wins if he throws a sum of 5 before B throws a sum of 8, and B wins if he throws a sum of 8 before A throws a sum of 5. The probability, that A wins if A makes the first throw, is
$\frac{8}{17}$
$\frac{9}{19}$
$\frac{9}{17}$
$\frac{8}{19}$
Answer: (b)
Solution
For sum '5' $\rightarrow$ (1,4), (2,3), (3,2) (4,1) $\Rightarrow$ P(A) = $\frac{4}{36}$ For sum '8' $\rightarrow$ (2,6), (3,5), (4,4) For sum '5' $\rightarrow$ (1,4), (2,3), (3,2) (4,1) $\Rightarrow$ P(A) = $\frac{4}{36}$ For sum '8' $\rightarrow$ (2,6), (3,5), (4,4) (5,3), (6,2) $\Rightarrow$ P(B) = $\frac{5}{36}$ $$P(\bar{A}) = \frac{32}{36}, P(\bar{B}) = \frac{31}{36}$$ $$P(A wins ) = P(A) + P(\bar{A})P(\bar{B})P(A) + P(\bar{A})P(\bar{B})P(\bar{A})P(\bar{B})P(A) + \ldots$$ $$= \frac{P(A)}{1 - P(\bar{A})P(\bar{B})} = \frac{9}{19}$$
Question 12
Maths · Applications of Integrals · Single correct
Consider the region $R = \{ (x, y) : x \leq y \leq 9 - \frac{11}{3} x^2, x \geq 0 \}$. The area, of the largest rectangle of sides parallel to the coordinate axes and inscribed in $R$, is:
$\frac{730}{119}$
$\frac{625}{111}$
$\frac{821}{123}$
$\frac{567}{121}$
Answer: (d)
Solution
Given the area function $A = 9t - t^2 - \frac{11}{3} t^3$. Differentiate with respect to $t$ to find $\frac{dA}{dt} = 9 - 2t - 11t^2$. Setting $\frac{dA}{dt} = 0$ gives $11t^2 + 2t - 9 = 0$. Solving this quadratic equation, $11t^2 + 11t - 9 = 0$ gives $t = \frac{-1 \pm \sqrt{81}}{11}$. The maximum occurs at $t = \frac{9}{11}$. Therefore, the largest area is $\frac{9}{11} \left( 9 - \frac{11}{3} \cdot \frac{81}{121} - \frac{9}{11} \right) = \frac{9}{11} \cdot \frac{63}{11} = \frac{567}{121}$.
Question 13
Maths · Applications of Integrals · Single correct
The area of the region $\{(x, y) : x^2 + 4x + 2 \leq y \leq |x + 2| \}$ is equal to
7
5
24/5
20/3
Answer: (d)
Solution
Given the inequality $x^2 + 4x + 2 \leq y \leq |x + 2|$. The required area $A_1$ is calculated as follows: $$A_1 = \int_{-4}^{0} \left[ 2 - (x^2 + 4x + 2) \right] \, dx - \frac{1}{2} \times 4 \times 2$$ Evaluating the integral: $$= \left( \frac{-x^3}{3} - 2x^2 \right)_{-4}^{0} - 4$$ $$= \left( 0 - \left( \frac{64}{3} - 32 \right) \right) - 4$$ $$= 32 - \frac{64}{3} - 4 = \frac{20}{3}$$
Question 14
Maths · Statistics · Single correct
For a statistical data $x_1, x_2, \ldots, x_{10}$ of 10 values, a student obtained the mean as 5.5 and $\sum_{i=1}^{10} x_i^2 = 371$. He later found that he had noted two values in the data incorrectly as 4 and 5, instead of the correct values 6 and 8, respectively. The variance of the corrected data is
Let circle $\mathcal{C}$ be the image of $x^2 + y^2 - 2x + 4y - 4 = 0$ in the line $2x - 3y + 5 = 0$ and $A$ be the point on $\mathcal{C}$ such that $OA$ is parallel to $x$-axis and $A$ lies on the right hand side of the centre $O$ of $\mathcal{C}$. If $B(\alpha, \beta)$ with $\beta < 4$ lies on $\mathcal{C}$ such that the length of the arc $AB$ is $(1/6)^{th}$ of the perimeter of $\mathcal{C}$$, then $$\beta$ - $\sqrt{3}$$\alpha$ is equal to
For some $n \neq 10$, let the coefficients of the $5$ th, $6$ th and $7$ th terms in the binomial expansion of $(1 + x)^{n+4}$ be in A.P. Then the largest coefficient in the expansion of $(1 + x)^{n+4}$ is:
20
10
35
70
Answer: (c)
Solution
Given $(1+x)^{n+4}$. $n+4C_4$, $n+4C_5$, $n+4C_6$ form an A.P. Therefore, $$2 \times n+4C_5 = n+4C_4 + n+4C_6$$ $$4 \times n+4C_5 = (n+4C_4 + n+4C_5) + (n+4C_5 + n+4C_6)$$ $$4 \times n+4C_5 = n+5C_5 + n+5C_6$$ $$\frac{4 \times 5! \cdot (n-1)!}{(n+4)!} = \frac{6! \cdot n!}{(n+6)!}$$ $$\Rightarrow 4 = \frac{(n+6)(n+5)}{6n}$$ $$\Rightarrow n^2 + 11n + 30 = 24n$$ $$\Rightarrow n^2 - 13n + 30 = 0$$ $$\Rightarrow n = 3, 10 (rejected)$$ Therefore, $n \neq 10$. Thus, the largest binomial coefficient in the expansion of $(1+x)^7$ (since $n+4 = 7$) is the coefficient of the middle term. Therefore, $$7C_4 = 7C_3 = 35$$
Question 17
Maths · Complex Numbers and Quadratic Equations · Single correct
The product of all the rational roots of the equation $(x^2 - 9x + 11)^2 - (x - 4)(x - 5) = 3$, is equal to
14
21
28
7
Answer: (a)
Solution
Given $\left( x^2 - 9x + 11 \right)^2 - (x-4)(x-5) = 3$. Let $x^2 - 9x + 11 = t$. Then, $t^2 - (t + 9) = 3$. This implies $t^2 - t - 12 = 0$. Further, $t^2 - 4t + 3t - 12 = 0$. Factoring gives $t(t - 4) + 3(t - 4) = 0$. Therefore, $t = 4$ or $-3$. For $x^2 - 9x + 11 = 4$, we have $x^2 - 9x + 7 = 0$. Here, we will get irrational roots. For $x^2 - 9x + 11 = -3$, we have $x^2 - 9x + 14 = 0$. Solving gives $x^2 - 7x - 2x + 14 = 0$, which implies $x = 7, 2$. Therefore, the product of all rational roots is $14$.
Question 18
Maths · Three Dimensional Geometry · Single correct
Let the line passing through the points $(-1, 2, 1)$ and parallel to the line $\frac{x-1}{2} = \frac{y+1}{3} = \frac{z}{4}$ intersect the line $\frac{x+2}{3} = \frac{y-3}{2} = \frac{z-4}{1}$ at the point $P$. Then the distance of $P$ from the point $Q(4, -5, 1)$ is
5
5$\sqrt{5}$
5$\sqrt{6}$
10
Answer: (b)
Solution
The equation of the line through the point $(-1, 2, 1)$ is given by $$\frac{x+1}{2} = \frac{y-2}{3} = \frac{z-1}{4} = \lambda.$$ So, $$x = 2\lambda - 1,$$ $$y = 3\lambda + 2,$$ $$z = 4\lambda + 1.$$ By equation (1), $$\frac{x+2}{3} = \frac{y-3}{2} = \frac{z-4}{1} = \mu (Let).$$ So, $$x = 3\mu - 2,$$ $$y = 2\mu + 3,$$ $$z = \mu + 4.$$ For the intersection point $P$, $$x = 2\lambda - 1 = 3\mu - 2,$$ $$y = 3\lambda + 2 = 2\mu + 3,$$ $$z = 4\lambda + 1 = \mu + 4.$$ So, point $P(x, y, z) = (1, 5, 5)$. Let $Q(4, -5, 1)$. Therefore, $$PQ = \sqrt{9 + 100 + 16} = \sqrt{125} = 5\sqrt{5}.$$
Question 19
Maths · Straight Lines and Pair of Straight Lines · Single correct
Let the lines $3x - 4y - \alpha = 0$, $8x - 11y - 33 = 0$, and $2x - 3y + \lambda = 0$ be concurrent. If the image of the point $(1, 2)$ in the line $2x - 3y + \lambda = 0$ is $\left( \frac{57}{13}, \frac{-40}{13} \right)$, then $|\alpha \lambda|$ is equal to
If the system of equations $$2x - y + z = 4$$ $$5x + \lambda y + 3z = 12$$ $$100x - 47y + \mu z = 212$$ has infinitely many solutions, then $\mu - 2\lambda$ is equal to
57
59
55
56
Answer: (a)
Solution
Given the equations: $$2x - y + z = 4$$ $$5x + \lambda y + 3z = 12$$ $$100x - 47y + \mu z = 212$$ We have $\Delta x = \Delta y = \Delta z = 0$. For $\Delta z$: $$\begin{vmatrix} 2 & -1 & 4 \\ 5 & \lambda & 12 \\ 100 & -47 & 212 \end{vmatrix} = 0$$ This implies: $$2(212\lambda + 564) + 1(1060 - 1200)$$ $$\Rightarrow 424\lambda + 1128 - 140 - 940 - 400\lambda = 0$$ $$\Rightarrow \lambda = -2$$ For $\Delta y$: $$\begin{vmatrix} 2 & -1 & 1 \\ 5 & -2 & 3 \\ 100 & -47 & \mu \end{vmatrix} = 0$$ This implies: $$2(-2\mu + 141) + 1(5\mu - 300) + 1(-235 + 200) = 0$$ $$\Rightarrow \mu = 53$$ Finally, $$\mu - 2\lambda = 53 - 2(-2) = 57$$
Question 21
Maths · Differential Equations · Numerical
Let $f$ be a differentiable function such that $2(x+2)^2 f(x) - 3(x+2)^2 = 10 \int_0^x (t+2) f(t) dt$, $x \geq 0$. Then $f(2)$ is equal to .
Maths · Inverse Trigonometric Functions · Fill in the blank
If for some $\alpha, \beta$; $\alpha \leq \beta$, $\alpha + \beta = 8$ and $\sec^2(\tan^{-1} \alpha) + \csc^2(\cot^{-1} \beta) = 36$, then $\alpha^2 + \beta$ is ______.
Answer: 14
Solution
Let $\tan^{-1} \alpha = A \Rightarrow \tan A = \alpha$. $\cot^{-1} \beta = B \Rightarrow \cot B = \beta$. $\sec^2 A + \csc^2 B = 36$. $$\Rightarrow 1 + \tan^2 A + 1 + \cot^2 B = 36$$ $$\Rightarrow \alpha^2 + \beta^2 = 34$$ Also $\alpha + \beta = 8$ (Given). Therefore, $(\alpha + \beta)^2 = 34 + 2\alpha\beta = 64$. $$\Rightarrow \alpha\beta = 15$$ Therefore, $\alpha, \beta$ are roots of the equation $$x^2 - 8x + 15 = 0$$ $$\Rightarrow (x - 3)(x - 5) = 0$$ $$\Rightarrow x = 3, 5$$ Therefore, $\alpha = 3, \beta = 5 (\alpha < \beta)$. Therefore, $\alpha^2 + \beta = 9 + 5 = 14$.
Question 23
Maths · Permutations and Combinations · Fill in the blank
The number of 3-digit numbers, that are divisible by 2 and 3, but not divisible by 4 and 9, is _____.
Answer: 125
Solution
No. of 3 digits = 999 - 99 = 900 No. of 3 digit numbers divisible by 2 & 3 i.e. by 6 $$\frac{900}{6} = 150$$ No. of 3 digit numbers divisible by 4 & 9 i.e. by 36 $$\frac{900}{36} = 25$$ Therefore, No. of 3 digit numbers divisible by 2 & 3 but not by 4 & 9 $$150 - 25 = 125$$
Question 24
Maths · Matrices · Numerical
Let $\mathbf{A}$ be a 3 $\times$ 3 matrix such that $X^{T}AX = 0$ for all nonzero 3 $\times$ 1 matrices $X = \begin{bmatrix} x \\ y \\ z \end{bmatrix}.$ If $\mathbf{A}$ $\begin{bmatrix} 1 \\ 1 \\ 1 \end{bmatrix}$ = $\begin{bmatrix} 1 \\ 4 \\ -5 \end{bmatrix}$, $\mathbf{A}$ $\begin{bmatrix} 1 \\ 2 \\ 1 \end{bmatrix}$ = $\begin{bmatrix} 0 \\ 4 \\ -8 \end{bmatrix}$, and $\det$(adj(2($\mathbf{A}$ + 1))) = $2^{\alpha}$ $3^{\beta}$ $5^{\gamma}$, $\alpha$, $\beta$, $\gamma$ $\in$ $\mathbb{N}$, then $\alpha^2$ + $\beta^2$ + $\gamma^2$ is $\underline{\hspace{1cm}}$
Answer: 44
Solution
Given $X^T A X = 0$. $\begin{pmatrix} x & y & z \end{pmatrix} \begin{pmatrix} a_1 & a_2 & a_3 \\ b_1 & b_2 & b_3 \\ c_1 & c_2 & c_3 \end{pmatrix} \begin{pmatrix} x \\ y \\ z \end{pmatrix} = 0$ $\begin{pmatrix} x & y & z \end{pmatrix} \begin{pmatrix} a_1 x + a_2 y + a_3 z \\ b_1 x + b_2 y + b_3 z \\ c_1 x + c_2 y + c_3 z \end{pmatrix} = 0$ $x (a_1 x + a_2 y + a_3 z) + y (b_1 x + b_2 y + b_3 z) + z (c_1 x + c_2 y + c_3 z)$ $a_1 = 0, b_2 = 0, c_3 = 0$ $a_2 + b_1 = 0, a_3 + c_1 = 0, b_3 + c_2 = 0$ $A = skew symmetric matrix$ $A = \begin{pmatrix} 0 & x & y \\ -x & 0 & z \\ -y & -z & 0 \end{pmatrix}; A \begin{pmatrix} 1 \\ 1 \\ 1 \end{pmatrix} = \begin{pmatrix} 1 \\ 4 \\ -5 \end{pmatrix}$ $\Rightarrow \begin{pmatrix} 0 & x & y \\ -x & 0 & z \\ -y & -z & 0 \end{pmatrix} \begin{pmatrix} 1 \\ 1 \\ 1 \end{pmatrix} = \begin{pmatrix} 1 \\ 4 \\ -5 \end{pmatrix}$ $x + y = 1$ $-x + z = 4$ $y + z = 5$ $\begin{pmatrix} 0 & x & y \\ -x & 0 & z \\ -y & -z & 0 \end{pmatrix} \begin{pmatrix} 1 \\ 2 \\ 1 \end{pmatrix} = \begin{pmatrix} 1 \\ 4 \\ -8 \end{pmatrix}$ $2x + y = 0 x = -1$ $-x + z = 4 y = 2$ $-y - 2z = -8 z = 3$ $A = \begin{pmatrix} 0 & -1 & 2 \\ 1 & 0 & 3 \\ -2 & -3 & 0 \end{pmatrix}$ $2(A + I) = \begin{pmatrix} 2 & -2 & 4 \\ 2 & 2 & 6 \\ -2 & -6 & 2 \end{pmatrix}$ $2(A + I) = 120$ $\Rightarrow \det(adj(2A + I)) = 120^2 = 2^6 \cdot 3^2 \cdot 5^2$ $\therefore \alpha = 6, \beta = 2, \gamma = 2$ Hence $\alpha^2 + \beta^2 + \gamma^2 = 6^2 + 2^2 + 2^2 = 44$
Question 25
Maths · Sets · Numerical
Let $S = \{p_1, p_2, \ldots, p_{10}\}$ be the set of first ten prime numbers. Let $A = S \cup P$, where $P$ is the set of all possible products of distinct elements of $S$. Then the number of all ordered pairs $(x, y)$, $x \in S$, $y \in A$, such that $x$ divides $y$, is ______.
Physics · Electrostatic Potential and Capacitance · Single correct
Consider a parallel plate capacitor of area A (of each plate) and separation 'd' between the plates. If $E$ is the electric field and $\varepsilon_0$ is the permittivity of free space between the plates, then potential energy stored in the capacitor is
$\varepsilon_0 E^2 A d$
$\frac{1}{2} \varepsilon_0 E^2 A d$
$\frac{1}{4} \varepsilon_0 E^2 A d$
$\frac{3}{4} \varepsilon_0 E^2 A d$
Answer: (b)
Solution
We know energy density $$\rho_{av} = \frac{1}{2} \varepsilon_0 E^2$$ So potential energy = $$\rho_{av} \times Volume$$ $$\Rightarrow P.E. = \frac{1}{2} \varepsilon_0 E^2 A d$$
Question 27
Physics · Ray Optics and Optical Instruments · Single correct
What is the relative decrease in focal length of a lens for an increase in optical power by 0.1 D from 2.5D ? ['D' stands for dioptre]
0.01
0.04
0.40
0.1
Answer: (b)
Solution
Initial optical power, $P_1 = 2.5 \, \mathrm{D}$ Final optical power, $P_2 = 2.5 \, \mathrm{D} + 0.1 \, \mathrm{D} = 2.6 \, \mathrm{D}$ Step 1: Relation Between Focal Length and Power The focal length $f$ (in meters) of a lens is related to its optical power $P$ by: $$P = \frac{1}{f}$$ So, $$f_1 = \frac{1}{P_1} = \frac{1}{2.5} = 0.4 \, \mathrm{m}$$ $$f_2 = \frac{1}{P_2} = \frac{1}{2.6} \approx 0.3846 \, \mathrm{m}$$ Step 2: Relative Decrease in Focal Length The relative decrease in focal length is given by: $$\frac{\Delta f}{f_1} = \frac{f_1 - f_2}{f_1}$$ Substituting the values: $$\Delta f = \frac{0.4 - 0.3846}{0.4}$$ $$= \frac{0.0154}{0.4}$$ $$= 0.0385 which is approx 0.04$$ Final Answer: 0.04
Question 28
Physics · Mechanical Properties of Fluids · Single correct
An air bubble of radius $0.1\,\text{cm}$ lies at a depth of $20\,\text{cm}$ below the free surface of a liquid of density $1000\,\text{kg m}^{-3}$. If the pressure inside the bubble is $2100\,\text{N m}^{-2}$ greater than the atmospheric pressure, then the surface tension of the liquid in SI units is ________. (Use $g = 10\,\text{m s}^{-2}$.)
Physics · Physical World, Units and Measurements · Single correct
For an experimental expression $y = \frac{32.3 \times 1125}{27.4}$, where all the digits are significant. Then to report the value of $y$ we should write
$y = 1326.19$
$y = 1330$
$y = 1326.186$
$y = 1326.2$
Answer: (b)
Solution
Given $\($ y = $\frac{32.3 \times 1125}{27.4}$ = 1326.18 $\)$. So we need to report to three significant digits. So, $\($ y = 1330 $\)$.
Question 30
Physics · Atoms · Single correct
During the transition of electron from state A to state C of a Bohr atom, the wavelength of emitted radiation is $2000\,Å$ and it becomes $6000\,Å$ when the electron jumps from state B to state C. Then the wavelength of the radiation emitted during the transition of electrons from state A to state B is
$4000\,Å$
$2000\,Å$
$3000\,Å$
$6000\,Å$
Answer: (c)
Solution
For A to C $$\frac{hc}{\lambda_1} = E_0 z^2 \left( \frac{1}{n_c^2} - \frac{1}{n_A^2} \right) \ldots (i)$$ And $$\frac{hc}{\lambda_2} = E_0 z^2 \left( \frac{1}{n_c^2} - \frac{1}{n_B^2} \right)$$ So for A and B $\ldots$ (ii) $$\frac{hc}{\lambda_3} = E_0 z^2 \left( \frac{1}{n_B^2} - \frac{1}{n_A^2} \right)$$ Clearly subtracting equation (ii) from equation (i) $$hc \left[ \frac{1}{\lambda_1} - \frac{1}{\lambda_2} \right] = E_0 z^2 \left[ \frac{1}{n_B^2} - \frac{1}{n_A^2} \right] = \frac{hc}{\lambda_3}$$ $$\Rightarrow \frac{1}{\lambda_3} = \frac{1}{\lambda_1} - \frac{1}{\lambda_2} \Rightarrow \frac{1}{\lambda_3} = \frac{(6000 - 2000)}{6000 \times 2000} = \frac{1}{3000}$$ $$\lambda_3 = 3000 \AA$$
Question 31
Physics · Semiconductor Electronics: Materials, Devices and Simple Circuits · Single correct
Consider the following statements: A. The junction area of solar cell is made very narrow compared to a photo diode. B. Solar cells are not connected with any external bias. C. LED is made of lightly doped p-n junction. D. Increase of forward current results in continuous increase of LED light intensity. E. LEDs have to be connected in forward bias for emission of light. Choose the correct answer from the options given below:
B, E Only
B, D, E Only
A, C Only
A, C, E Only
Answer: (a)
Solution
Clearly statement 'A' is wrong as for solar cell junction area are mode wide. LED connected in forward bias and its intensity increases up to certain value of current and further there is no change as intensity saturates. Also solar cells are not connected with any external bias.
Question 32
Physics · Mechanical Properties of Fluids · Single correct
The amount of work done to break a big water drop of radius $R$ into 27 small drops of equal radius is 10 J. The work done required to break the same big drop into 64 small drops of equal radius will be
Physics · System of Particles and Rotational Motion · Single correct
An object of mass 'm' is projected from origin in a vertical $xy$ plane at an angle $45^\circ$ with the $x$ axis with an initial velocity $v_0$. The magnitude and direction of the angular momentum of the object with respect to origin, when it reaches at the maximum height, will be [ $g$ is acceleration due to gravity]
$\frac{mv_0^3}{2\sqrt{2g}}$ along negative $z$-axis
$\frac{mv_0^3}{4\sqrt{2g}}$ along positive $z$-axis
$\frac{mv_0^3}{4\sqrt{2g}}$ along negative $z$-axis
$\frac{mv_0^3}{2\sqrt{2g}}$ along positive $z$-axis
Answer: (c)
Solution
Given the initial velocity $v_0$ at an angle of $45^\circ$, the maximum height $H$ is given by: $$H = \left( \frac{v_0}{\sqrt{2}} \right)^2 \frac{1}{2g} = \frac{v_0^2}{4g}.$$ The angular momentum $L$ is given by $L = mvh$. Substituting the values, we have: $$L = m \frac{v_0}{\sqrt{2}} \frac{v_0^2}{4g}.$$
Question 34
Physics · Wave Optics · Single correct
The Young's double slit interference experiment is performed using light consisting of 480 nm and 600 nm wavelengths to form interference patterns. The least number of the bright fringes of 480 nm light that are required for the first coincidence with the bright fringes formed by 600 nm light is
5
4
6
8
Answer: (a)
Solution
Given the equation $$\frac{n_1 \lambda_1 D}{d} = \frac{n_2 \lambda_2 D}{d}$$ and the conditions $$n_{480} = m_{600}$$ and $$n_{\min} = 5$$.
Question 35
Physics · Laws of Motion · Single correct
A car of mass ' m ' moves on a banked road having radius ' r ' and banking angle $\theta$. To avoid slipping from banked road, the maximum permissible speed of the car is $v_0$. The coefficient of friction $\mu$ between the wheels of the car and the banked road is
Physics · System of Particles and Rotational Motion · Single correct
A uniform solid cylinder of mass $m$ and radius $r$ rolls along a rough inclined plane of inclination $45^\circ$. If it starts rolling from rest from the top of the plane, then the linear acceleration of the cylinder's axis will be:
$\frac{1}{\sqrt{2}} g$
$\frac{1}{3\sqrt{2}} g$
$\frac{\sqrt{2} g}{3}$
$\sqrt{2} g$
Answer: (c)
Solution
For pure rolling about point $P$. $$\Rightarrow a = \frac{2g}{3} \sin \theta = \frac{2g}{3\sqrt{2}} = \frac{\sqrt{2}}{3} g$$
Question 37
Physics · Ray Optics and Optical Instruments · Single correct
A thin plano convex lens made of glass of refractive index 1.5 is immersed in a liquid of refractive index 1.2. When the plane side of the lens is silver coated for complete reflection, the lens immersed in the liquid behaves like a concave mirror of focal length 0.2 m. The radius of curvature of the curved surface of the lens is
$0.20\,\mathrm{m}$
$0.25\,\mathrm{m}$
$0.15\,\mathrm{m}$
$0.10\,\mathrm{m}$
Answer: (d)
Solution
Given the equation $$\frac{1.5}{v} = \frac{1.5 - 1.2}{R}$$ we have $$v = \frac{1.5R}{0.3} = 5R.$$ Then, $$\frac{1.2}{f} - \frac{1.5}{5R} = \frac{1.2 - 1.5}{-R}.$$ Simplifying, $$\frac{1.2}{f} = \frac{0.3}{R}.$$ Therefore, $$f \times 2 = f = 2R \Rightarrow R = 0.1.$$
Question 38
Physics · Oscillations · Single correct
A particle is executing simple harmonic motion with time period 2 s and amplitude 1 cm. If $D$ and $d$ are the total distance and displacement covered by the particle in 12.5 s, then $\frac{D}{d}$ is
A satellite is launched into a circular orbit of radius ' R ' around the earth. A second satellite is launched into an orbit of radius 1.03 R. The time period of revolution of the second satellite is larger than the first one approximately by
9$\%$
3$\%$
4.5$\%$
2.5$\%$
Answer: (c)
Solution
Given $T_1 \propto (R)^{3/2}$ and $T_2 \propto (1.03R)^{3/2}$. Therefore, $$T_2 = (1.03R)^{3/2} \cdot T_1 \approx 1.045T_1.$$ So $T_2$ will be larger by 4.5$\%$ with respect to $T_1$.
Question 40
Physics · Ray Optics and Optical Instruments · Single correct
A plano-convex lens having radius of curvature of first surface 2 cm exhibits focal length of $f_1$ in air. Another plano-convex lens with first surface radius of curvature 3 cm has focal length of $f_2$ when it is immersed in a liquid of refractive index 1.2. If both the lenses are made of same glass of refractive index 1.5, the ratio of $f_1$ and $f_2$ will be
1 : 2
1 : 3
3 : 5
2 : 3
Answer: (b)
Solution
Both lenses are plano-convex, so the second surface is plane ($R = \infty$), which simplifies the lens maker's formula: $$\frac{1}{f} = \left( n_n - 1 \right) \left( \frac{1}{R} - 0 \right)$$ where: - $n$ is the refractive index of the lens material, - $n_n$ is the refractive index of the surrounding medium, - $R$ is the radius of curvature of the curved surface. Step 1: Calculate $f_1$ (Lens in Air) For Lens 1 in Air: $$\frac{1}{f_1} = \left( \frac{1.5}{1} - 1 \right) \left( \frac{1}{2} \right)$$ $$\frac{1}{f_1} = (1.5 - 1) \times \frac{1}{2}$$ $$\frac{1}{f_1} = 0.5 \times \frac{1}{2} = \frac{0.5}{2} = \frac{1}{4}$$ $$f_1 = 4 \, \mathrm{cm}$$ Step 2: Calculate $f_2$ (Lens in Liquid) For Lens 2 in Liquid: $$\frac{1}{T_2} = \left( \frac{1.5}{1.2} - 1 \right) \left( \frac{1}{3} \right)$$ $$\frac{1}{T_2} = \left( \frac{1.5 - 1.2}{1.2} \right) \times \frac{1}{3}$$ $$\frac{1}{T_2} = \left( \frac{0.3}{1.2} \right) \times \frac{1}{3}$$ $$\frac{1}{T_2} = \frac{0.3}{3.6}$$ $$f_2 = \frac{3.6}{1.3} = 12 \, \mathrm{cm}$$ Step 3: Find the Ratio $\frac{4}{12}$ $$\frac{f_1}{f_2} = \frac{4}{12} = \frac{1}{3}$$ Final Answer: $$\frac{1}{3}$$
Question 41
Physics · Alternating Current · Single correct
An alternating current is given by $I = I_A \sin \omega t + I_B \cos \omega t$. The r.m.s current will be
$\frac{|I_A + I_B|}{\sqrt{2}}$
$\sqrt{\frac{I_A^2 + I_B^2}{2}}$
$\sqrt{I_A^2 + I_B^2}$
$\frac{\sqrt{I_A^2 + I_B^2}}{2}$
Answer: (b)
Solution
Given $i = i_1 \sin \omega t + i_2 \sin(\omega t + 90)$. We have $i = \sqrt{i_1^2 + i_2^2} \sin(\omega t + \phi)$. The rms current $i_{rms}$ is given by $$i_{rms} = \frac{i_0}{\sqrt{2}}$$ where $$i_0 = \sqrt{i_1^2 + i_2^2}$$ Thus, $$i_{rms} = \frac{\sqrt{i_1^2 + i_2^2}}{\sqrt{2}}$$
Question 42
Physics · Dual Nature of Radiation and Matter · Single correct
An electron of mass ' m ' with an initial velocity $\vec{v} = v_0 \hat{i} \,(v_0 > 0)$ enters an electric field $\vec{E} = -E_0 \hat{k}$. If the initial de Broglie wavelength is $\lambda_0$, the value after time $t$ would be
Given $\vec{v} = v_0 \hat{i} - \frac{E_0 e}{m} t \hat{k}$. The magnitude of $\vec{v}$ is given by $$|\vec{v}| = \sqrt{v_0^2 + \frac{E_0^2 e^2 t^2}{m^2}}.$$ The initial wavelength $\lambda_0$ is $$\lambda_0 = \frac{h}{mv_0}.$$ The new wavelength $\lambda'$ is $$\lambda' = \frac{h}{mv_0 \sqrt{1 + \frac{E_0^2 e^2 t^2}{v_0^2 m^2}}}.$$ Thus, $$\lambda' = \frac{\lambda_0}{\sqrt{1 + \frac{E_0^2 e^2 t^2}{v_0^2 m^2}}}.$$
Question 43
Physics · Electrostatic Potential and Capacitance · Single correct
A parallel plate capacitor was made with two rectangular plates, each with a length of $l = 3 \, \mathrm{cm}$ and breath of $b = 1 \, \mathrm{cm}$. The distance between the plates is $3 \, \mu \mathrm{m}$. Out of the following, which are the ways to increase the
A only
C only
B and D only
C and E only
Answer: (d)
Solution
We know $C = \frac{A \varepsilon_0}{d} = \frac{b \ell \varepsilon_0}{d}$. So to increase the capacitance by 10 factor $\left( \frac{A}{d} \right)$ has to increase by 10 factor. For option (A) $C' = \frac{(30 \ell) b \varepsilon_0}{\left( \frac{d}{3} \right)} = 30C$. For option (B) $C' = \frac{\ell b \varepsilon_0}{10d} = \frac{C}{10}$. For option (C) $C' = \frac{d}{(2 \ell) 5b \varepsilon_0} = 10C$. For option (D) $C' = \frac{\left( \frac{\ell}{3} \right) b \varepsilon_0}{\left( 10d \frac{3}{d} \right)} = \frac{C}{10}$. For option (E) $C' = \frac{\left( \frac{\ell}{3} \right) 5 (2b) \varepsilon_0}{\left( \frac{d}{3} \right)} = 10C$. Clearly (C) and (E) are the situation for 10C.
Question 44
Physics · Work, Energy and Power · Single correct
A force $\mathbf{F} = \alpha + \beta x^2$ acts on an object in the $x$-direction. The work done by the force is $5 \, \mathrm{J}$ when the object is displaced by $1 \, \mathrm{m}$. If the constant $\alpha = 1 \, \mathrm{N}$ then $\beta$ will be
$15 \, \mathrm{N/m^2}$
$12 \, \mathrm{N/m^2}$
$8 \, \mathrm{N/m^2}$
$10 \, \mathrm{N/m^2}$
Answer: (b)
Solution
Given $F = \alpha + \beta x^2$. Work done $\int dw = \int F \cdot dx$. Therefore, $$\Delta W = \int F \cdot dx = \int (\alpha + \beta x^2) \, dx$$ $$\Rightarrow \Delta W = \left| \alpha x + \frac{\beta x^3}{3} \right|_0^1 = \alpha + \frac{\beta}{3} = 5$$ Given $\alpha = 1$. So, $$\frac{\beta}{3} = 4$$ Therefore, $$\beta = 12 \, \mathrm{N/m^2}$$
Question 45
Physics · Kinetic Theory · Single correct
An ideal gas goes from an initial state to final state. During the process, the pressure of gas increases linearly with temperature. A. The work done by gas during the process is zero. B. The heat added to gas is different from change in its internal energy. C. The volume of the gas is increased. D. The internal energy of the gas is increased. E. The process is isochoric (constant volume process) Choose the correct answer from the options given below:
E Only
A, B, C, D Only
A, D, E Only
A, C Only
Answer: (c)
Solution
Given that $$P = kT$$ $$\frac{P}{T} = constant$$ Therefore, volume is constant or isochoric process. Thus, $W_D = 0$ and $Q = \Delta U$. Also, temperature increases hence internal energy increases.
Question 46
Physics · Electric Charges and Fields · Fill in the blank
A square loop of sides $a = 1 \, \mathrm{m}$ is held normally in front of a point charge $q = 1 \, \mathrm{C}$. The flux of the electric field through the shaded region is $\frac{5}{p} \times \frac{1}{\varepsilon_0} \, \mathrm{Nm^2/C}$, where the value of $p$ is .
Answer: 48
Solution
Total flux through square = $\frac{q}{\varepsilon_0} \left( \frac{1}{6} \right)$. Let's divide the square into 8 equal parts. Flux is the same for each part. Therefore, flux through shaded portion is $\frac{5}{8}$ (Total flux) $$= \frac{5}{8} \times \frac{q}{\varepsilon_0} \frac{1}{6} = \frac{5}{48} \frac{1}{\varepsilon_0}$$ Therefore, required answer is 48.
Question 47
Physics · Physical World, Units and Measurements · Numerical
The least count of a screw gauge is 0.01 mm. If the pitch is increased by 75$\%$ and number of divisions on the circular scale is reduced by 50$\%$, the new least count will be _____ $\times$ $10^{-3}$ $\mathrm{mm}$
A wire of resistance $9\,\Omega$ is bent to form an equilateral triangle. Then the equivalent resistance across any two vertices will be
Answer: 2
Solution
Given that $9\,\Omega$ is the resistance of the whole wire. Therefore, the resistance of each wire is $3\,\Omega$. Thus, the equivalent resistance is $2\,\Omega$.
Question 49
Physics · Moving Charges and Magnetism · Numerical
A current of 5A exists in a square loop of side $\frac{1}{\sqrt{2}}$ m. Then the magnitude of the magnetic field $B$ at the centre of the square loop will be $p \times 10^{-6}$ T. where, value of $p$ is _____. $Take \mu_0 = 4\pi \times 10^{-7} TmA^{-1}$.
Answer: 8
Solution
Let B be the magnetic field due to a single side. Then $B = \frac{\mu_0 i}{4 \pi \ d} (\sin \theta_1 + \sin \theta_2)$. $$= 10^{-7} \times 5 \times 2 \times \frac{1}{\sqrt{2}} = 2 \times 10^{-6}$$ Therefore, $B_{net}$ at centre $O = 4B$. $$= 8 \times 10^{-6}$$
Question 50
Physics · Kinetic Theory · Fill in the blank
The temperature of 1 mole of an ideal monoatomic gas is increased by $50^\circ \mathrm{C}$ at constant pressure. The total heat added and change in internal energy are $E_1$ and $E_2$, respectively. If $\frac{E_1}{E_2} = \frac{x}{9}$ then the value of $x$ is _____
Answer: 15
Solution
Given that process is isobaric $\Delta T = 50^\circ \mathrm{C}$. Q in isobaric process $= nC_p \Delta T = E_1$. $\Delta U$ in isobaric process $= nC_v \Delta T = E_2$. Therefore, $\frac{E_1}{E_2} = \frac{C_p}{C_v} = \gamma$. Given, gas is monoatomic. Therefore, $\gamma = 1 + \frac{2}{f} = 1 + \frac{2}{3} = \frac{5}{3}$. Now, as per question, $$\frac{5}{3} = \frac{x}{9}$$ $$x = 15$$
Chemistry
Question 51
Chemistry · Electrochemistry · Single correct
For the given cell $$\mathrm{Fe}^{2+}_{(aq)} + \mathrm{Ag}^+_{(aq)} \rightarrow \mathrm{Fe}^{3+}_{(aq)} + \mathrm{Ag}_{(s)}$$ The standard cell potential of the above reaction is Given: $$\mathrm{Ag}^+ + e^- \rightarrow \mathrm{Ag} E^\theta = x\,\mathrm{V}$$ $$\mathrm{Fe}^{2+} + 2e^- \rightarrow \mathrm{Fe} E^\theta = y\,\mathrm{V}$$ $$\mathrm{Fe}^{3+} + 3e^- \rightarrow \mathrm{Fe} E^\theta = z\,\mathrm{V}$$
$x + y - z$
$x + 2y$
$x + 2y - 3z$
$y - 2x$
Answer: (c)
Solution
Given the reaction $\mathrm{Fe^{2+}(aq) + Ag^+(aq) \rightarrow Fe^{3+}(aq) + Ag(s)}$. $$\Delta G_3^0 = \Delta G_1^0 + \Delta G_2^0$$ $$-3 \, F(-z) = -2 \, F(-y) + \Delta G_2^0$$ $$\Delta G_2^0 = 3Fz - 2Fy$$ Also, $$\Delta G_2^0 = -nF E^0_{\mathrm{Fe^{+2}/Fe^{t43}}}$$ $$3Fz - 2Fy = -1 \, F \left( E^0_{\mathrm{Fe^{+2}/Fe^{t43}}} \right)$$ $$E^0_{\mathrm{Fe^{+2}/Fe^{t3}}} = 2y - 3z$$ $E^0_{Cell}$ for reaction will be $$E^0_{\mathrm{Ag^+/Ag}} + E^{03}_{\mathrm{Fe^{t2}/Fe}}$$ $$= x + 2y - 3z$$
Question 52
Chemistry · Hydrocarbons · Single correct
Following are the four molecules "P", "Q", "R" and "S". Which one among the four molecules will react with H - $\mathrm{Br}_{(aq)}$ at the fastest rate?
R
P
Q
S
Answer: (c)
Solution
Addition of $\mathrm{H} - \mathrm{Br}_{(aq)}$ to alkene follows electrophilic addition mechanism. In the rate determining step a carbocation intermediate is formed. Among $\mathrm{P}$, $\mathrm{Q}$, $\mathrm{R}$ $\&$ $\mathrm{S}$ compound $\mathrm{Q}$ will form most stable carbocation intermediate since it is resonance stabilized.
Question 53
Chemistry · Co-ordination Compounds · Single correct
One mole of the octahedral complex compound $\mathrm{Co(NH_3)_5Cl_3}$ gives $3$ moles of ions on dissolution in water. One mole of the same complex reacts with an excess of $\mathrm{AgNO_3}$ solution to yield $2$ moles of $\mathrm{AgCl_{(s)}}$. The structure of the complex is:
The reaction is as follows: $$[\mathrm{Co(NH_3)_5Cl}] \mathrm{Cl_2} \rightarrow [\mathrm{Co(NH_3)_5Cl}]^{2+} \,(\mathrm{aq.}) + 2\mathrm{Cl}^- \,(\mathrm{aq.})$$ This results in 3 ions in water. The further reaction is: $$[\mathrm{Co(NH_3)_5Cl}] \mathrm{Cl_2} \,(\mathrm{aq.}) + 2\mathrm{AgNO_3} \,(\mathrm{aq.}) \rightarrow$$ $$[\mathrm{Co(NH_3)_5Cl}] \,(\mathrm{NO_3})_2 \,(\mathrm{aq.}) + 2\mathrm{AgCl(s)}$$
Question 54
Chemistry · Organic Chemistry — Some Basic Principles & Techniques · Single correct
Which one of the carbocations from the following is most stable?
Answer: (b)
Solution
The compound $\overset{+}{\mathrm{CH_2}}- \mathrm{CH=CH-O-CH_3}$ will be most stable due to extended conjugation. The compound (3) will be less stable due to the $-M$ effect of $\overset{-}{\mathrm{C}}=\mathrm{O}$.
Question 55
Chemistry · Chemical Bonding and Molecular Structure · Single correct
Which of the following linear combination of atomic orbitals will lead to formation of molecular orbitals in homonuclear diatomic molecules [internuclear axis in $z$-direction] ? A. $2p_z$ and $2p_x$ B. $2s$ and $2p_x$ C. $3d_{xy}$ and $3d_{x^2-y^2}$ D. $2s$ and $2p_z$ E. $2p_z$ and $3d_{x^2-y^2}$ Choose the correct answer from the options given below:
A and B Only
D Only
E Only
C and D Only
Answer: (b)
Solution
A: $p_x$ along $Z$ and $p_x$ along $X$ results in no molecular orbital. B: $s$ along $Z$ and $p_x$ along $X$ results in no molecular orbital. C: $d_{xy}$ along $Y$ and $d_{x^2-y^2}$ along $Y$ results in no molecular orbital. D: $s$ along $Z$ and $p_z$ along $Z$ results in a Sigma molecular orbital. E: $p_x$ along $Z$ and $d_{x^2-y^2}$ along $Y$ results in no molecular orbital.
Question 56
Chemistry · The d-and f-Block Elements · Single correct
Which of the following ions is the strongest oxidizing agent? (Atomic Number of Ce = 58, Eu = 63, Tb = 65, Lu = 71)
$Eu^{2+}$
$Tb^{4+}$
$Lu^{3+}$
$Ce^{3+}$
Answer: (b)
Solution
Tb^{4+} is the strongest oxidising agent as it will reduce to Tb^{3+} (common O.S. of Ln).
Question 57
Chemistry · Equilibrium · Single correct
$K_{sp}$ for $\mathrm{Cr(OH)_3}$ is $1.6 \times 10^{-30}$. What is the molar solubility of this salt in water?
$\frac{1.8 \times 10^{-30}}{27}$
$\sqrt[5]{1.8 \times 10^{-30}}$
$\sqrt[4]{\frac{1.6 \times 10^{-30}}{27}}$
$\sqrt[2]{1.6 \times 10^{-30}}$
Answer: (c)
Solution
The dissociation of $\mathrm{Cr(OH)_3}$ is given by: $$\mathrm{Cr(OH)_3 \rightleftharpoons Cr^{3+} (aq) + 3OH^- (aq)}$$ The solubility product is expressed as: $$K_{sp} = s(3s)^3$$ Simplifying, we have: $$1.6 \times 10^{-30} = 27s^4$$ Solving for $s$: $$\sqrt[4]{\frac{1.6 \times 10^{-30}}{27}} = s$$
Question 58
Chemistry · Thermodynamics · Single correct
Let us consider an endothermic reaction which is non-spontaneous at the freezing point of water. However, the reaction is spontaneous at boiling point of water. Choose the correct option.
Both $\Delta H$ and $\Delta S$ are (-ve)
$\Delta H$ is (-ve) but $\Delta S$ is (+ve)
$\Delta H$ is (+ve) but $\Delta S$ is (-ve)
Both $\Delta H$ and $\Delta S$ are (+ve)
Answer: (b)
Solution
On increasing temperature, the given endothermic reaction becomes spontaneous. $$\Delta G = \Delta H - T \Delta S$$ For spontaneity, $$\Delta G 0$$ So, $$\Delta S$$ should be positive.
Question 59
Chemistry · Organic Chemistry — Some Basic Principles & Techniques · Single correct
Given below are two statements I and II. Statement I: Dumas method is used for estimation of "Nitrogen" in an organic compound. Statement II: Dumas method involves the formation of ammonium sulphate by heating the organic compound with conc $\mathrm{H_2SO_4}$. In the light of the above statements, choose the correct answer from the options given below
Statement I is true but Statement II is false
Both Statement I and Statement II are false
Statement I is false but Statement II is true
Both Statement I and Statement II are true
Answer: (a)
Solution
In Dumas method nitrogen present in organic compound is converted into $\mathrm{N_2}$ gas whose volumetric analysis gives the percentage of nitrogen atom in the organic compound.
Question 60
Chemistry · Classification of Elements and Periodicity in Properties · Single correct
Which of the following statements are NOT true about the periodic table? A. The properties of elements are function of atomic weights. B. The properties of elements are function of atomic numbers. C. Elements having similar outer electronic configurations are arranged in same period. D. An element's location reflects the quantum numbers of the last filled orbital. E. The number of elements in a period is same as the number of atomic orbitals available in energy level that is being filled. Choose the correct answer from the options given below:
A, C and E Only
A and E Only
B, C and E Only
D and E Only
Answer: (a)
Solution
Properties of elements are function of atomic numbers. Elements having similar outer electronic configuration are arranged in same group. Number of elements in a period is double of number of atomic orbitals available in energy level that is being filled.
Question 61
Chemistry · Biomolecules · Single correct
The carbohydrate "Ribose" present in DNA, is A. A pentose sugar B. present in pyranose from C. in "D" configuration D. a reducing sugar, when free E. in $\alpha$-anomeric form Choose the correct answer from the options given below:
A, D and E Only
A, C and D Only
A, B and E Only
B, D and E Only
Answer: (b)
Solution
In Ribose carbohydrate present in DNA is $\beta - 2$-Deoxy-D-Ribose whose structure is which is a reducing $D$-sugar in $\beta$ anomeric form and it is a pentose sugar.
Question 62
Chemistry · The d-and f-Block Elements · Single correct
Preparation of potassium permanganate from $MnO_2$ involves two step process in which the 1st step is a reaction with KOH and $KNO_3$ to produce
$K_3MnO_4$
$K_4 [Mn(OH)_6]$
$KMnO_4$
$K_2MnO_4$
Answer: (d)
Solution
Preparation of $\mathrm{KMnO_4}$ $\mathrm{MnO_2} \xrightarrow[\mathrm{KNO_3}]{\mathrm{KOH}} K_2MnO_4 \xrightarrow[\text{Oxidation in alkaline solution}]{\text{Electrolysis}} KMnO_4$
Question 63
Chemistry · The p-Block Elements (Group 15, 16, 17 & 18) · Single correct
The large difference between the melting and boiling points of oxygen and sulphur may be explained on the basis of
Atomicity
Electron gain enthalpy
Electronegativity
Atomic size
Answer: (a)
Solution
The large difference in the melting and boiling points of oxygen and sulphur is due to atomicity as oxygen exists as $\mathrm{O_2}$ and sulphur exists as $\mathrm{S_8}$.
Question 64
Chemistry · Chemical Kinetics and Nuclear Chemistry · Single correct
For a reaction, $\mathrm{N_2O_5}_{(g)} \rightarrow 2\mathrm{NO_2}_{(g)} + \frac{1}{2}\mathrm{O_2}_{(g)}$ in a constant volume container, no products were present initially. The final pressure of the system when 50$\%$ of reaction gets completed is
5 times of initial pressure
5/2 times of initial pressure
7/2 times of initial pressure
7/4 times of initial pressure
Answer: (c)
Solution
The reaction is given by $\mathrm{N_2O_5}_{(g)} \rightarrow 2\mathrm{NO_2}_{(g)} + \frac{1}{2}\mathrm{O_2}_{(g)}$. At $t = 0$, the pressure is $P_0$. At time $t = t$, the pressure of $\mathrm{N_2O_5}$ is $P_0 - x$, the pressure of $\mathrm{NO_2}$ is $2x$, and the pressure of $\mathrm{O_2}$ is $\frac{x}{2}$. Solving for $x$, we have $x = \frac{P_0}{2}$. The total pressure $P_{total}$ is given by: $$P_{total} = P_0 - \frac{P_0}{2} + P_0 + \frac{P_0}{4} = \frac{7}{4} P_0$$
Question 65
Chemistry · Aldehydes, Ketones and Carboxylic Acids · Single correct
Which of the following arrangements with respect to their reactivity in nucleophilic addition reaction is correct?
Reactivity is proportional to the positive charge on electrophilic carbon. The correct order is I > II > III > IV.
Question 66
Chemistry · Aldehydes, Ketones and Carboxylic Acids · Single correct
Aman has been asked to synthesise the molecule (x). He thought of preparing the molecule using an aldol condensation reaction. He found a few cyclic alkenes in his laboratory. He thought of performing ozonolysis reaction on alkene to produce a dicarbonyl compound followed by aldol reaction to prepare "x". Predict the suitable alkene that can lead to the formation of "x".
Answer: (c)
Solution
Question 67
Chemistry · Solutions · Single correct
Consider the given plots of vapour pressure (VP) vs temperature (T/K). Which amongst the following options is correct graphical representation showing $\Delta T_f$, depression in the freezing point of a solvent in a solution?
Answer: (a)
Solution
On adding non-volatile solute in a solvent, the freezing point of solution decreases. $T_f < T_f^0$ F.P. of solution < F.P. of pure solvent. Also V.P. of solution decreases on adding nonvolatile solute in a solvent.
Question 68
Chemistry · Chemical Bonding and Molecular Structure · Multiple correct
Which of the following statement is true with respect to $\mathrm{H_2O}$, $\mathrm{NH_3}$ and $\mathrm{CH_4}$? A. The central atoms of all the molecules are $sp^3$ hybridized. B. The $\mathrm{H - O - H}$, $\mathrm{H - N - H}$ and $\mathrm{H - C - H}$ angles in the above molecules are $104.5^\circ$, $107.5^\circ$ and $109.5^\circ$, respectively. C. The increasing order of dipole moment is $\mathrm{CH_4} < \mathrm{NH_3} < \mathrm{H_2O}$. D. Both $\mathrm{H_2O}$ and $\mathrm{NH_3}$ are Lewis acids and $\mathrm{CH_4}$ is a Lewis base. E. A solution of $\mathrm{NH_3}$ in $\mathrm{H_2O}$ is basic. In this solution $\mathrm{NH_3}$ and $\mathrm{H_2O}$ act as Lowry-Bronsted acid and base respectively. Choose the correct answer from the options given below:
A, B and C Only
A, D and E Only
C, D and E Only
A, B, C and E Only
Answer: (a)
Solution
Dipole moment $\mathrm{H_2O} > \mathrm{NH_3} > \mathrm{CH_4}$. $\mathrm{H_2O}$ and $\mathrm{NH_3}$ are Lewis Bases. $\mathrm{NH_3}$ acts as a Lowry-Bronsted base. Hence, A, B & C are correct.
Question 69
Chemistry · Haloalkanes and Haloarenes · Single correct
Given below are two statements: Statement I: The conversion proceeds well in the less polar medium. $CH_3-CH_2-CH_2-CH_2-Cl \xrightarrow{HO^-} CH_3-CH_2-CH_2-CH_2-OH+Cl^{-}$ Statement II: The conversion proceeds well in the more polar medium. In the light of the above statements, choose the correct answer from the options given below
Both Statement I and Statement II are true
Statement I is true but Statement II is false
Statement I is false but Statement II is true
Both Statement I and Statement II are false
Answer: (a)
Solution
Question 70
Chemistry · Aldehydes, Ketones and Carboxylic Acids · Single correct
The product (A) formed in the following reaction sequence is
Answer: (b)
Solution
Question 71
Chemistry · Equilibrium · Numerical
37.8 g $\mathrm{N}_2\mathrm{O}_5$ was taken in a 1 L reaction vessel and allowed to undergo the following reaction at 500 K ${2}{\mathrm{N_2O_2}}_{(g)} \rightleftharpoons {2}{\mathrm{N_2O_4}}_{(g)} + {\mathrm{O_2}}_{(g)}$ The total pressure at equilibrium was found to be 18.65 bar. Then, $K_p = \underline{\hspace{1cm}} \times 10^{-2}$ [nearest integer] Assume $\mathrm{N}_2\mathrm{O}_5$ to behave ideally under these conditions. Given: $R = 0.082 \, \mathrm{bar} \, \mathrm{L} \mathrm{mol}^{-1} \, \mathrm{K}^{-1}$
Answer: 74
Solution
Initial pressure of $\mathrm{N_2O_5}$ is calculated as follows: $$\frac{37.8}{108} \times 0.082 \times 500 = 14.35 \, bar$$ The reaction is: $$2 \, \mathrm{N_2O_5} \rightleftharpoons 2 \, \mathrm{N_2O_4} + \mathrm{O_2}$$ At $t = 0$, the pressure is $14.35$. At equilibrium, $t = eq$, the pressures are $14.35 - 2P$ and $2P$. The total pressure at equilibrium is $\mathrm{P_{Total}} = 14.35 + P = 18.65$. Solving for $P$, we get $P = 4.3$. The partial pressures are: $$\mathrm{P_{N_2O_5}} = 5.75 \, bar$$ $$\mathrm{P_{N_2O_4}} = 8.6 \, bar$$ $$\mathrm{P_{O_2}} = 4.3 \, bar$$ The equilibrium constant $k_p$ is calculated as: $$k_p = \frac{(8.6)^2 \times (4.3)}{(5.75)^2} = 9.619 = x \times 10^{-2}$$ Thus, $x = 961.9 \approx 962$.
Question 72
Chemistry · Thermodynamics · Numerical
Standard entropies of $X_2$, $Y_2$ and $XY_5$ are $70$, $50$ and $110 \, \mathrm{J} \, \mathrm{K}^{-1} \, \mathrm{mol}^{-1}$ respectively. The temperature in Kelvin at which the reaction $$\frac{1}{2}X_2 + \frac{5}{2}Y_2 \rightleftharpoons XY_5 \Delta H^\Theta = -35 \, \mathrm{kJ} \, \mathrm{mol}^{-1}$$ will be at equilibrium is ______. (Nearest integer)
Answer: 3
Solution
For the reaction $\frac{1}{2} X_2 + \frac{5}{2} Y_2 \rightarrow XY_5$, the change in entropy $\Delta S^0_{Rxn}$ is calculated as follows: $$\Delta S^0_{Rxn} = 110 - \left[ \left( \frac{1}{2} \times 70 \right) + \left( \frac{5}{2} \times 50 \right) \right]$$ This simplifies to: $$= 110 - 160 = -50 \, \mathrm{JK^{-1} \, mol^{-1}}$$ At equilibrium, $\Delta G^0 = 0$. Therefore, $$\Delta G^0 = \Delta H^0 - T \Delta S^0$$ Substituting the values: $$0 = -35000 - T(-50)$$ Solving for $T$ gives: $$T = 700 \, Kelvin$$
Question 73
Chemistry · Aldehydes, Ketones and Carboxylic Acids · Numerical
X g of benzoic acid on reaction with aq $\mathrm{NaHCO_3}$ released $\mathrm{CO_2}$ that occupied $11.2 \, \mathrm{L}$ volume at STP. X is ______ g.
Answer: 61
Solution
1 mole benzoic acid will release 1 mole $\mathrm{CO_2}$. 11.2 L $\mathrm{CO_2}$ at STP is $\frac{1}{2}$ mole $\mathrm{CO_2}$, which will be released by reaction with $\frac{1}{2}$ mole benzoic acid. Mass of benzoic acid $= \frac{1}{2} \times 122 = 61 \, \mathrm{gm}$.
Question 74
Chemistry · Analytical Chemistry · Numerical
Among the following cations, the number of cations which will give characteristic precipitate in their identification tests with $K_4[Fe(CN)_6]$ is _____. $Cu^{2+}$, $Fe^{3+}$, $Ba^{2+}$, $Ca^{2+}$, $NH_4^+$, $Mg^{2+}$, $Zn^{2+}$
Answer: 4
Solution
Only $\mathrm{Cu^{2+}}$, $\mathrm{Fe^{3+}}$, $\mathrm{Ca^{2+}}$ and $\mathrm{Zn^{2+}}$ form precipitate with $\mathrm{K_4[Fe(CN)_6]}$.
Question 75
Chemistry · General Principles and Processes of Isolation of Elements · Numerical
Consider the following reaction occurring in the blast furnace: $$\mathrm{Fe_3O_4}_{(s)} + 4\mathrm{CO}_{(g)} \rightarrow 3\mathrm{Fe}_{(l)} + 4\mathrm{CO_2}_{(g)}$$ 'x' kg of iron is produced when $2.32 \times 10^3$ kg $\mathrm{Fe_3O_4}$ and $2.8 \times 10^2$ kg $\mathrm{CO}$ are brought together in the furnace. The value of 'x' is _____. (nearest integer) Given: molar mass of $\mathrm{Fe_3O_4} = 232 \, \mathrm{g \, mol^{-1}}$ molar mass of $\mathrm{CO} = 28 \, \mathrm{g \, mol^{-1}}$ molar mass of $\mathrm{Fe} = 56 \, \mathrm{g \, mol^{-1}}$