JEE Main 29 July 2022 Shift 2 question paper with solutions
JEE Main 29 July 2022 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 · Complex Numbers and Quadratic Equations · Single correct
If $z \neq 0$ be a complex number such that $\left| z - \frac{1}{z} \right| = 2$, then the maximum value of $|z|$ is:
$\sqrt{2}$
1
$\sqrt{2} - 1$
$\sqrt{2} + 1$
Answer: (d)
Solution
Given $|z - \frac{1}{z}| = 2$. Let $|z| = r$. We have: $$\left| z - \frac{1}{|z|} \right| \leq |z - \frac{1}{z}| \leq |z| + \frac{1}{|z|}$$ This implies: $$\left| r - \frac{1}{r} \right| \leq 2 \leq r + \frac{1}{r}$$ This is always true. Therefore: $$r - \frac{1}{r} \geq -2 and r - \frac{1}{r} \leq 2$$ Solving these inequalities: $$r^2 - 1 \leq 2r$$ $$r^2 - 2r \leq 1$$ $$(r - 1)^2 \leq 2$$ $$r - 1 \leq \sqrt{2}$$ Thus, $|z|_{\max} = 1 + \sqrt{2}$.
Question 2
Maths · Matrices · Single correct
Which of the following matrices can NOT be obtained from the matrix $$\begin{bmatrix} -1 & 2 \\ 1 & -1 \end{bmatrix}$$ by a single elementary row operation?
If the system of equations $x + y + z = 6$ $2x + 5y + \alpha z = \beta$ $x + 2y + 3z = 14$ has infinitely many solutions, then $\alpha + \beta$ is equal to :
8
36
44
48
Answer: (c)
Solution
Given the equations: $$x + y + z = 6 (1)$$ $$2x + 5y + \alpha z = \beta (2)$$ $$x + 2y + 3z = 14 (3)$$ From equation (1), we have $$x + y = 6 - z$$ From equation (3), we have $$x + 2y = 14 - 3z$$ On solving, $$x = z - 2 \implies y = 8 - 2z in (2)$$ Substitute in equation (2): $$2(z - 2) + 5(8 - 2z) + \alpha z = \beta$$ Simplifying, $$(\alpha - 8)z = \beta - 36$$ For having infinite solutions, $$\alpha - 8 = 0 \& \beta - 36 = 0$$ Thus, $$\alpha = 8, \beta = 36 (\alpha + \beta = 44)$$
Question 4
Maths · Continuity and Differentiability · Single correct
Let the function $$f(x) = \begin{cases} \frac{\log_e (1 + 5x) - \log_e (1 + \alpha x)}{x} & ; if x \neq 0 \\ 10 & ; if x = 0 \end{cases}$$ be continuous at $x = 0$. The $\alpha$ is equal to:
10
-10
5
-5
Answer: (d)
Solution
Given $$f(x) = \begin{cases} \frac{\ln(1+5x) - \ln(1+\alpha x)}{x} & ; x \neq 0 \\ 10 & ; x = 0 \end{cases}$$ We find $$\lim_{x \to 0} \frac{\ln(1+5x) - \ln(1+\alpha x)}{x} = 10$$ Using expansion, $$\lim_{x \to 0} \frac{(5x + \ldots) - (\alpha x + \ldots)}{x} = 10$$ This gives $$5 - \alpha = 10 \implies \alpha = -5$$
Question 5
Maths · Integrals · Single correct
If [t] denotes the greatest integer $\leq t$, then the value of $$\int_0^1 \left[ 2x - |3x^2 - 5x + 2| + 1 \right] \, dx$$ is:
Let $\{a_n\}_{n=0}^{\infty}$ be a sequence such that $a_0 = a_1 = 0$ and $$ a_{n+2} = 3a_{n+1} - 2a_{n+1}, \forall n \geq 0. $$ Then $a_{25} a_{23} - 2 a_{25} a_{22} - 2 a_{23} a_{24} + 4 a_{22} a_{24}$ is equal to:
If the solution curve of the differential equation $\($ $\frac{dy}{dx}$ = $\frac{x+y-2}{x-y}$ $\)$ passes through the point $\($(2,1)$\)$ and $\($(k+1,2)$\)$, $\($k > 0$\)$, then
\[ \frac{dy}{dx} = \frac{x+y-2}{x-y} = \frac{(x-1)+(y-1)}{(x-1)-(y-1)} \] \[ x - 1 = X, \quad y - 1 = Y \] \[ \frac{dY}{dX} = \frac{X+Y}{X-Y} \] \[ Y = VX \qquad \frac{dY}{dX} = V + X\frac{dV}{dX} \] \[ V + X\frac{dV}{dX} = \frac{1+V}{1-V} \qquad X\frac{dV}{dX} = \frac{V^2+1}{1-V} \] \[ \int \frac{1-V}{1+V^2}\,dV = \int \frac{dX}{X} \] \[ \int \frac{dV}{1+V^2} - \frac{1}{2}\int \frac{2V\,dV}{1+V^2} = \int \frac{dX}{X} \] \[ \tan^{-1}V - \frac{1}{2}\ln\left(1+V^2\right) = \ln X + c \] \[ \tan^{-1}\left(\frac{Y}{X}\right) - \frac{1}{2}\ln\left(1+\frac{Y^2}{X^2}\right) = \ln(X) + c \] \[ \tan^{-1}\left(\frac{y-1}{x-1}\right) - \frac{1}{2}\ln\left(1+\frac{(y-1)^2}{(x-1)^2}\right) = \ln(x-1) + c \] Passes through $(2,1)$ \[ 0 - \frac{1}{2}\ln 1 = \ln 1 + c \quad \therefore c = 0 \] Passes through $(k+1, 2)$ \[ \therefore \tan^{-1}\left(\frac{1}{k}\right) - \frac{1}{2}\ln\left(1+\frac{1}{k^2}\right) = \ln k \] \[ \Rightarrow 2\tan^{-1}\left(\frac{1}{k}\right) = \log_e\left(k^2+1\right) \]
Question 10
Maths · Differential Equations · Single correct
Let $y = y (x)$ be the solution curve of the differential equation $\frac{dy}{dx} + \left( \frac{2x^2 + 11x + 13}{x^3 + 6x^2 + 11x + 6} \right)$ $y = \left( \frac{x+3}{x+1} \right), x > -1$, which passes through the point $(0,1)$. Then $y (1)$ is equal to:
Maths · Straight Lines and Pair of Straight Lines · Single correct
Let $m_1, m_2$ be the slopes of two adjacent sides of a square of side $a$ such that $a^2 + 11a + 3(m_2^2 + m_1^2) = 220$. If one vertex of the square is $(10(\cos \alpha - \sin \alpha), 10(\sin \alpha + \cos \alpha))$, where $\alpha \in \left(0, \frac{\pi}{2}\right)$ and the equation of one diagonal is $(\cos \alpha - \sin \alpha) x + (\sin \alpha + \cos \alpha) y = 10$, then $72(\sin^4 \alpha + \cos^4 \alpha) + a^2 - 3a + 13$ is equal to:
The number of elements in the set $$S = \left\{ x \in \mathbb{R} : 2 \cos \left( \frac{x^2 + x}{6} \right) = 4^x + 4^{-x} \right\}$$ is:
1
3
0
infinite
Answer: (a)
Solution
Given $$2 \cos \left( \frac{x^2 + x}{6} \right) = 4^x + 4^{-x}$$ L.H.S $\leq$ 2 and R.H.S $\geq$ 2. Hence L.H.S = 2 and R.H.S = 2. $$2 \cos \left( \frac{x^2 + x}{6} \right) = 2 4^x + 4^{-x} = 2$$ Check $x = 0$. Possible, hence only one solution.
Question 13
Maths · Properties of Triangles · Single correct
Let A ($\alpha$, $-2$), B ($\alpha$, 6) and C $\left( \frac{\alpha}{4}, -2 \right)$ be vertices of a $\triangle ABC$. If $\left( 5, \frac{\alpha}{4} \right)$ is the circumcentre of $\triangle ABC$, then which of the following is NOT correct about $\triangle ABC$:
area is 24
perimeter is 25
circumradius is 5
inradius is 2
Answer: (b)
Solution
$A(\alpha, -2)$, $B(\alpha, 6)$, $C\left(\dfrac{\alpha}{4}, -2\right)$ Since $AC$ is perpendicular to $AB$, $\triangle ABC$ is right angled at $A$. Circumcentre $=$ midpoint of $BC = \left(\dfrac{5\alpha}{8},\ 2\right)$ $$\therefore\ \frac{5\alpha}{8} = 5 \quad \text{and} \quad \frac{\alpha}{4} = 2$$ $\alpha = 8$ $$B = (8, 6)$$ $\text{Area} = \dfrac{1}{2}(6)(8) = 24$ $\text{Perimeter} = 24$ $\text{Circumradius} = 5$ $\text{Inradius} = \dfrac{\Delta}{s} = \dfrac{24}{12} = 2$
Question 14
Maths · Three Dimensional Geometry · Single correct
Let Q be the foot of perpendicular drawn from the point P (1, 2, 3) to the plane x + 2y + z = 14. If R is a point on the plane such that $\angle PRQ = 60^\circ$, then the area of $\triangle PQR$ is equal to:
$\frac{\sqrt{3}}{2}$
$\sqrt{3}$
$2\sqrt{3}$
3
Answer: (b)
Solution
Length of perpendicular $$PQ = \frac{|1 + 4 + 3 - 14|}{\sqrt{6}} = \sqrt{6}$$ $$QR = (PQ) \cot 60^\circ = \sqrt{2}$$ Therefore, the area of $\triangle PQR = \frac{1}{2} (PQ)(QR) = \sqrt{3}$
Question 15
Maths · Vector Algebra · Single correct
If $(2, 3, 9)$, $(5, 2, 1)$, $(1, \lambda, 8)$ and $(\lambda, 2, 3)$ are coplanar, then the product of all possible values of $\lambda$ is:
$\frac{21}{2}$
$\frac{59}{8}$
$\frac{57}{8}$
$\frac{95}{8}$
Answer: (d)
Solution
Given points A(2, 3, 9), B(5, 2, 1), C(1, $\lambda$, 8), and D($\lambda$, 2, 3). The condition is that the vectors $\overrightarrow{AB}$, $\overrightarrow{AC}$, and $\overrightarrow{AD}$ are coplanar, which implies: $$\begin{vmatrix} 3 & -1 & -8 \\ -1 & \lambda - 3 & -1 \\ \lambda - 2 & -1 & -6 \end{vmatrix} = 0$$ Expanding the determinant, we have: $$[-6(\lambda - 3) - 1] - 8(1 - (\lambda - 3)(\lambda - 2)) + (6 + (\lambda - 2)) = 0$$ Simplifying, we get: $$3(-6\lambda + 17) - 8(-\lambda^2 + 5\lambda - 5) + (\lambda + 4) = 8$$ This simplifies to: $$8\lambda^2 - 57\lambda + 95 = 0$$ The product of the roots is given by: $$\lambda_1 \lambda_2 = \frac{95}{8}$$
Question 16
Maths · Probability · Single correct
Bag I contains 3 red, 4 black and 3 white balls and Bag II contains 2 red, 5 black and 2 white balls. One ball is transferred from Bag I to Bag II and then a ball is draw from Bag II. The ball so drawn is found to be black in colour. Then the probability, that the transferred ball is red, is:
$\frac{4}{9}$
$\frac{5}{18}$
$\frac{1}{6}$
$\frac{3}{10}$
Answer: (b)
Solution
Given: A: Drown ball from boy II is black B: Red ball transferred The probability is given by: $$ \mathrm{P} \left( \frac{B}{A} \right) = \frac{\mathrm{P}(A \cap B)}{\mathrm{P}(A)} $$ Calculating: $$ = \frac{\frac{3}{9} \times \frac{5}{10}}{\frac{3}{9} \times \frac{5}{10} + \frac{4}{9} \times \frac{6}{10} + \frac{3}{9} \times \frac{5}{10}} $$ Simplifying: $$ = \frac{15}{15 + 24 + 15} = \frac{15}{54} = \frac{5}{18} $$
Question 17
Maths · Complex Numbers and Quadratic Equations · Single correct
Let $S = \{ z = x + iy : |z - 1 + i| \geq |z|, |z| < 2, |z + i| = |z - 1| \}$. Then the set of all values of $x$, for which $w = 2x + iy \in S$ for some $y \in \mathbb{R}$, is
Let $\vec{a}$, $\vec{b}$, $\vec{c}$ be three coplanar concurrent vectors such that angles between any two of them is same. If the product of their magnitudes is 14 and $$(\vec{a} \times \vec{b}) \cdot (\vec{b} \times \vec{c}) + (\vec{b} \times \vec{c}) \cdot (\vec{c} \times \vec{a}) + (\vec{c} \times \vec{a}) \cdot (\vec{a} \times \vec{b}) = 168$$ then $|\vec{a}| + |\vec{b}| + |\vec{c}|$ is equal to:
The statement $(p \Rightarrow q) \lor (p \Rightarrow r)$ is NOT equivalent to:
$(p \land (\sim r)) \Rightarrow q$
$(\sim q) \Rightarrow ((\sim r) \lor p)$
$p \Rightarrow (q \lor r)$
$(p \land (\sim q)) \Rightarrow r$
Answer: (b)
Solution
(p $\rightarrow$ q) $\lor$ (p $\rightarrow$ r) ($\sim$ p $\lor$ q) $\lor$ ($\sim$ p $\lor$ r) = $\sim$ p $\lor$ (q $\lor$ r) = p $\rightarrow$ (q $\lor$ r) $\equiv$ (3) is true. Now (1) (p $\land$ $\sim$ r) $\rightarrow$ q $\sim$ (p $\land$ $\sim$ r) $\lor$ q = ($\sim$ p $\lor$ r) $\lor$ q = $\sim$ p $\lor$ (r $\lor$ q) = p $\rightarrow$ (q $\lor$ r) (4) (p $\land$ $\sim$ q) $\rightarrow$ r = p $\rightarrow$ (q $\lor$ r)
Question 21
Maths · Probability · Numerical
The sum and product of the mean and variance of a binomial distribution are 82.5 and 1350 respectively. They the number of trials in the binomial distribution is:
Answer: 96
Solution
Let, mean = m = np and variance = v = npq, p + q = 1. Sum = m + v = $\frac{165}{2}$. Product = mv = 1350. On solving, m = np = 60 and v = npq = $\frac{45}{2}$. Therefore, q = $\frac{3}{8}$ and P = $\frac{5}{8}$. Hence n = 96.
Question 22
Maths · Complex Numbers and Quadratic Equations · Numerical
Let $\alpha$, $\beta$ ($\alpha > \beta$) be the roots of the quadratic equation $x^2 - x - 4 = 0$. If $P_n = \alpha^n - \beta^n$, $n \in \mathbb{N}$, then $$\frac{P_{15}P_{16} - P_{14}P_{16} - P_{15}^2 + P_{14}P_{15}}{P_{13}P_{14}}$$ is equal to .
The number of natural numbers lying between $1012$ and $23421$ that can be formed using the digits $2,3,4,5,6$ (repetition of digits is not allowed) and divisible by $55$ is ______.
Answer: 6
Solution
4 digit numbers For divisibility by 55, the number should be divisible by 5 and 11 both. Also, for divisibility by 11: $$a + c = b + 5$$ For $b = 1$: $a = 2$, $c = 4$ $a = 4$, $c = 2$ For $b = 2$: $a = 3$, $c = 4$ $a = 4$, $c = 3$ For $b = 3$: $a = 6$, $c = 2$ $a = 2$, $c = 6$ Therefore, 6 possible four digit numbers are divisible by 55. (II) 5 digit number is not possible. (Not possible)
Question 25
Maths · Binomial Theorem · Fill in the blank
If\[ \sum_{k=1}^{10} k^2\left({}^{10}C_k\right)^2=22000L, \] then $L$ is equal to \_\_\_\_.
Answer: 221
Solution
Given $$\sum_{K=1}^{10} K^2 \left( \binom{10}{K} \right)^2$$ This is equal to $$\sum_{K=1}^{10} \left( K \cdot \binom{10}{K} \right)^2 = \sum_{K=1}^{10} \left( 10 \cdot \binom{9}{K-1} \right)^2$$ This simplifies to $$= 100 \sum_{K=1}^{10} \binom{9}{K-1} \cdot \binom{9}{10-K}$$ Which is equal to $$= 100 \binom{18}{9} = 100 \left( \frac{18!}{9!9!} \right)$$ Thus, $$\Rightarrow 4862000 = 22000L$$ Hence, $$L = 221$$
Question 26
Maths · Continuity and Differentiability · Numerical
If [t] denotes the greatest integer $\leq t$, then number of points, at which the function $f(x) = 4 \lvert 2x + 3 \rvert + 9 \left[ x + \frac{1}{2} \right] - 12 \left[ x + 20 \right]$ is not differentiable in the open interval $(-20, 20)$, is ___.
Answer: 79
Solution
Given $f(x) = 4|2x + 3| + 9\left[x + \frac{1}{2}\right] - 12[x + 20]$. $x \in (-20, 20)$. $f(x)$ is not differentiable at $x = I \in \{-19, -18, \ldots, 0, \ldots, 19\} = 39$ points. At $x = I + \frac{1}{2}$, $f(x)$ is non-differentiable at 39 points. Check at $x = \frac{-3}{2}$. Discount at $x = \frac{-3}{2}$. Therefore, $N. R(1)$. Number of points of non-differentiability: $$= 39 + 39 + 1 = 79$$
Question 27
Maths · Applications of Derivatives · Numerical
If the tangent to the curve $y = x^3 - x^2 + x$ at the point $(a, b)$ is also tangent to the curve $y = 5x^2 + 2x - 25$ at the point $(2, -1)$, then $|2a + 9b|$ is equal to .
Answer: 195
Solution
Given $y = x^3 - x^2 + x$. At point $P(2, -1)$, the derivative $\frac{dy}{dx}$ is $22$. Therefore, the tangent to the curve at $P$ is given by: $$y + 1 = 22(x - 2)$$ Simplifying, we get: $$y = 22x - 45$$ For the curve $y = x^3 - x^2 + x$, the derivative is: $$\frac{dy}{dx} \bigg|_{C_2} = 3x^2 - 2x + 1$$ At point $Q(a, b)$, the derivative is: $$\frac{dy}{dx} \bigg|_Q = 3a^2 - 2a + 1$$ Setting this equal to $22$, we have: $$3a^2 - 2a + 1 = 22$$ Simplifying, we get: $$3a^2 - 2a - 21 = 0$$ Factoring, we find: $$3a^2 - 9a + 7a - 21 = 0$$ Solving, we find $a = 3$ and $b = 21$. The equation $2a + 9b = 195$ is satisfied. At $a = -7/3$, the tangent will be parallel, hence it is rejected.
Question 28
Maths · Conic Sections · Numerical
Let AB be a chord of length 12 of the circle $$(x - 2)^2 + (y + 1)^2 = \frac{169}{4}.$$ If tangents drawn to the circle at points A and B intersect at the point P, then five times the distance of point P from chord AB is equal to ___.
Answer: 72
Solution
Given the diagram, we have: $$\cos \theta = \frac{6}{\frac{13}{2}} = \frac{12}{13}$$ $$\sin \theta = \frac{5}{13}$$ The relation for PM is given by: $$\mathrm{PM} = \mathrm{AM} \cot \theta$$ Substituting the values, we get: $$\mathrm{PM} = 6 \left( \frac{12}{5} \right) \therefore 5(\mathrm{PM}) = 72$$
Question 29
Maths · Vector Algebra · Numerical
Let $\vec{a}$ and $\vec{b}$ be two vectors such that $|\vec{a} + \vec{b}|^2 = |\vec{a}|^2 + 2 |\vec{b}|^2$, $\vec{a} \cdot \vec{b} = 3$ and $|\vec{a} \times \vec{b}|^2 = 75$. Then $|\vec{a}|^2$ is equal to ____.
Let $$S = \left\{ (x, y) \in \mathbb{N} \times \mathbb{N} : 9(x-3)^2 + 16(y-4)^2 \leq 144 \right\}$$ and $$T = \left\{ (x, y) \in \mathbb{R} \times \mathbb{R} : (x-7)^2 + (y-4)^2 \leq 36 \right\}.$$ The $n(S \cap T)$ is equal to ____.
Answer: 27
Solution
Given the set S: $\($ $\frac{(x-3)^2}{16}$ + $\frac{(y-4)^2}{9}$ $\leq$ 1 $\)$; $\($ x, y $\in$ $\{$1, 2, 3, $\ldots$$\}$ $\)$. Set T: $\($ (x-7)^2 + (y-4)^2 $\leq$ 36 $\)$; $\($ x, y $\in$ $\mathbb{R}$ $\)$. Let $\($ x-3 = x : y-4 = y $\)$. The set S: $\($ $\frac{x^2}{16}$ + $\frac{y^2}{9}$ $\leq$ 1 $\)$; $\($ x $\in$ $\{$-2, -1, 0, 1, $\ldots$$\}$ $\)$. The set T: $\($ (x-4)^2 + y^2 $\leq$ 36 $\)$; $\($ y $\in$ $\{$-3, -2, -1, 0, $\ldots$$\}$ $\)$. The intersection $\($ S $\cap$ T = (-2, 0), (-1, 0), $\ldots$, (4, 0) $\rightarrow$ (7) $\)$. $\($(-1, 1), (0, 1), $\ldots$, (3, 1) $\rightarrow$ (5) $\)$. $\($(-1, -1), (0, -1), $\ldots$, (3, -1) $\rightarrow$ (5) $\)$. $\($(-1, 2), (0, 2), (1, 2), (2, 2) $\rightarrow$ (4) $\)$. $\($(-1, -2), (0, -2), (1, -2), (2, -2) $\rightarrow$ (4) $\)$. $\($(0, 3) (0, -3) $\rightarrow$ (2) $\)$.
Physics
Question 31
Physics · Electric Charges and Fields · Single correct
Two identical metallic spheres A and B when placed at certain distance in air repel each other with a force of F. Another identical uncharged sphere C is first placed in contact with A and then in contact with B and finally placed at midpoint between spheres A and B. The force experienced by sphere C will be:
3F/2
3F/4
F
2F
Answer: (b)
Solution
Let $q_A = q_B = q$. $$F = \frac{Kq^2}{r^2}$$ When C is placed in contact with A, charge on A and C will be $\frac{q}{2}$. Now C is placed in contact with B, charge on B and C will be $\frac{q + \frac{q}{2}}{2} = \frac{3q}{4}$. Now, $$\frac{q}{2} \overset{F_1}{\longleftarrow} A \overset{F_2}{\longrightarrow} C \overset{F_2}{\longrightarrow} B \frac{3q}{4}$$ $$F' = F_2 - F_1 = \left( \frac{K \frac{3q}{4} - K \frac{q}{2}}{\frac{r^2}{4}} \right) \cdot \frac{3q}{4}$$ $$= \frac{3Kq^2}{4r^2} = \frac{3F}{4} (B)$$
Question 32
Physics · Physical World, Units and Measurements · Single correct
Match List I with List II. Choose the correct answer from the options given below:
A-III, B-II, C-I, D-IV
A-III, B-IV, C-II, D-I
A-IV, B-I, C-III, D-II
A-II, B-III, C-I, D-IV
Answer: (b)
Solution
Torque is given by $Torque = F \times r_\perp$ and is measured in Nm. Stress is given by $Stress = \frac{Force}{Area}$ and is measured in N/m$^2$. Latent heat is given by $Latent heat = \frac{Energy}{Mass}$ and is measured in J Kg$^{-1}$. Power is given by $Power = \frac{Work}{Time}$ and is measured in N ms$^{-1}$. The correct matching is A-III, B-IV, C-II, D-I.
Question 33
Physics · Electrostatic Potential and Capacitance · Single correct
Two identical thin metal plates has charge $q_1$ and $q_2$ respectively such that $q_1 > q_2$. The plates were brought close to each other to form a parallel plate capacitor of capacitance $C$. The potential difference between them is :
$\frac{(q_1 + q_2)}{C}$
$\frac{(q_1 - q_2)}{C}$
$\frac{(q_1 - q_2)}{2C}$
$\frac{2(q_1 - q_2)}{C}$
Answer: (c)
Solution
Electric field between plates is given by $E = \frac{q_1 - q_2}{2A \epsilon_0}$. The potential $V$ is given by $V = Ed = \frac{q_1 - q_2}{2A \epsilon_0} d$. Thus, $V = \frac{q_1 - q_2}{2C}$.
Question 34
Physics · Current Electricity · Single correct
Given below are two statements: one is labelled as Assertion A and the other is labelled as Reason R. Assertion A: Alloys such as constantan and manganin are used in making standard resistance coils. Reason R: Constantan and manganin have very small value of temperature coefficient of resistance. 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.
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.
Answer: (a)
Solution
Theory based
Question 35
Physics · Current Electricity · Single correct
A 1 m long wire is broken into two unequal parts X and Y. The X part of the wire is stretched into another wire W. Length of W is twice the length of X and the resistance of W is twice that of Y. Find the ratio of length of X and Y.
1 : 4
1 : 2
4 : 1
2 : 1
Answer: (b)
Solution
Given $\($ $\frac{R_X}{R_Y}$ = $\frac{\ell_X}{\ell_Y}$ $\)$. When wire is stretched to double of its length, then resistance becomes 4 times. $\($ R_W = 4R_X = 2R_Y $\)$. $\($ $\frac{R_X}{R_Y}$ = $\frac{1}{2}$ $\)$. So, $\($ $\frac{\ell_X}{\ell_Y}$ = $\frac{1}{2}$ $\)$.
Question 36
Physics · Moving Charges and Magnetism · Single correct
A wire X of length 50 cm carrying a current of 2 A is placed parallel to a long wire Y of length 5 m. The wire Y carries a current of 3 A. The distance between two wires is 5 cm and currents flow in the same direction. The force acting on the wire Y is :
$1.2 \times 10^{-5}\,\mathrm{N}$ directed towards wire X.
$1.2 \times 10^{-4}\,\mathrm{N}$ directed away from wire X.
$1.2 \times 10^{-4}\,\mathrm{N}$ directed towards wire X.
$2.4 \times 10^{-5}\,\mathrm{N}$ directed towards wire X.
Physics · Motion in a Straight Line · Single correct
A juggler throws balls vertically upwards with same initial velocity in air. When the first ball reaches its highest position, he throws the next ball. Assuming the juggler throws n balls per second, the maximum height the balls can reach is
$\frac{g}{2n}$
$\frac{g}{n}$
$2gn$
$\frac{g}{2n^2}$
Answer: (d)
Solution
Time taken by ball to reach highest point is $\frac{u}{g}$. Frequency of throw is $\frac{g}{u} = n$. Therefore, $u = \frac{g}{n}$. The maximum height $H_{max}$ is given by $$H_{max} = \frac{u^2}{2g} = \frac{\left(\frac{g}{n}\right)^2}{2g}$$ which simplifies to $$\frac{g}{2n^2}.$$
Question 38
Physics · Alternating Current · Single correct
A circuit element X when connected to an a.c. supply of peak voltage 100 V gives a peak current of 5 A which is in phase with the voltage. A second element Y when connected to the same a.c. supply also gives the same value of peak current which lags behind the voltage by $\frac{\pi}{2}$. If X and Y are connected in series to the same supply, what will be the rms value of the current in ampere?
$\frac{10}{\sqrt{2}}$
$\frac{5}{\sqrt{2}}$
$5\sqrt{2}$
$\frac{5}{2}$
Answer: (d)
Solution
Element X should be resistive with $R = 20 \, \Omega$. Element Y should be inductive with $X_L = 20 \, \Omega$. When X and Y are connected in series, $$Z = \sqrt{X_L^2 + R^2} = 20 \sqrt{2}$$ $$I_0 = \frac{E_0}{Z} = \frac{100}{20 \sqrt{2}} = \frac{5}{\sqrt{2}} \, \mathrm{A}$$ $$I_{\mathrm{rms}} = \frac{I_0}{\sqrt{2}} = \frac{5}{2} \, \mathrm{A}$$
Question 39
Physics · Wave Optics · Single correct
An unpolarised light beam of intensity $2I_0$ is passed through a polaroid P and then through another polaroid Q which is oriented in such a way that its passing axis makes an angle of $30^\circ$ relative to that of P. The intensity of the emergent light is
Physics · Dual Nature of Radiation and Matter · Single correct
An $\alpha$ particle and a proton are accelerated from rest through the same potential difference. The ratio of linear momenta acquired by above two particles will be:
$\sqrt{2} : 1$
$2\sqrt{2} : 1$
$4\sqrt{2} : 1$
8 : 1
Answer: (b)
Solution
Given $p = \sqrt{2mE} = \sqrt{2mqV}$. The ratio $\frac{p_\alpha}{p_p}$ is given by $$\frac{p_\alpha}{p_p} = \sqrt{\frac{m_\alpha q_\alpha}{m_p q_p}} = \sqrt{\frac{4}{1} \times \frac{2}{1}}$$ This simplifies to $$= \frac{2\sqrt{2}}{1}$$
Question 41
Physics · Atoms · Single correct
Read the following statements: (A) Volume of the nucleus is directly proportional to the mass number. (B) Volume of the nucleus is independent of mass number. (C) Density of the nucleus is directly proportional to the mass number. (D) Density of the nucleus is directly proportional to the cube root of the mass number. (E) Density of the nucleus is independent of the mass number. Choose the correct option from the following options.
and (D) only.
and (E) only.
and (E) only.
and (C) only
Answer: (b)
Solution
Given $R \propto A^{1/3}$. $$V = \frac{4}{3} \pi R^3 \propto A$$ Mass $\propto A$. So density is independent of $A$.
Question 42
Physics · Gravitation · Single correct
An object of mass 1 kg is taken to a height from the surface of earth which is equal to three times the radius of earth. The gain in potential energy of the object will be [If, $g=10 \, \mathrm{m/s^2}$ and radius of earth $= 6400 \, \mathrm{km}$]
48 MJ
24 MJ
36 MJ
12 MJ
Answer: (a)
Solution
The initial potential energy is given by $$U_i = -\frac{GMm}{R}$$ The final potential energy is $$U_f = -\frac{GMm}{4R}$$ The change in potential energy is $$\Delta U = U_f - U_i = \frac{3GMm}{4R}$$ This is equal to $$= \frac{3}{4} mgR$$ Substituting the values, $$= \frac{3}{4} \times 1 \times 10 \times 64 \times 10^5$$ This results in $$= 48 \, MJ$$
Question 43
Physics · Motion in a Straight Line · Single correct
A ball is released from a height $h$. If $t_1$ and $t_2$ be the time required to complete first half and second half of the distance respectively. Then, choose the correct relation between $t_1$ and $t_2$.
$t_1 = (\sqrt{2}) t_2$
$t_1 = (\sqrt{2} - 1) t_2$
$t_2 = (\sqrt{2} + 1) t_1$
$t_2 = (\sqrt{2} - 1) t_1$
Answer: (d)
Solution
For first $\frac{h}{2}$ $$\frac{h}{2} = \frac{1}{2} g t_1^2$$ For total height $h$ $$h = \frac{1}{2} g (t_1 + t_2)^2$$ $$\frac{1}{\sqrt{2}} = \frac{t_1}{t_1 + t_2}$$ $$1 + \frac{t_2}{t_1} = \sqrt{2}$$ $$\frac{t_1}{t_2} = \frac{1}{\sqrt{2} - 1}$$
Question 44
Physics · Laws of Motion · Single correct
Two bodies of masses $m_1 = 5 \, \mathrm{kg}$ and $m_2 = 3 \, \mathrm{kg}$ are connected by a light string going over a smooth light pulley on a smooth inclined plane as shown in the figure. The system is at rest. The force exerted by the inclined plane on the body of mass $m_1$ will be :[Take $g = 10 \, \mathrm{ms^{-2}}$]
30 N
40 N
50 N
60 N
Answer: (b)
Solution
For equilibrium $m_2 g = m_1 g \sin \theta$. $$\sin \theta = \frac{m_2}{m_1} = \frac{3}{5}$$ $$\cos \theta = \frac{4}{5}$$ Normal force on $m_1 = 5g \cos \theta$ $$= 5 \times 10 \times \frac{4}{5} = 40 \, \mathrm{N}$$
Question 45
Physics · Work, Energy and Power · Single correct
If momentum of a body is increased by 20$\%$, then its kinetic energy increases by:
36$\%$
40$\%$
44$\%$
48$\%$
Answer: (c)
Solution
P' = P + $\frac{20}{100}$ P = 1.2 P $\%$ change in KE = $\frac{K' - K}{K}$ $\times$ 100 = $\left$( $\frac{\frac{P'^2}{2m} - \frac{P^2}{2m}}{\frac{P^2}{2m}}$ $\right$) $\times$ 100 = [(1.2)^2 - 1] $\times$ 100 = 44 $\%$
Question 46
Physics · System of Particles and Rotational Motion · Single correct
The torque of a force $5\hat{i} + 3\hat{j} - 7\hat{k}$ about the origin is $\tau$. If the force acts on a particle whose position vector is $2\hat{i} + 2\hat{j} + \hat{k}$, then the value of $\tau$ will be:
A thermodynamic system is taken from an original state D to an intermediate state E by the linear process shown in the figure. Its volume is then reduced to the original volume from E to F by an isobaric process. The total work done by the gas from D to E to F will be
-450 \, $\mathrm{J}$
450 \, $\mathrm{J}$
900 \, $\mathrm{J}$
1350 \, $\mathrm{J}$
Answer: (b)
Solution
Question 48
Physics · Magnetism and Matter · Single correct
The vertical component of the earth's magnetic field is $6 \times 10^{-5} \, \mathrm{T}$ at any place where the angle of dip is $37^\circ$. The earth's resultant magnetic field at that place will be (Given $\tan 37^\circ = \frac{3}{4}$)
$8 \times 10^{-5} \, \mathrm{T}$
$6 \times 10^{-5} \, \mathrm{T}$
$5 \times 10^{-4} \, \mathrm{T}$
$1 \times 10^{-4} \, \mathrm{T}$
Answer: (d)
Solution
Given $\delta = 37^\circ$. The vertical component $B_V = B \sin \delta$. $$6 \times 10^{-5} = B \frac{3}{5}$$ Solving for $B$, we have: $$B = 10 \times 10^{-5} \, \mathrm{T}$$ Thus, $B = 10^{-4} \, \mathrm{T}$.
Question 49
Physics · Kinetic Theory · Single correct
The root mean square speed of smoke particles of mass $5 \times 10^{-17} \, \mathrm{kg}$ in their Brownian motion in air at NTP is approximately. [Given $k = 1.38 \times 10^{-23} \, \mathrm{JK}^{-1}$]
60 mm s$^{-1}$
12 mm s$^{-1}$
15 mm s$^{-1}$
36 mm s$^{-1}$
Answer: (c)
Solution
The root mean square velocity $V_{rms}$ is given by the equation: $$V_{rms} = \sqrt{\frac{3kT}{m}} = \sqrt{\frac{3 \times 1.38 \times 10^{-23} \times 293}{5 \times 10^{-17}}}$$ This is approximately equal to $15 \, mm/s$.
Question 50
Physics · Ray Optics and Optical Instruments · Single correct
Light enters from air into a given medium at an angle of $45^\circ$ with interface of the air-medium surface. After refraction, the light ray is deviated through an angle of $15^\circ$ from its original direction. The refractive index of the medium is :
1.732
1.333
1.414
2.732
Answer: (c)
Solution
Given $i = 45^\circ$. The deviation $D = i - r$. So, $15^\circ = 45 - r \Rightarrow r = 30^\circ$. Using Snell's law, $n_1 \sin i = n_2 \sin r$. Therefore, $1 \cdot \sin 45^\circ = \mu \cdot \sin 30^\circ$. This gives $\frac{1}{\sqrt{2}} = \mu \cdot \frac{1}{2}$. Solving for $\mu$, we get $\mu = \sqrt{2} = 1.414$.
Question 51
Physics · Laws of Motion · Numerical
A tube of length 50 cm is filled completely with an incompressible liquid of mass 250 g and closed at both ends. The tube is then rotated in horizontal plane about one of its ends with a uniform angular velocity $x \sqrt{F}$ rad s$^{-1}$. If $F$ be the force exerted by the liquid at the other end then the value of $x$ will be _____.
Answer: 4
Solution
The force is given by the integral of the differential mass times the square of the angular velocity times the distance. $$F = \int (dm) \omega^2 x$$ Substituting the limits from 0 to $L$, we have: $$= \frac{m}{L} \omega^2 \frac{L^2}{2}$$ Simplifying, $$= \frac{m \omega^2 L}{2}$$ Solving for $\omega$, $$\omega = \sqrt{\frac{2}{mL}} \sqrt{F}$$ Substituting the given values, $$= \sqrt{\frac{2}{0.25 \times 0.5}} \sqrt{F}$$ Simplifying further, $$= \sqrt{16} \sqrt{F}$$ Finally, $$= 4 \sqrt{F}$$
Question 52
Physics · Electromagnetic Waves · Numerical
Nearly 10$\%$ of the power of a 110 \, $\mathrm{W}$ light bulb is converted to visible radiation. The change in average intensities of visible radiation, at a distance of 1 m from the bulb to a distance of 5 m is $a \times 10^{-2} \, \mathrm{W/m^2}$. The value of 'a' will be
Physics · Mechanical Properties of Solids · Numerical
A metal wire of length 0.5 m and cross-sectional area $10^{-4} \, \mathrm{m}^2$ has breaking stress $5 \times 10^8 \, \mathrm{Nm}^{-2}$. A block of 10 kg is attached at one end of the string and is rotating in a horizontal circle. The maximum linear velocity of block will be ____ $\mathrm{ms}^{-1}$.
Physics · Mechanical Properties of Fluids · Numerical
The velocity of a small ball of mass 0.3 g and density 8 g/cc when dropped in a container filled with glycerine becomes constant after some time. If the density of glycerine is 1.3 g/cc, then the value of viscous force acting on the ball will be $x \times 10^{-4} \, \mathrm{N}$, the value of $x$ is ____. [use $g = 10 \, \mathrm{m/s^2}$]
Answer: 25
Solution
Given $F_V + F_B = mg$ (v = constant). $F_V = mg - F_B$ $= \rho_B V g - \rho_L V g$ $= (\rho_B - \rho_L) V g$ $= (8 - 1.3) \times 10^3 \times \frac{0.3 \times 10^{-3}}{8 \times 10^3} \times 10$ $= \frac{6.7 \times 0.3}{8} \times 10^{-2}$ (g = 10) $= \frac{67 \times 3}{8} \times 10^{-4} = 25.125 \times 10^{-4}$ Ans. 25.125
Question 55
Physics · Communication Systems · Numerical
A modulating signal $2\sin(6.28 \times 10^6 t)$ is added to the carrier signal $4\sin (12.56 \times 10^9 t)$ for amplitude modulation. The combined signal is passed through a non-linear square law device. The output is then passed through a band pass filter. The bandwidth of the output signal of band pass filter will be___MHz.
Answer: 2
Solution
Frequencies present in output of square law device $2f_c$, $f_c + f_m$, $f_c$, $f_c - f_m$, $2f_m$, $f_m$. After passing through band bass filter: $f_c + f_m$, $f_c$, $f_c - f_m$. Band width $= 2f_m$ $$= \frac{2\omega_m}{2\pi} = \frac{6.28 \times 10^6}{3.14}$$ $$= 2 \, MHz$$
Question 56
Physics · Mechanical Properties of Solids · Numerical
The speed of a transverse wave passing through a string of length 50 cm and mass 10 g is 60 ms$^{-1}$. The area of cross-section of the wire is 2.0 mm$^2$ and its Young's modulus is $1.2 \times 10^{11}$ Nm$^{-2}$. The extension of the wire over its natural length due to its tension will be $x \times 10^{-5}$ m. The value of $x$ is ______.
The metallic bob of simple pendulum has the relative density 5. The time period of this pendulum is 10 s. If the metallic bob is immersed in water, then the new time period becomes $5\sqrt{x}$ s. The value of $x$ will be _______.
Answer: 5
Solution
The equation for the effective weight is given by: $$mg' = mg - F_B$$ where $F_B$ is the buoyant force. Therefore, the effective acceleration $g'$ is: $$g' = \frac{mg - F_B}{m}$$ Substituting the expression for the buoyant force, we have: $$g' = \frac{\rho_B V g - \rho_w V g}{\rho_B V}$$ Simplifying, we get: $$g' = \left( \frac{\rho_B - \rho_w}{\rho_B} \right) g$$ Substituting the given values: $$g' = \frac{5 - 1}{5} \times g$$ $$g' = \frac{4}{5} g$$ The period $T$ is given by: $$T = 2\pi \sqrt{\frac{\ell}{g}}$$ The new period $T'$ is: $$\frac{T'}{T} = \sqrt{\frac{g}{g'}} = \sqrt{\frac{g}{\frac{4}{5}g}} = \sqrt{\frac{5}{4}}$$ Therefore: $$T' = 5\sqrt{5}$$
A 8 \, $\mathrm{V}$ Zener diode along with a series resistance $R$ is connected across a 20 \, $\mathrm{V}$ supply (as shown in the figure). If the maximum Zener current is 25 \, $\mathrm{mA}$, then the minimum value of $R$ will be _____ \, $\Omega$.
Answer: 480
Solution
Given the equation $\varepsilon - IR - V_z = 0$. Substituting the values, we have: $$20 - IR - 6 = 0$$ Solving for $IR$, we get: $$IR = 12$$ Given $I = 25 \times 10^{-3}$, we substitute to find $R$: $$25 \times 10^{-3} R = 12$$ Solving for $R$, we have: $$R = \frac{12}{25 \times 10^{-3}} = 480 \, \Omega$$
Question 59
Physics · Nuclei · Numerical
Two radioactive materials A and B have decay constants $25\lambda$ and $16\lambda$ respectively. If initially they have the same number of nuclei, then the ratio of the number of nuclei of B to that of A will be "e" after a time $\frac{1}{a\lambda}$. The value of $a$ is________.
A capacitor of capacitance $500 \, \mu \mathrm{F}$ is charged completely using a dc supply of $100 \, \mathrm{V}$. It is now connected to an inductor of inductance $50 \, \mathrm{mH}$ to form an LC circuit. The maximum current in LC circuit will be ______ A.
Answer: 10
Solution
Energy stored in capacitor $$= \frac{1}{2} CV^2 = \frac{1}{2} \times 500 \times 10^{-6} \times 10^4$$ $$= \frac{5}{2} \, \mathrm{J}$$ Current will be maximum when whole energy of capacitor becomes energy of inductor. $$\frac{1}{2} LI^2 = \frac{5}{2}$$ $$I = \sqrt{\frac{5}{L}} = \sqrt{\frac{5}{50 \times 10^{-3}}} = 10 \, \mathrm{A}.$$
Chemistry
Question 61
Chemistry · Some Basic Concepts of Chemistry · Single correct
Consider the reaction $4\mathrm{HNO_3}(l)$+$3\mathrm{KCl}(s)$ $\rightarrow$ $\mathrm{Cl_2}(g)$+$\mathrm{NOCl}(g)$+$2\mathrm{H_2O}(g)$+$3\mathrm{KNO_3}(s)$ The amount of $\mathrm{HNO_3}$ required to produce $110.0\ \mathrm{g}$ of $\mathrm{KNO_3}$ is : (Given : Atomic masses of H, O, N and K are $1,\ 16,\ 14$ and $39$, respectively.)
Given below are the quantum numbers for 4 electrons. A. $n = 3$, $l = 2$, $m_1 = 1$, $m_s = +1/2$ B. $n = 4$, $l = 1$, $m_1 = 0$, $m_s = +1/2$ C. $n = 4$, $l = 2$, $m_1 = -2$, $m_s = -1/2$ D. $n = 3$, $l = 1$, $m_1 = -1$, $m_s = +1/2$ The correct order of increasing energy is :
D < B < A < C
D < A < B < C
B < D < A < C
B < D < C < A
Answer: (b)
Solution
Energy order of subshell decided by $(n+\lambda)$ rule. A $\Rightarrow$ 3d $\Rightarrow n + 1 = 5$ B $\Rightarrow$ 4p $\Rightarrow n + \lambda = 5$ C $\Rightarrow$ 4d $\Rightarrow n + \ell = 6$ D $\Rightarrow$ 3s $\Rightarrow (n+\ell) = 4$ D < A < B < C
Question 63
Chemistry · Some Basic Concepts of Chemistry · Single correct
C(s) + $O_2(g)$ $\rightarrow$ $CO_2(g)$ + 400 $\mathrm{kJ}$ C(s) + $\frac{1}{2}$ $O_2(g)$ $\rightarrow$ CO(g) + 100 $\mathrm{kJ}$ When coal of purity 60$\%$ is allowed to burn in presence of insufficient oxygen, 60$\%$ of carbon is converted into 'CO' and the remaining is converted into '$CO_2$'. The heat generated when 0.6 $\mathrm{kg}$ of coal is burnt is _______.
1600 $\mathrm{kJ}$
3200 $\mathrm{kJ}$
4400 $\mathrm{kJ}$
6600 $\mathrm{kJ}$
Answer: (d)
Solution
Given the reactions: $$\mathrm{C(S) + O_2(g) \rightarrow CO_2(g) + 400 \, kJ}$$ 1 g mole $$\mathrm{C(s) + \frac{1}{2} O_2 (g) \rightarrow CO(g) + 100 \, kJ} (II)$$ Calculating the mass: $$0.6 \times 1000 = 600 \, \mathrm{gm}$$ $$600 \times \frac{60}{100} (Pure Carbon)$$ $$= 360 \, \mathrm{gm} = \frac{360}{12} = 30 \, mole (Pure Carbon)$$ Carbon converted into $\mathrm{CO_2}$: $$= \left( 30 - 30 \times \frac{60}{100} \right)$$ $$= 12 \, mole$$ And carbon converted into $\mathrm{CO}$: $$= 30 \times \frac{60}{100} = 18 \, mole$$ Energy generated during II equation: $$= 18 \times 100$$ $$= 1800 \, \mathrm{kJ}$$ Energy generated during I reaction: $$= 12 \times 400$$ $$= 4800$$ Total: $$= 1800 + 4800 = 6600 \, \mathrm{kJ}$$
Question 64
Chemistry · Equilibrium · Single correct
200 $\mathrm{mL}$ of 0.01 $\mathrm{M}$ HCl is mixed with 400 $\mathrm{mL}$ of 0.01 $\mathrm{M}$ $H_2\mathrm{SO}_4$. The pH of the mixture is .
1.14
1.78
2.34
3.02
Answer: (b)
Solution
For the reaction of HCl and $\mathrm{H_2SO_4}$, the concentration of $[\mathrm{H^+}]$ is calculated as follows: $$[\mathrm{H^+}] = \frac{(0.01 \times 200) + (0.01 \times 2 \times 400)}{600}$$ Simplifying the expression: $$= \frac{2 + 8}{600} = \frac{10}{600} = \frac{1}{60}$$ The pH is given by: $$\mathrm{pH} = -\log \left[ \frac{1}{60} \right]$$ Calculating the pH: $$= 1.78$$
Question 65
Chemistry · Surface Chemistry · Single correct
Given below are the critical temperatures of some of the gases: The gas showing least adsorption on a definite amount of charcoal is:
He
CH_4
CO_2
NH_3
Answer: (a)
Solution
More the critical temp. of gas greater is the ease of liquefaction hence greater is the adsorption.
Question 66
Chemistry · General Principles and Processes of Isolation of Elements · Single correct
Liquation process used for tin (Sn), the metal:
is reacted with acid
is dissolved in water
is brought to molten form which is made to flow on a slope
is fused with NaOH.
Answer: (c)
Solution
Liquation process is used for metal having low melting point such as tin in which they are heated and brought to molten state and made to flow down the slope while impurities with higher melting point left on the top.
Question 67
Chemistry · Hydrogen · Single correct
Given below are two statements. Statement I : Stannane is an example of a molecular hydride. Statement II : Stannane is a planar molecule. In the light of the above statement, choose the most appropriate answer from the options given below :
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.
Statement I is false but Statement II is true.
Answer: (c)
Solution
SnH$_4$ is non planar molecular hydride. Tetrahedral shape, sp$^3$ hybridisation.
Question 68
Chemistry · The s-Block Elements · Single correct
Portland cement contains 'X' to enhance the setting time. What is 'X'?
$CaSO_4 \cdot \frac{1}{2}H_2O$
$\mathrm{CaSO_4 \cdot 2H_2O}$
$\mathrm{CaSO_4}$
$\mathrm{CaCO_3}$
Answer: (b)
Solution
Gypsum ($\mathrm{CaSO_4.2H_2O}$) is used to enhance setting time in portland cement.
Question 69
Chemistry · The p-Block Elements (Group-13 and 14) · Single correct
When borax is heated with CoO on a platinum loop, blue coloured bead formed is largely due to:
B_2O_3
Co(BO_2)_2
CoB_4O_7
Co[B_4O_5(OH)_4]
Answer: (b)
Solution
$Na_2B_4O_7\cdot10H_2O \xrightarrow{\Delta} Na_2B_4O_7+10H_2O$ $Na_2B_4O_7 \xrightarrow{\Delta} 2NaBO_2\ \text{(sodium metaborate)}+B_2O_3$ $B_2O_3+CoO \longrightarrow Co(BO_2)_2\ \text{(cobalt (II) metaborate)}$ Blue Bead
Question 70
Chemistry · The d-and f-Block Elements · Single correct
Which of the following 3d-metal ion will give the lowest enthalpy of hydration ($\Delta_{hyd}H$) when dissolved in water?
$Cr^{2+}$
$Mn^{2+}$
$Fe^{2+}$
$Co^{2+}$
Answer: (b)
Solution
Enthalpy of hydration increases with increase in charge density. $\mathrm{Mn^{+2}}$ has least charge density (as Mn has highest size among the given options) so it will have least enthalpy of hydration.
Question 71
Chemistry · Co-ordination Compounds · Single correct
Octahedral complexes of copper (II) undergo structural distortion (Jahn-Teller). Which one of the given copper (II) complexes will show the maximum structural distortion ? (en=ethylenediamine; $H_2N-CH_2-CH_2-NH_2$)
[$\mathrm{Cu(H_2O)_6}$]$\mathrm{SO_4}$
[$\mathrm{Cu(en)(H_2O)_4}$]$\mathrm{SO_4}$
$\mathrm{cis}$-[$\mathrm{Cu(en)_2Cl_2}$]
$\mathrm{trans}$-[$\mathrm{Cu(en)_2Cl_2}$]
Answer: (a)
Solution
There is unsymmetric filling of $e_g$ subset of $\mathrm{Cu}^{+2}$ ion, while there is symmetrical distribution in $t_{2g}$ set, if the complex has same ligand there will be equal repulsion which leads to symmetrical bond length along $t_{2g}$, but due to uneven filling of electron in $e_g$ subset, either octahedral will be elongated or compressed.
Question 72
Chemistry · The p-Block Elements (Group 15, 16, 17 & 18) · Single correct
Dinitrogen is a robust compound, but reacts at high altitude to form oxides. The oxide of nitrogen that can damage plant leaves and retard photosynthesis is :
$NO$
$\mathrm{NO}_3^-$
$\mathrm{NO}_2$
$\mathrm{NO}_2^-$
Answer: (c)
Solution
The reaction is given by: $$\mathrm{N_2(g) + O_2(g) \rightarrow 2NO(g)}$$ Then: $$\mathrm{2NO(g) + O_2(g) \rightarrow 2NO_2(g)}$$ $\mathrm{NO_2}$ damages plant leaves.
Question 73
Chemistry · Aldehydes, Ketones and Carboxylic Acids · Single correct
Correct structure of $\gamma$-methylcyclohexane carbaldehyde is :
Answer: (a)
Solution
The compound shown is γ-methyl cyclohexane carbaldehyde.
Question 74
Chemistry · Haloalkanes and Haloarenes · Single correct
Compound $\mathrm{A}$ undergoes the following sequence of reactions to give compound $\mathrm{B}$. The correct structure and chirality of compound $\mathrm{B}$ is: [where $\mathrm{Et}$ is $-\mathrm{C_2H_5}$]
Answer: (c)
Solution
Question 75
Chemistry · Organic Chemistry — Some Basic Principles & Techniques · Single correct
Given below are two statements. In the light of the above statement, choose the most appropriate answer from the options given below.
Both Statement I and Statement II are correct
Both Statement I and Statement II are incorrect.
Statement I is correct but Statement II is incorrect.
Statement I is incorrect but Statement II is correct.
Answer: (c)
Solution
Having same configuration.
Question 76
Chemistry · Alcohols, Phenols and Ethers · Single correct
When ethanol is heated with conc. $\mathrm{H_2SO_4}$, a gas is produced. The compound formed, when this gas is treated with cold dilute aqueous solution of Baeyer's reagent, is:
Formaldehyde
Formic acid
Glycol
Ethanoic acid
Answer: (c)
Solution
The reaction starts with $\mathrm{CH_3CH_2OH}$ which is treated with concentrated $\mathrm{H_2SO_4}$ and heat $\Delta$ to form $\mathrm{CH_2=CH_2}$. This is then treated with Bayer's Reagent to form glycol, $\mathrm{CH_2(OH)CH_2(OH)}$.
Question 77
Chemistry · Amines · Single correct
The Hinsberg reagent is :
Answer: (a)
Solution
B.S.C (Benzene sulphonyl chloride) is known as Hinsberg Reagent.
Question 78
Chemistry · Polymers · Single correct
Which of the following is NOT a natural polymer?
Protein
Starch
Rubber
Rayon
Answer: (d)
Solution
Rayon is semisynthetic polymer.
Question 79
Chemistry · Biomolecules · Single correct
Given below are two statements. One is labelled as Assertion A and the other is labelled as Reason R. Assertion A: Amylose is insoluble in water. Reason R: Amylose is a long linear molecule with more than 200 glucose units. In the light of the above statements, choose the correct answer from the options given below.
Both A and R are correct and R is the correct explanation of A.
Both A and R are correct and R is NOT the correct explanation of A.
A is correct but R is not correct.
A is not correct but R is correct.
Answer: (d)
Solution
Amylose is water soluble.
Question 80
Chemistry · Redox Reactions · Single correct
A compound 'X' is a weak acid and it exhibits colour change at pH close to the equivalence point during neutralization of NaOH with CH$_3$COOH. Compound 'X' exists in ionized form in basic medium. The compound 'X' is:
methyl orange
methyl red
phenolphthalein
erichrome Black T
Answer: (c)
Solution
Phenolphthalein is a weak acid and gives color in a basic medium.
Question 81
Chemistry · Solutions · Numerical
$x\ \mathrm{g}$ of molecular oxygen $(\mathrm{O_2})$ is mixed with $200\,\mathrm{g}$ of neon $(\mathrm{Ne})$. The total pressure of the non-reactive mixture of $\mathrm{O_2}$ and $\mathrm{Ne}$ in the cylinder is $25\,\mathrm{bar}$. The partial pressure of $\mathrm{Ne}$ is $20\,\mathrm{bar}$ at the same temperature and volume. The value of $x$ is \_\_\_\_. [Given: Molar mass of $\mathrm{O_2} = 32\,\mathrm{g\,mol^{-1}}$. Molar mass of $\mathrm{Ne} = 20\,\mathrm{g\,mol^{-1}}$]
Answer: 80
Solution
Given $\mathrm{O_2 + Ne}$ with $x \, \mathrm{gm}$ and $200 \, \mathrm{gm}$. The total pressure $P_{total} = 25 \, \mathrm{bar}$ and $P_{\mathrm{Ne}} = 20 \, \mathrm{bar}$. The pressure of $\mathrm{O_2}$ is given by: $$P_{\mathrm{O_2}} + P_{\mathrm{Ne}} = 25$$ $$P_{\mathrm{O_2}} = 25 - 20 = 5 \, \mathrm{bar}$$ Using the equation: $$\frac{x}{32} + \frac{200}{20}$$ We have: $$\frac{1}{5} = \frac{\frac{x}{32}}{\frac{x}{32} + 10}$$ Simplifying: $$1 = \frac{x \times 32}{32(x + 320)}$$ Solving for $x$: $$5x = x + 320$$ $$4x = 320$$ $$x = \frac{320}{4} = 80 \, \mathrm{gm}$$
Question 82
Chemistry · Chemical Bonding and Molecular Structure · Numerical
Consider, $PF_5, BrF_5, PCl_3, SF_6, [ICl_4]^-, ClF_3$ and $IF_5$. Amongst the above molecule(s)/ion(s), the number of molecule(s)/ion(s) having $sp^3d^2$ hybridisation is ____.
Answer: 4
Solution
Question 83
Chemistry · Solutions · Numerical
$1.80\,\mathrm{g}$ of solute A was dissolved in $62.5\,\mathrm{cm^3}$ of ethanol and freezing point of the solution was found to be $155.1\,\mathrm{K}$. The molar mass of solute A is \_\_\_\_ $\mathrm{g\,mol^{-1}}$. [Given: Freezing point of ethanol is $156.0\,\mathrm{K}$. Density of ethanol is $0.80\,\mathrm{g\,cm^{-3}}$. Freezing point depression constant of ethanol is $2.00\,\mathrm{K\,kg\,mol^{-1}}$]
For a cell, $\mathrm{Cu(s) | Cu^{2+}(0.001 \, M) | Ag^{+}(0.01 \, M) | Ag(s)}$ the cell potential is found to be $0.43 \, \mathrm{V}$ at $298 \, \mathrm{K}$. The magnitude of standard electrode potential for $\mathrm{Cu^{2+}/Cu}$ is _______ $\times 10^{-2} \, \mathrm{V}$. $\left[ \text{Given: } E^{\Theta}_{\mathrm{Ag^{+}/Ag}} = 0.80 \, \mathrm{V} \text{ and } \frac{2.303RT}{F} = 0.06 \, \mathrm{V} \right]$
Chemistry · Chemical Kinetics and Nuclear Chemistry · Numerical
Assuming 1 $\mu$ g of trace radioactive element X with a half life of 30 years is absorbed by a growing tree. The amount of X remaining in the tree after 100 years is ___ $\times$ 10^{-1} $\mu$ g. [Given : $\ln$ 10 = 2.303; $\log$ 2 = 0.30]
Answer: 1
Solution
Given the equation $$t = \frac{1}{\lambda} \ln \left( \frac{a}{a-x} \right)$$. We have $$100 = \frac{30}{\ln 2} \ln \left( \frac{1}{w} \right)$$. Solving for $$w$$, we get $$\frac{1}{w} = 10$$. Therefore, $$W = 0.1 \times \mu g$$. The answer is $$1 \times 10^{-1} \mu g$$.
Question 86
Chemistry · Co-ordination Compounds · Numerical
Sum of oxidation state (magnitude) and coordination number of cobalt in $Na[Co(bpy)Cl_4]$ is __. (Given bpy = )
Chemistry · The p-Block Elements (Group 15, 16, 17 & 18) · Numerical
Consider the following sulphure based oxoacids. $\mathrm{H_2SO_3}$, $\mathrm{H_2SO_4}$, $\mathrm{H_2S_2O_8}$ and $\mathrm{H_2S_2O_7}$. Amongst these oxoacids, the number of those with peroxo(O-O) bond is
Answer: 1
Solution
Question 88
Chemistry · Some Basic Concepts of Chemistry · Numerical
A 1.84 $\mathrm{mg}$ sample of polyhydric alcoholic compound 'X' of molar mass 92.0 $\mathrm{g/mol}$ gave 1.344 $\mathrm{mL}$ of $\mathrm{H}_2$ gas at STP. The number of alcoholic hydrogens present in compound 'X' is ____.
Chemistry · Aldehydes, Ketones and Carboxylic Acids · Numerical
The number of stereoisomers formed in a reaction of ($\pm$) Ph(C=O) C(OH)(CN)Ph with HCN is .
Answer: 4
Solution
The reaction of the given compound with HCN results in the formation of a compound with 3 stereoisomers.
Question 90
Chemistry · Chemistry in Everyday Life · Numerical
The number of chlorine atoms in bithionol is ___ .
Answer: 4
Solution
Bithinol contains two benzene rings connected by a sulfur atom. Each benzene ring has two chlorine atoms attached. Therefore, the total number of chlorine atoms is 4.