JEE Main 22 January 2025 Shift 2 question paper with solutions

JEE Main 22 January 2025 Shift 2: 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 · Binomial Theorem · Single correct

Let $\alpha$, $\beta$, $\gamma$ and $\delta$ be the coefficients of $x^7$, $x^5$, $x^3$ and $x$ respectively in the expansion of $$\left( x + \sqrt{x^3 - 1} \right)^5 + \left( x - \sqrt{x^3 - 1} \right)^5, \ x > 1.$$ If $u$ and $v$ satisfy the equations $$\alpha u + \beta v = 18$$ $$\gamma u + \delta v = 20$$ then $u + v$ equals :

  1. 5
  2. 3
  3. 4
  4. 8

Answer: (a)

Solution

Given $$\left( x + \sqrt{x^3 - 1} \right)^5 + \left( x - \sqrt{x^3 - 1} \right)^5$$ Subtract $$\left[ 5C_0 x^5 + 5C_1 x^4 \left( \sqrt{x^3 - 1} \right) + \ldots + 5C_5 \left( \sqrt{x^3 - 1} \right)^5 \right]$$ Add $$\left[ 5C_0 x^5 - 5C_1 x^4 \left( \sqrt{x^3 - 1} \right) + \ldots - 5C_5 \left( \sqrt{x^3 - 1} \right)^5 \right]$$ This simplifies to $$= 2 \left[ x^5 + 5C_2 x^3 \left( x^3 - 1 \right) + 5C_4 \left( x^3 - 1 \right)^2 \right]$$ $$= 10x^7 + 20x^6 + 2x^5 - 20x^4 + 10x$$ Now $$\alpha = 10, \beta = 2, \gamma = -20, \delta = 10$$ Also, $$\begin{align*} 10u + 2v &= 18 \\ -20u + 10v &= 20 \end{align*}$$ Solving gives $$u = 1, v = 4$$ Thus, $$u + v = 5$$

Question 2

Maths · Permutations and Combinations · Single correct

In a group of 3 girls and 4 boys, there are two boys $B_1$ and $B_2$. The number of ways, in which these girls and boys can stand in a queue such that all the girls stand together, all the boys stand together, but $B_1$ and $B_2$ are not adjacent to each other, is:

  1. 96
  2. 144
  3. 120
  4. 72

Answer: (b)

Solution

Total - when $B_1$ and $B_2$ are together $$= 2!(3!4!) - 2!(3!(3!2!)) = 144$$

Question 3

Maths · Conic Sections · Single correct

Let P(4, 4$\sqrt{3}$) be a point on the parabola $y^2 = 4ax$ and PQ be a focal chord of the parabola. If M and N are the foot of perpendiculars drawn from P and Q respectively on the directrix of the parabola, then the area of the quadrilateral PQMN is equal to:

  1. 17$\sqrt{3}$
  2. $\frac{263\sqrt{3}}{8}$
  3. $\frac{34\sqrt{3}}{3}$
  4. $\frac{343\sqrt{3}}{8}$

Answer: (d)

Solution

$(4,4\sqrt3)$ lies on $y^2=4ax$ $\Rightarrow\ 48=4a\cdot4$ $\Rightarrow\ 4a=12$ $\Rightarrow\ y^2=12x$ is equation of parabola Now, parameter of $P$ is $t_1=\dfrac{2}{\sqrt3}$ $\Rightarrow$ Parameter of $Q$ is $t_2=-\dfrac{\sqrt3}{2}$ $\Rightarrow\ Q\left(\dfrac94,-3\sqrt3\right)$ Area of trapezium $PQNM$ $=\dfrac12\,MN\cdot(PM+QN)$ $=\dfrac12\,MN\cdot(PS+QS)$ $=\dfrac12\,MN\cdot PQ$ $=\dfrac12\cdot7\sqrt3\cdot\dfrac{49}{4}$ $=(343)\dfrac{\sqrt3}{8}=3$

Question 4

Maths · Matrices · Single correct

For a $3 \times 3$ matrix $M$, let trace $(M)$ denote the sum of all the diagonal elements of $M$. Let $A$ be a $3 \times 3$ matrix such that $|A| = \frac{1}{2}$ and trace $(A) = 3$. If $B = adj(adj(2A))$, then the value of $|B| + trace (B)$ equals:

  1. 56
  2. 132
  3. 174
  4. 280

Answer: (d)

Solution

Given $\mathrm{tr}(A) = 3$ and $|A| = \frac{1}{2}$. Now, $B = \mathrm{adj}(\mathrm{adj}(2A)) = |2A|^{3-2} \cdot (2A)$. $$= 2^3 |A| \cdot 2A = 8A$$ Therefore, $\mathrm{tr}(B) = 8 \, \mathrm{tr}(A) = 24$ and $|B| = |8A| = 8^3 \cdot \frac{1}{2} = 256$. Thus, $\mathrm{trace}(B) + |B| = 24 + 256 = 280$.

Question 5

Maths · Sequences and Series · Single correct

Suppose that the number of terms in an A.P. is $2k, k \in \mathbb{N}$. If the sum of all odd terms of the A.P. is 40, the sum of all even terms is 55 and the last term of the A.P. exceeds the first term by 27, then $k$ is equal to:

  1. 6
  2. 5
  3. 8
  4. 4

Answer: (b)

Solution

Let the A.P. be $a, a + 2, a + 2d, \ldots, a + (2k - 1)d$ Now, $a + a + 2d + a + 4d + \ldots + a + (2k - 2)d = 40$ $$ka + 2d + 4d + \ldots + (2k - 2)d = 40$$ $$\Rightarrow ka + \frac{k - 1}{2} [2d + 2kd - 2d] = 40$$ $$\Rightarrow ka + k(k - 1)d = 40 \ldots (1)$$ And $a + d + a + 3d + \ldots + a + (2k - 1)d = 55$ $$\Rightarrow ka + \frac{k}{2} (d + 2kd - d) = 55$$ $$\Rightarrow ka + k^2 d = 55 \ldots (2)$$ Also, $a + (2k - 1)d - a = 27$ $$\Rightarrow (2k - 1)d = 27 \Rightarrow d = \frac{27}{2k - 1} \ldots (3)$$ From equation (1) and (2) $$k^2 d - kd - k^2 d = -15$$ $$\Rightarrow d = \frac{15}{k}$$ From equation (3) and (4) $$\frac{27}{2k - 1} = \frac{15}{k}$$ $$27k = 30k - 15$$ $$\Rightarrow 3k = 15$$ $$\Rightarrow k = 5$$

Question 6

Maths · Three Dimensional Geometry · Single correct

Let a line pass through two distinct points $P(-2, -1, 3)$ and $Q$, and be parallel to the vector $3\hat{i} + 2\hat{j} + 2\hat{k}$. If the distance of the point $Q$ from the point $R(1, 3, 3)$ is $5$, then the square of the area of $\triangle PQR$ is equal to:

  1. 148
  2. 136
  3. 144
  4. 140

Answer: (b)

Solution

Equation of line $PQ$ is: $$\frac{x+2}{3} = \frac{y+1}{2} = \frac{z-3}{2} = r\ (\text{say})$$ Let coordinate of $Q = (3r-2,\ 2r-1,\ 2r+3)$. Since $PR = 5$, then $$(3r-2-1)^2 + (2r-1-3)^2 + (2r+3-3)^2 = 25$$ Therefore, $r = 0$ or $2$. Thus, coordinate of $Q = (4, 3, 7)$. Therefore, square of area of $\triangle PQR = \left|\dfrac{1}{2}\overrightarrow{PQ} \times \overrightarrow{PR}\right|^2$ $$= \left|\frac{1}{2}\left(6\hat{i} + 4\hat{j} + 4\hat{k}\right) \times \left(3\hat{i} + 4\hat{j}\right)\right|^2$$ $$= \left|-8\hat{i} + 6\hat{j} + 6\hat{k}\right|^2 = 136$$

Question 7

Maths · Limits and Derivatives · Single correct

If $\lim_{x \to \infty} \left( \left( \frac{e}{1-e} \right) \left( \frac{1}{e} - \frac{x}{1+x} \right) \right)^x = \alpha$, then the value of $\frac{\log_e \alpha}{1+\log_e \alpha}$ equals:

  1. $e^{-1}$
  2. $e^2$
  3. $e^{-2}$
  4. $e$

Answer: (d)

Solution

Given $\($ $\alpha$ = $\lim$_{x $\to$ $\infty$} $\left$( $\left$( $\frac{e}{1-e}$ $\right$) $\left$( $\frac{1}{e}$ - $\frac{x}{1+x}$ $\right$) $\right$)^x $\)$ ($\($1^$\infty$$\)$ form). Therefore, $\($ $\alpha$ = e^L $\)$. Where $\($ L = $\lim$_{x $\to$ $\infty$} x $\left$( $\left$( $\frac{e}{1-e}$ $\right$) $\left$( $\frac{1}{e}$ - $\frac{x}{1+x}$ $\right$) - 1 $\right$) $\)$. $\($ $\Rightarrow$ L = $\lim$_{x $\to$ $\infty$} $\left$( $\frac{e}{1-e}$ $\right$) x $\left$( $\frac{1}{e}$ - $\frac{x}{1+x}$ - $\left$( $\frac{1-e}{e}$ $\right$) $\right$) $\)$. $\($ $\Rightarrow$ L = $\frac{e}{1-e}$ $\lim$_{x $\to$ $\infty$} x $\left$( $\frac{1-x}{x(1+x)}$ $\right$) $\)$. $\($ $\Rightarrow$ L = $\frac{e}{1-e}$ $\lim$_{x $\to$ $\infty$} $\frac{x}{x+1}$ $\)$. $\($ $\Rightarrow$ L = $\frac{e}{1-e}$ $\cdot$ 1 $\)$. $\($ $\Rightarrow$ L = $\frac{1-e}{e}$ $\)$. Therefore, $\($ $\alpha$ = e^{$\frac{1-e}{e}$} $\Rightarrow$ $\log$ $\alpha$ = $\frac{e}{1-e}$ $\)$. Therefore, the required value $\($ = $\frac{e}{1-e}$ $\)$ $\($ = e $\)$.

Question 8

Maths · Integrals · Single correct

Let $f(x) = \int_{0}^{x^2} \frac{t^2 - 8t + 15}{e^t} \, dt, \ x \in \mathbb{R}$. Then the numbers of local maximum and local minimum points of $f$, respectively, are:

  1. 2 and 3
  2. 2 and 2
  3. 3 and 2
  4. 1 and 3

Answer: (a)

Solution

Given $$f(x) = \int_0^{x^2} t^2 - 8t + 15 \, dt, x \in \mathbb{R}$$ $$f'(x) = x^4 - 8x^2 + 15$$ $$e^{x^2} (2x) = 0$$ $$\Rightarrow 2 \times (x^2 - 5)(x^2 - 3) = 0$$ $$\Rightarrow e^{x^2}$$ $$\Rightarrow x(x + \sqrt{5})(x - \sqrt{5})(x + \sqrt{3})(x - \sqrt{3}) = 0$$ By using wavy curve method Number of local maximum = 2 Number of local minimum = 3

Question 9

Maths · Three Dimensional Geometry · Single correct

The perpendicular distance, of the line $\frac{x-1}{2} = \frac{y+2}{-1} = \frac{z+3}{2}$ from the point $P(2, -10, 1)$, is :

  1. 6
  2. 5$\sqrt{2}$
  3. 4$\sqrt{3}$
  4. 3$\sqrt{5}$

Answer: (d)

Solution

Given the point $P(2, -10, 1)$ and the direction vector $\mathbf{n} = 2\hat{i} - \hat{j} + 2\hat{k}$, we find the coordinates of point $A$ on the line. The parametric equations are given by: $$\frac{x - 1}{2} = \frac{y + 2}{-1} = \frac{z + 3}{2} = \lambda (let)$$ This gives the point $A$ as $(2\lambda + 1, -\lambda - 2, 2\lambda - 3)$. The condition for $\overrightarrow{PA} \cdot \overrightarrow{n} = 0$ is: $$\Rightarrow (2\lambda - 1)2 + (-\lambda + 8)(-1) + (2\lambda - 4)2 = 0$$ $$\Rightarrow 4\lambda - 2 + \lambda - 8 + 4\lambda - 8 = 0$$ $$\Rightarrow 9\lambda - 18 = 0 \Rightarrow \lambda = 2$$ Therefore, $A(5, -4, 1)$. The distance $AP$ is: $$AP = \sqrt{3^2 + 6^2 + 0^2} = \sqrt{45} = 3\sqrt{5}$$

Question 10

Maths · Differential Equations · Single correct

If $x = f(y)$ is the solution of the differential equation $$ (1 + y^2) + \left( x - 2e^{\tan^{-1} y} \right) \frac{dy}{dx} = 0, y \in \left( -\frac{\pi}{2}, \frac{\pi}{2} \right) $$ with $f(0) = 1$, then $f\left( \frac{1}{\sqrt{3}} \right)$ is equal to:

  1. $e^{\pi/12}$
  2. $e^{\pi/4}$
  3. $e^{\pi/3}$
  4. $e^{\pi/6}$

Answer: (d)

Solution

$\dfrac{dx}{dy}+\dfrac{x}{1+y^2}=\dfrac{2e^{\tan^{-1}y}}{1+y^2}$ I.F. $=e^{\tan^{-1}y}$ $\therefore\ xe^{\tan^{-1}y} =\int\dfrac{2\left(e^{\tan^{-1}y}\right)^2}{1+y^2}\,dy$ Put $\tan^{-1}y=t,\qquad \dfrac{dy}{1+y^2}=dt$ $\therefore\ xe^{\tan^{-1}y} =\int2e^{2t}\,dt$ $xe^{\tan^{-1}y}=e^{2\tan^{-1}y}+c$ $\therefore\ x=e^{\tan^{-1}y}+ce^{-\tan^{-1}y}$ $\because\ y=0,\;x=1$ $\therefore\ 1=1+c \;\Rightarrow\; c=0$ $\therefore\ x=e^{\tan^{-1}y}$ $\therefore\ y=\dfrac{1}{\sqrt3},\quad x=e^{\pi/6}$

Question 11

Maths · Integrals · Single correct

If $\int e^x\left(\dfrac{x\sin^{-1}x}{\sqrt{1-x^2}} + \dfrac{\sin^{-1}x}{(1-x^2)^{3/2}} + \dfrac{x}{1-x^2}\right)dx = g(x) + C$, where $C$ is the constant of integration, then $g\left(\dfrac{1}{2}\right)$ equals :

  1. $\dfrac{\pi}{4}\sqrt{\dfrac{e}{3}}$
  2. $\dfrac{\pi}{6}\sqrt{\dfrac{e}{3}}$
  3. $\dfrac{\pi}{4}\sqrt{\dfrac{e}{2}}$
  4. $\dfrac{\pi}{6}\sqrt{\dfrac{e}{2}}$

Answer: (b)

Solution

Given $$\frac{d}{dx} \left( \frac{x \cdot \sin^{-1} x}{\sqrt{1-x^2}} \right) - \sin^{-1} x \cdot \left( \frac{1 \cdot \sqrt{1-x^2} + \frac{x \cdot 2x}{2\sqrt{1-x^2}}}{1-x^2} \right)$$ This simplifies to $$= \frac{x}{\sqrt{1-x^2}} \cdot \frac{1}{\sqrt{1-x^2}}$$ $$= \frac{\sin^{-1} x}{(1-x^2)^{3/2}} + \frac{x}{1-x^2}$$ Hence, $$I = \int e^x \left( f(x) + f'(x) \right) \, dx$$ $$= e^x \cdot f(x) + C$$ $$I = e^x \cdot \frac{x \cdot \sin^{-1} x}{\sqrt{1-x^2}} + C = g(x) + C$$ Thus, $$g(x) = \frac{x e^x \sin^{-1} x}{\sqrt{1-x^2}}$$ and $$g(1/2) = \frac{\pi}{6} \frac{1}{e} \sqrt{3}$$

Question 12

Maths · Complex Numbers and Quadratic Equations · Single correct

Let $\alpha_\theta$ and $\beta_\theta$ be the distinct roots of $2x^2 + (\cos \theta)x - 1 = 0, \theta \in (0, 2\pi)$. If $m$ and $M$ are the minimum and the maximum values of $\alpha_\theta^4 + \beta_\theta^4$, then $16(M + m)$ equals:

  1. 24
  2. 25
  3. 17
  4. 27

Answer: (b)

Solution

To solve the problem, we start by using the properties of the roots of the quadratic equation. The quadratic equation given is $2x^2 + (\cos \theta)x - 1 = 0$. Let $\alpha_\theta$and$\beta_\theta$ be the roots. By Vieta's formulas, we know: $$ \alpha_\theta + \beta_\theta = -\frac{\cos \theta}{2} $$ $$ \alpha_\theta \beta_\theta = -\frac{1}{2} $$ We need to find the minimum and maximum values of $\alpha_\theta^4 + \beta_\theta^4$. We can express $\alpha_\theta^4 + \beta_\theta^4$in terms of$\alpha_\theta + \beta_\theta$and$\alpha_\theta \beta_\theta$. Using the identity for the sum of fourth powers, we have: $$ \alpha_\theta^4 + \beta_\theta^4 = (\alpha_\theta^2 + \beta_\theta^2)^2 - 2(\alpha_\theta \beta_\theta)^2 $$ First, we need to find $\alpha_\theta^2 + \beta_\theta^2$. We can use the identity: $$ \alpha_\theta^2 + \beta_\theta^2 = (\alpha_\theta + \beta_\theta)^2 - 2\alpha_\theta \beta_\theta $$ Substituting the values from Vieta's formulas: $$ \alpha_\theta^2 + \beta_\theta^2 = \left(-\frac{\cos \theta}{2}\right)^2 - 2\left(-\frac{1}{2}\right) = \frac{\cos^2 \theta}{4} + 1 $$ Now, we substitute this back into the expression for $\alpha_\theta^4 + \beta_\theta^4$: $$ \alpha_\theta^4 + \beta_\theta^4 = \left(\frac{\cos^2 \theta}{4} + 1\right)^2 - 2\left(-\frac{1}{2}\right)^2 = \left(\frac{\cos^2 \theta}{4} + 1\right)^2 - 2 \cdot \frac{1}{4} = \left(\frac{\cos^2 \theta}{4} + 1\right)^2 - \frac{1}{2} $$ Next, we expand $\left(\frac{\cos^2 \theta}{4} + 1\right)^2$: $$ \left(\frac{\cos^2 \theta}{4} + 1\right)^2 = \left(\frac{\cos^2 \theta}{4}\right)^2 + 2 \cdot \frac{\cos^2 \theta}{4} \cdot 1 + 1^2 = \frac{\cos^4 \theta}{16} + \frac{\cos^2 \theta}{2} + 1 $$ So, we have: $$ \alpha_\theta^4 + \beta_\theta^4 = \frac{\cos^4 \theta}{16} + \frac{\cos^2 \theta}{2} + 1 - \frac{1}{2} = \frac{\cos^4 \theta}{16} + \frac{\cos^2 \theta}{2} + \frac{1}{2} $$ To find the minimum and maximum values of this expression, we let $u = \cos^2 \theta$. Since $\cos^2 \theta$ranges from 0 to 1,$u$ also ranges from 0 to 1. The expression becomes: $$ f(u) = \frac{u^2}{16} + \frac{u}{2} + \frac{1}{2} $$ We need to find the minimum and maximum values of $f(u)$for$u \in [0, 1]$. First, we find the critical points by taking the derivative of $f(u)$ and setting it to zero: $$ f'(u) = \frac{2u}{16} + \frac{1}{2} = \frac{u}{8} + \frac{1}{2} $$ Setting $f'(u) = 0$: $$ \frac{u}{8} + \frac{1}{2} = 0 \implies \frac{u}{8} = -\frac{1}{2} \implies u = -4 $$ Since $u = -4$is not in the interval$[0, 1]$, we only need to evaluate $f(u)$at the endpoints$u = 0$and$u = 1$: $$ f(0) = \frac{0^2}{16} + \frac{0}{2} + \frac{1}{2} = \frac{1}{2} $$ $$ f(1) = \frac{1^2}{16} + \frac{1}{2} + \frac{1}{2} = \frac{1}{16} + 1 = \frac{17}{16} $$ Thus, the minimum value $m$of$\alpha_\theta^4 + \beta_\theta^4$is$\frac{1}{2}$and the maximum value$M$is$\frac{17}{16}$. We need to find $16(M + m)$: $$ 16\left(\frac{17}{16} + \frac{1}{2}\right) = 16\left(\frac{17}{16} + \frac{8}{16}\right) = 16 \cdot \frac{25}{16} = 25 $$ Therefore, the correct option is $\boxed{b}$.

Question 13

Maths · Relations and Functions · Single correct

Let $A = \{1, 2, 3, 4\}$ and $B = \{1, 4, 9, 16\}$. Then the number of many-one functions $f : A \to B$ such that $1 \in f(A)$ is equal to :

  1. 151
  2. 139
  3. 163
  4. 127

Answer: (a)

Solution

Given sets $A = \{1, 2, 3, 4\}$ and $B = \{1, 4, 9, 16\}$. Total number of functions is $4^4$. Total number of one-one functions is $4!$. Total number of many-one functions is $4^4 - 4! = 232$. Total number of many-one functions in which $1 \notin f(A)$ is $3 \times 3 \times 3 \times 3 = 81$. Therefore, total number of many-one functions $1 \notin f(A)$ is $$= 232 - 81$$ $$= 151$$

Question 14

Maths · Determinants · Single correct

If the system of linear equations : $$x + y + 2z = 6$$ $$2x + 3y + az = a + 1$$ $$-x - 3y + bz = 2b$$ where $a, b \in \mathbb{R}$, has infinitely many solutions, then $7a + 3b$ is equal to :

  1. 16
  2. 12
  3. 22
  4. 9

Answer: (a)

Solution

The given equations are $$x + y + 2z = 6$$ $$2x + 3y + az = a + 1$$ $$-x - 3y + bz = 2b,$$ where $a, b, z \in \mathbb{R}$. For infinite many solutions: $$D = D_1 = D_2 = D_3 = 0$$ Therefore, $$D = \begin{vmatrix} 1 & 1 & 2 \\ 2 & 3 & a \\ -1 & -3 & b \end{vmatrix} = 2a + b - 6$$ $$D_1 = \begin{vmatrix} 6 & 1 & 2 \\ a + 1 & 3 & a \\ 2b & -3 & b \end{vmatrix} = 12a + 5b + ab - 6$$ $$D_2 = \begin{vmatrix} 1 & 6 & 2 \\ 2 & a + 1 & a \\ -1 & 2b & b \end{vmatrix} = -4a - 3b - ab + 2$$ and $$D_3 = \begin{vmatrix} 1 & 1 & 6 \\ 2 & 3 & a + 1 \\ -1 & -3 & 2b \end{vmatrix} = 2a + 2b - 16$$ From above relations $$a = -2, b = 10$$ Therefore, $7a + 3b = 16$

Question 15

Maths · Vector Algebra · Single correct

Let $\vec{a}$ and $\vec{b}$ be two unit vectors such that the angle between them is $\frac{\pi}{3}$. If $\lambda \vec{a} + 2 \vec{b}$ and $3 \vec{a} - \lambda \vec{b}$ are perpendicular to each other, then the number of values of $\lambda$ in $[-1, 3]$ is:

  1. 2
  2. 1
  3. 0
  4. 3

Answer: (c)

Solution

Given $\hat{a} \cdot \hat{b} = \frac{1}{2}$. Now $(\lambda \hat{a} + 2 \hat{b}) \cdot (3 \hat{a} - \lambda \hat{b}) = 0$. $$3 \lambda \hat{a} \cdot \hat{a} - \lambda^2 \hat{a} \cdot \hat{b} + 6 \hat{a} \cdot \hat{b} - 2 \lambda \hat{b} \cdot \hat{b} = 0$$ $$3 \lambda - \frac{\lambda^2}{2} + 3 - 2 \lambda = 0$$ $$\lambda^2 - 2 \lambda - 6 = 0$$ $$\lambda = 1 \pm \sqrt{7}$$ Therefore, number of values $= 0$.

Question 16

Maths · Conic Sections · Single correct

Let $E : \frac{x^2}{a^2} + \frac{y^2}{b^2} = 1$, $a > b$ and $H : \frac{x^2}{A^2} - \frac{y^2}{B^2} = 1$. Let the distance between the foci of $E$ and the foci of $H$ be $2\sqrt{3}$. If $a - A = 2$, and the ratio of the eccentricities of $E$ and $H$ is $\frac{1}{3}$, then the sum of the lengths of their latus rectums is equal to:

  1. 10
  2. 9
  3. 8
  4. 7

Answer: (c)

Solution

Given $\frac{x^2}{a^2} + \frac{y^2}{b^2} = 1$ foci are $(ae, 0)$ and $(-ae, 0)$. $\frac{x^2}{A^2} + \frac{y^2}{B^2} = 1$ foci are $(Ae', 0)$ and $(-Ae', 0)$. Therefore, $2ae = 2\sqrt{3} \Rightarrow ae = \sqrt{3}$ and $2Ae' = 2\sqrt{3} \Rightarrow Ae' = \sqrt{3}$. Thus, $ae = Ae' \Rightarrow \frac{e}{e'} = \frac{A}{a}$. This implies $\frac{1}{3} = \frac{A}{a} \Rightarrow a = 3A$. Now $a - A = 2 \Rightarrow a - \frac{a}{3} = 2 \Rightarrow a = 3$ and $A = 1$. $Ae = \sqrt{3} \Rightarrow e = \frac{1}{\sqrt{3}}$ and $e' = \sqrt{3}$. $b^2 = a^2 (1 - e^2)$ $b^2 = 6$ and $B^2 = A^2 ((e')^2 - 1) = (2) \Rightarrow B^2 = 2$. Sum of LR = $\frac{2b^2}{a} + \frac{2B^2}{A} = 8$.

Question 17

Maths · Probability (Advanced) · Single correct

If $A$ and $B$ are two events such that $P(A \cap B) = 0.1$, and $P(A \mid B)$ and $P(B \mid A)$ are the roots of the equation $$12x^2 - 7x + 1 = 0,$$ then the value of $$\frac{P(\overline{A} \cup \overline{B})}{P(\overline{A} \cap \overline{B})}$$ is :

  1. $\frac{4}{3}$
  2. $\frac{7}{4}$
  3. $\frac{5}{3}$
  4. $\frac{9}{4}$

Answer: (d)

Solution

Given $P(A \cap B) = 0.1$, $P(A \mid B)$ and $P(B \mid A)$ are the roots of the equation $12x^2 - 7x + 1 = 0$. $$P(A \mid B)P(B \mid A) = \frac{1}{12}$$ Therefore, $$\frac{P(A \cap B)}{P(B)} \times \frac{P(A \cap B)}{P(A)} = \frac{1}{12}$$ This implies $$P(A)P(B) = 12(0.1)^2 = 0.12$$ Also, $$P(A \mid B) + P(B \mid A) = \frac{7}{12}$$ Thus, $$P(A \cap B) \left( \frac{1}{P(B)} + \frac{1}{P(A)} \right) = \frac{7}{12}$$ Therefore, $$P(A) + P(B) = \frac{7}{12} \times \frac{0.12}{0.1}$$ This gives $$P(A) + P(B) = 0.7$$ Now, $$\frac{P(\bar{A} \cup \bar{B})}{P(\bar{A} \cap \bar{B})} = \frac{P(A \cap B)}{P(A \cup B)}$$ This simplifies to $$= \frac{1 - P(A \cap B)}{1 - P(A \cup B)}$$ Which is $$= \frac{1 - 0.1}{1 - (0.7 - 0.1)} = \frac{0.9}{0.4} = \frac{9}{4}$$

Question 18

Maths · Trigonometric Functions · Single correct

The sum of all values of $\theta \in [0, 2\pi]$ satisfying $2 \sin^2 \theta = \cos 2\theta$ and $2 \cos^2 \theta = 3 \sin \theta$ is

  1. $4\pi$
  2. $\frac{5\pi}{6}$
  3. $\pi$
  4. $\frac{\pi}{2}$

Answer: (c)

Solution

Given $2 \sin^2 \theta = \cos 2\theta$. $2 \sin^2 \theta = 1 - 2 \sin^2 \theta$ $$4 \sin^2 \theta = 1$$ $$\sin^2 \theta = \frac{1}{4}$$ $$\sin \theta = \pm \frac{1}{2}$$ $2 \cos^2 \theta = 3 \sin \theta$ $$2 - 2 \sin^2 \theta + 3 \sin \theta - 2 = 0$$ $$(2 \sin \theta - 1)(2 \sin \theta - 2) = 0$$ $$\sin \theta = \frac{1}{2}$$ So common equation which satisfy both equations is $\sin \theta = \frac{1}{2}$. $$\theta = \frac{\pi}{6}, \frac{5\pi}{6} (\theta \in [0, 2\pi])$$ Sum = $\pi$

Question 19

Maths · Complex Numbers and Quadratic Equations · Single correct

Let the curve $z(1+i) + \bar{z}(1-i) = 4, z \in \mathbb{C}$, divide the region $|z-3| \leq 1$ into two parts of areas $\alpha$ and $\beta$. Then $|\alpha - \beta|$ equals:

  1. $1 + \frac{\pi}{2}$
  2. $1 + \frac{\pi}{3}$
  3. $1 + \frac{\pi}{6}$
  4. $1 + \frac{\pi}{4}$

Answer: (a)

Solution

Let $z = x + iy$. $$(x + iy)(1 + i) + (x - iy)(1 - i) = 4$$ $$x + ix + iy - y + x - ix - iy - y = 4$$ $$2x - 2y = 4$$ $$x - y = 2$$ $$|z - 3| \leq 1$$ $$(x - 3)^2 + y^2 \leq 1$$ Area of shaded region $$= \frac{\pi \cdot 1^2}{4} - \frac{1}{2} \cdot 1 \cdot 1 = \frac{\pi}{4} - \frac{1}{2}$$ Area of unshaded region inside the circle $$= \frac{3}{4} \pi \cdot 1^2 + \frac{1}{2} \cdot 1 \cdot 1 = \frac{3\pi}{4} + \frac{1}{2}$$ Therefore, difference of area $$= \left( \frac{3\pi}{4} + \frac{1}{2} \right) - \left( \frac{\pi}{4} - \frac{1}{2} \right)$$ $$= \frac{\pi}{2} + 1$$

Question 20

Maths · Applications of Integrals · Single correct

The area of the region enclosed by the curves $y = x^2 - 4x + 4$ and $y^2 = 16 - 8x$ is :

  1. $\frac{8}{3}$
  2. $\frac{4}{3}$
  3. 8
  4. 5

Answer: (a)

Solution

Area = $\int$_0^2 $\left$( $\sqrt{16 - 8x}$ - (x^2 - 4x + 4) $\right$) $\,$ dx = $\left$[ $\frac{-(16 - 8x)^{3/2}}{12}$ - $\frac{x^3}{3}$ + 2x^2 + 4x $\right$]_0^2 = $\frac{8}{3}$

Question 21

Maths · Differential Equations · Numerical

Let $y = f(x)$ be the solution of the differential equation $$\frac{dy}{dx} + \frac{xy}{x^2 - 1} = \frac{x^{6+4x}}{\sqrt{1-x^2}}, -1 < x < 1$$ such that $f(0) = 0$. If $6 \int_{-1/2}^{1/2} f(x) \, dx = 2\pi - \alpha$ then $\alpha^2$ is equal to .

Answer: 27

Solution

I.F. $e^{\frac{1}{2} \int \frac{2x}{1-x^2} \, dx} = e^{-\frac{1}{2} \ln(1-x^2)} = \sqrt{1-x^2}$. $y \times \sqrt{1-x^2} = \int (x^6 + 4x) \, dx = \frac{x^7}{7} + 2x^2 + c$. Given $y(0) = 0 \Rightarrow c = 0$. $$y = \frac{\frac{x^7}{7} + 2x^2}{\sqrt{1-x^2}}$$ Now, $6 \int_0^{\frac{\pi}{2}} \frac{x^7}{7} + 2x^2}{\sqrt{1-x^2}} \, dx = 6 \int_0^{\frac{1}{2}} \frac{2x^2}{\sqrt{1-x^2}} \, dx$. $$= 24 \int_0^{\frac{1}{2}} \frac{x^2}{\sqrt{1-x^2}} \, dx$$ Put $x = \sin \theta$, $dx = \cos \theta \, d\theta$. $$= 24 \int_0^{\frac{\pi}{6}} \frac{\sin^2 \theta \cos \theta \, d\theta}{\cos \theta}$$ $$= 24 \int_0^{\frac{\pi}{6}} \left( \frac{1 - \cos 2\theta}{2} \right) \, d\theta = 12 \left[ \theta - \frac{\sin 2\theta}{2} \right]_0^{\frac{\pi}{6}}$$ $$= 12 \left( \frac{\pi}{6} - \frac{\sqrt{3}}{4} \right)$$ $$= 2\pi - 3\sqrt{3}$$ $$\alpha^2 = (3\sqrt{3})^2 = 27$$

Question 22

Maths · Straight Lines and Pair of Straight Lines · Numerical

Let $A(6, 8)$, $B(10 \cos \alpha, -10 \sin \alpha)$ and $C(-10 \sin \alpha, 10 \cos \alpha)$, be the vertices of a triangle. If $L(a, 9)$ and $G(h, k)$ be its orthocenter and centroid respectively, then $(5a - 3h + 6k + 100 \sin 2\alpha)$ is equal to ______.

Answer: 145

Solution

Given the points, we have: $$\frac{a + 0}{3} = h \Rightarrow a = 3h$$ $$\frac{9 + 0}{3} = k \Rightarrow k = 3$$ Therefore, $$(h, k) = \left( \frac{6 + 10 \cos \alpha - 10 \sin \alpha}{3}, \frac{8 - 10 \sin \alpha + 10 \cos \alpha}{3} \right)$$ From the equations: $$6 + 10 \cos \alpha - 10 \sin \alpha = 3h$$ $$10 \cos \alpha - 10 \sin \alpha = 3h - 6$$ $$10(\cos \alpha - \sin \alpha) = 1$$ And, $$\frac{8 - 10 \sin \alpha + 10 \cos \alpha}{3} = k$$ Solving further: $$\Rightarrow 100 \sin 2\alpha = 99$$ $$h = \frac{7}{3}$$ $$\Rightarrow a = 7$$ Now, $$5a - 3h + 6k + 100 \sin 2\alpha = 35 - 7 + 18 + 99 = 145$$

Question 23

Maths · Three Dimensional Geometry · Numerical

Let the distance between two parallel lines be $5$ units and a point $P$ lie between the lines at a unit distance from one of them. An equilateral triangle $PQR$ is formed such that $Q$ lies on one of the parallel lines, while $R$ lies on the other. Then $(QR)^2$ is equal to _______.

Answer: 28

Solution

Given $PR = \csc \theta$, $PQ = 4 \sec(30^\circ + \theta)$. For equilateral $d = PR = PQ$. Therefore, $$\cos(\theta + 30^\circ) = 4 \sin \theta$$ which implies $$\frac{\sqrt{3}}{2} \cos \theta - \frac{1}{2} \sin \theta = 4 \sin \theta$$ leading to $$\tan \theta = \frac{1}{3\sqrt{3}}.$$ Thus, $$QR^2 = d^2 = \csc^2 \theta = 28.$$

Question 24

Maths · Binomial Theorem · Fill in the blank

If $\sum$_{r=1}^{30} $\frac{r^2 \left(^{30}C_r\right)^2}{^{30}C_{r-1}}$ = $\alpha$ $\times$ 2^{29}, then $\alpha$ is equal to

Answer: 465

Solution

Given the expression $$\sum_{r=1}^{30} r^2 \left( \binom{30}{r} \right)^2$$ we start by rewriting it as $$\sum_{r=1}^{30} r^2 \left( \frac{31-r}{r} \right) \cdot \frac{30!}{r!(30-r)!}$$ which simplifies to $$\sum_{r=1}^{30} \frac{(31-r)!}{(r-1)!(30-r)!}$$ This can be rewritten as $$30 \sum_{r=1}^{30} \frac{(31-r)29!}{(r-1)!(30-r)!}$$ which simplifies further to $$30 \sum_{r=1}^{30} (30-r+1) \binom{30}{30-r}$$ This is equal to $$30 \left( \sum_{r=1}^{30} (31-r) \binom{30}{30-r} + \sum_{r=1}^{30} \binom{30}{30-r} \right)$$ which simplifies to $$30 (29 \times 2^{28} + 2^{29}) = 30(29+2)2^{28}$$ Simplifying further, we have $$= 15 \times 31 \times 2^{29}$$ which equals $$= 465 \times 2^{29}$$ Therefore, $$\alpha = 465$$

Question 25

Maths · Sets · Numerical

Let $A = \{1, 2, 3\}$. The number of relations on $A$, containing $(1, 2)$ and $(2, 3)$, which are reflexive and transitive but not symmetric, is

Answer: 3

Solution

Given $R$ is reflexive $\Rightarrow R$ have $(1,1), (2,2), (3,3)$. $R$ is transitive. Since $(1,2), (2,3) \in R$ and $(1,3) \in R$, therefore, $R_1 = \{(1,1), (2,2), (3,3), (1,2), (2,3), (1,3)\}$. Clearly $R_1$ is reflexive and transitive but not symmetric. Similarly, $R_2 = \{(1,1), (2,2), (3,3), (1,2), (2,3), (1,3), (3,2)\}$ and $R_3 = \{(1,1), (2,2), (3,3), (1,2), (2,3), (1,3), (2,1)\}$. Therefore, 3 relations are possible.

Physics

Question 26

Physics · Ray Optics and Optical Instruments · Single correct

A symmetric thin biconvex lens is cut into four equal parts by two planes $AB$ and $CD$ as shown in figure. If the power of original lens is $4 \, \mathrm{D}$ then the power of a part of the divided lens is

  1. $\mathrm{D}$
  2. $8 \, \mathrm{D}$
  3. $2 \, \mathrm{D}$
  4. $4 \, \mathrm{D}$

Answer: (c)

Solution

For the first lens, $$\frac{1}{f_1} = (\mu - 1) \frac{2}{R} = P = 4D$$. For the second lens, $$\frac{1}{f_2} = (\mu - 1) \frac{1}{R} = \frac{P}{2} = 2D$$.

Question 27

Physics · Mechanical Properties of Fluids · Single correct

A small rigid spherical ball of mass $M$ is dropped in a long vertical tube containing glycerine. The velocity of the ball becomes constant after some time. If the density of glycerine is half of the density of the ball, then the viscous force acting on the ball will be (consider $g$ as acceleration due to gravity)

  1. $2 \, Mg$
  2. $Mg$
  3. $\frac{3}{2} Mg$
  4. $\frac{Mg}{2}$

Answer: (d)

Solution

Given the forces acting on the object, we have the equation: $$mg - F_B - f = 0$$ Substituting for $F_B$, we get: $$mg - \frac{mg}{2} - f = 0$$ Therefore, $$f = \frac{mg}{2}$$

Question 28

Physics · Physical World, Units and Measurements · Single correct

The maximum percentage error in the measurment of density of a wire is [Given, mass of wire = $(0.60 \pm 0.003)\, \mathrm{g}$ radius of wire = $(0.50 \pm 0.01)\, \mathrm{cm}$ length of wire = $(10.00 \pm 0.05)\, \mathrm{cm}$]

  1. 8
  2. 5
  3. 4
  4. 7

Answer: (b)

Solution

Given $d = \frac{m}{vol.} = \frac{m}{\pi R^2 \ell}$, we have $\frac{d\rho}{\rho} = \frac{dm}{m} + \frac{2 \, dR}{R} + \frac{d\ell}{\ell}$. Therefore, $$\frac{d\rho}{\rho} = \left( \frac{0.003}{0.6} + \frac{2 \times 0.01}{0.5} + \frac{0.05}{10} \right) 100 = 5\%$$

Question 29

Physics · Alternating Current · Single correct

A series LCR circuit is connected to an alternating source of emf E. The current amplitude at resonant frequency is $I_0$. If the value of resistance R becomes twice of its initial value then amplitude of current at resonance will be

  1. 2I_0
  2. I_0
  3. $\frac{I_0}{2}$
  4. $\frac{I_0}{\sqrt{2}}$

Answer: (c)

Solution

Initially, $I_0 = \frac{\varepsilon_m}{R}$. Finally, $I_0^1 = \frac{\varepsilon_m}{2R} = \frac{I_0}{2}$.

Question 30

Physics · Electric Charges and Fields · Single correct

For a short dipole placed at origin $O$, the dipole moment $P$ is along $x$-axis, as shown in the figure. If the electric potential and electric field at $A$ are $V_0$ and $E_0$, respectively, then the correct combination of the electric potential and electric field, respectively, at point $B$ on the $y$-axis is given by

  1. $V_0$ and $\frac{E_0}{4}$
  2. zero and $\frac{E_0}{16}$
  3. zero and $\frac{E_0}{8}$
  4. $\frac{V_0}{2}$ and $\frac{E_0}{16}$

Answer: (b)

Solution

Given: - The electric potential of A is $V_0$ - The electric field of A is $E_0$. We need to determine the electric potential and electric field at point 8. Step E1: Electric Potential of a Dipole The electric potential $V$ due to a short dipole at a point at distance $r$ is: $$V = \frac{1}{4\pi\varepsilon_0} \cdot \frac{pr^2}{r^2}$$ On the axial line (Point A at distance $r$): On the equatorial line (Point B at distance $2r$): Since the dipole potential is given by: $$V_A = \frac{1}{4\pi\varepsilon_0} \cdot \frac{p}{r^2} = V_0$$ $$V = \frac{1}{4\pi\varepsilon_0} \cdot \frac{p \cos \theta}{r^2}$$ and on the equatorial line $\theta = 90^\circ \Rightarrow \cos 90^\circ = 0$, $$V_g = 0$$ Thus, the electric potential at 8 is zero. Step 2: Electric Field of a Dipole The magnitude of the electric field at a distance $r$ from a dipole: On the axial line: $$B_{axial} = \frac{1}{4\pi\varepsilon_0} \cdot \frac{2p}{r^3}$$ Given that of A (on the axial line of $r$), the field is $E_0$: $$E_A = E_n = \frac{1}{4\pi\varepsilon_0} \cdot \frac{2p}{r_1^3}$$ On the equatorial line: $$E_{equatorial} = \frac{1}{4\pi\varepsilon_0} \cdot \frac{p}{r^3}$$ At B (distance $2r$): $$E_8 = \frac{1}{4\pi\varepsilon_0} \cdot \frac{p}{(2r)^3} = \frac{1}{4\pi\varepsilon_0} \cdot \frac{p}{6r^3}$$ Since $E_0 = \frac{1}{4\pi\varepsilon_0} \cdot \frac{2p}{r^3}$, we can express $E_n$ in terms of $E_0$: $$E_n = \frac{E_0}{16}$$ Final Answer: - Electric potential at E = 0 - Electric field to B = $\frac{E_0}{10}$

Question 31

Physics · Electrostatic Potential and Capacitance · Single correct

Which one of the following is the correct dimensional formula for the capacitance in F? M, L, T and C stand for unit of mass, length, time and charge,

  1. [F] = \left[ C^2 M^{-1} L^{-2} T^2 \right]
  2. [F] = \left[ C^2 M^{-2} L^2 T^2 \right]
  3. [F] = \left[ C M^{-2} L^{-2} T^{-2} \right]
  4. [F] = \left[ C M^{-1} L^{-2} T^2 \right]

Answer: (a)

Solution

Energy is given by $$\frac{Q^2}{2C}$$. Therefore, the dimensional formula for $$[F]$$ is $$[C^2]$$ which is $$[ML^2T^{-2}]$$. This simplifies to $$[C^2M^{-1}L^{-2}T^{+2}]$$.

Question 32

Physics · Moving Charges and Magnetism · Single correct

An electron projected perpendicular to a uniform magnetic field B moves in a circle. If Bohr's quantization is applicable, then the radius of the electronic orbit in the first excited state is:

  1. $\sqrt{\frac{h}{\pi e B}}$
  2. $\sqrt{\frac{2h}{\pi e B}}$
  3. $\sqrt{\frac{h}{2\pi e B}}$
  4. $\sqrt{\frac{4h}{\pi e B}}$

Answer: (a)

Solution

Given $$mvr = \frac{nh}{2\pi} ...(i)$$ $$r = \frac{vm}{Bq} ...(ii)$$ Let $\($ n = 2 $\)$. Then $$mr \left( \frac{rBq}{m} \right) = \frac{2h}{2\pi}$$ Solving for $\($ r $\)$, we get $$r = \sqrt{\frac{h}{\pi Bq}}$$ Given $\($ q = e $\)$, we have $$r = \sqrt{\frac{h}{\pi Be}}$$

Question 33

Physics · Kinetic Theory · Single correct

For a diatomic gas, if $\gamma_1 = \left( \frac{C_p}{C_v} \right)$ for rigid molecules and $\gamma_2 = \left( \frac{C_p}{C_v} \right)$ for another diatomic molecules, but also having vibrational modes. Then, which one of the following options is correct? (Cp and Cv are specific heats of the gas at constant pressure and volume)

  1. $\gamma_2 = \gamma_1$
  2. $2\gamma_2 = \gamma_1$
  3. $\gamma_2 < \gamma_1$
  4. $\gamma_2 > \gamma_1$

Answer: (c)

Solution

For rigid diatomic molecules $$f = 5$$ $$\therefore \gamma_1 = \frac{7}{5} = 1.4$$ For non-rigid diatomic molecules $$f = 5 + 2 = 7$$ $$\gamma_2 = \frac{9}{7} = 1.28$$ $$\therefore \gamma_1 > \gamma_2$$

Question 34

Physics · Electromagnetic Induction · Single correct

A rectangular metallic loop is moving out of a uniform magnetic field region to a field free region with a constant speed. When the loop is partially inside the magnetic field, the plot of magnitude of induced emf ($\varepsilon$) with time ($t$) is given by

Answer: (d)

Solution

The electromotive force is given by the negative rate of change of magnetic flux. $$E = -\frac{d\phi}{dt}$$ The magnetic flux is given by $$\phi = Bbx$$ The magnitude of the electromotive force is $$|E| = Bbv$$

Question 35

Physics · Dual Nature of Radiation and Matter · Single correct

A light source of wavelength $\lambda$ illuminates a metal surface and electrons are ejected with maximum kinetic energy of $2 \, \mathrm{eV}$. If the same surface is illuminated by a light source of wavelength $\frac{\lambda}{2}$, then the maximum kinetic energy of ejected electrons will be (The work function of metal is $1 \, \mathrm{eV}$)

  1. $3 \, \mathrm{eV}$
  2. $2 \, \mathrm{eV}$
  3. $6 \, \mathrm{eV}$
  4. $5 \, \mathrm{eV}$

Answer: (d)

Solution

Einstein's photoelectric equation $$KE = \frac{hc}{\lambda} = \phi_0$$ $$2 \, eV = \frac{hc}{\lambda} - 1 \, eV$$ $$\frac{hc}{\lambda} = 3 \, eV$$ $$KE' = \frac{hc}{(\lambda/2)} - \phi_0 = 6 \, eV - 1 \, eV$$ $$= 5 \, eV$$

Question 36

Physics · Gravitation · Single correct

Given below are two statements. One is labelled as Assertion (A) and the other is labelled as Reason (R). Assertion (A): A simple pendulum is taken to a planet of mass and radius, 4 times and 2 times, respectively, than the Earth. The time period of the pendulum remains same on earth and the planet. Reason (R): The mass of the pendulum remains unchanged at Earth and the other planet. In the light of the above statements, choose the correct answer from the options given below:

  1. is false but (R) is true
  2. is true but (R) is false
  3. Both (A) and (R) are true and (R) is the correct explanation of (A)
  4. Both (A) and (R) are true but (R) is NOT the correct explanation of (A)

Answer: (d)

Solution

Given $g = \frac{GM}{R^2}$. $$g' = \frac{G(4M)}{(2R)^2} = g$$ A is correct, $R$ is correct; but since $T = 2\pi \sqrt{\frac{\ell}{g}}$ doesn't depend on mass; $R$ doesn't explain A.

Question 37

Physics · System of Particles and Rotational Motion · Single correct

The torque due to the force $(2\hat{i} + \hat{j} + 2\hat{k})$ about the origin, acting on a particle whose position vector is $(\hat{i} + \hat{j} + \hat{k})$, would be

  1. $\hat{i} - \hat{k}$
  2. $\hat{i} + \hat{k}$
  3. $\hat{j} + \hat{k}$
  4. $\hat{i} - \hat{j} + \hat{k}$

Answer: (a)

Solution

Given $\tau = \mathbf{r} \times \mathbf{F}$. $$\tau = \begin{vmatrix} \hat{i} & \hat{j} & \hat{k} \\ 1 & 1 & 1 \\ 2 & 1 & 2 \end{vmatrix}$$ $$\tau = \hat{i}(2 - 1) - \hat{j}[0] + \hat{k}(1 - 2)$$ $$= \hat{i} - \hat{k}$$

Question 38

Physics · Semiconductor Electronics: Materials, Devices and Simple Circuits · Single correct

\begin{tabular}{|c|c|c|} \hline A & B & Y \\ \hline 0 & 0 & 1 \\ \hline 0 & 1 & 1 \\ \hline 1 & 0 & 0 \\ \hline 1 & 1 & 1 \\ \hline \end{tabular} To obtain the given truth table, following logic gate should be placed at G:

  1. OR Gate
  2. AND Gate
  3. NOR Gate
  4. NAND Gate

Answer: (c)

Solution

$\therefore$ Truth table \begin{tabular}{|c|c|c|} \hline A & B & Y \\ \hline 0 & 0 & 1 \\ \hline 0 & 1 & 1 \\ \hline 1 & 0 & 0 \\ \hline 1 & 1 & 1 \\ \hline \end{tabular} For NOR gate: $\overline{AB} = \overrightarrow{A + B}$.

Question 39

Physics · Work, Energy and Power · Single correct

A force $\vec{F} = 2\hat{i} + b\hat{j} + \hat{k}$ is applied on a particle and it undergoes a displacement $\hat{i} - 2\hat{j} - \hat{k}$. What will be the value of $b$, if work done on the particle is zero.

  1. 0
  2. $\frac{1}{2}$
  3. 2
  4. $\frac{1}{3}$

Answer: (b)

Solution

Given $w = 0$. Therefore, $\vec{F} \cdot S = 0$. $$(2\hat{i} + b\hat{j} + \hat{k}) \cdot (\hat{i} - 2\hat{j} - \hat{k}) = 0$$ $$2 - 2b - 1 = 0$$ $$b = \frac{1}{2}$$

Question 40

Physics · Wave Optics · Single correct

Given below are two statements. One is labelled as Assertion (A) and the other is labelled as Reason (R). Assertion (A) : In Young's double slit experiment, the fringes produced by red light are closer as compared to those produced by blue light. Reason (R): The fringe width is directly proportional to the wavelength of light. In the light of the above statements, choose the correct answer from the options given below :

  1. Both (A) and (R) are true but (R) is NOT the correct explanation of (A)
  2. is true but (R) is false
  3. Both (A) and (R) are true and (R) is the correct explanation of (A)
  4. is false but (R) is true

Answer: (d)

Solution

Given $\beta = \frac{\lambda D}{d}$. We have $\lambda_{red} > \lambda_{blue}$. Assertion is false. Reason is true.

Question 41

Physics · Motion in a Plane · Single correct

A ball of mass 100 g is projected with velocity 20 m/s at $60^\circ$ with horizontal. The decrease in kinetic energy of the ball during the motion from point of projection to highest point is

  1. 5 J
  2. 15 J
  3. 20 J
  4. zero

Answer: (b)

Solution

The initial kinetic energy $k_i$ is given by $$k_i = \frac{1}{2} mv^2.$$ The final kinetic energy $k_f$ is given by $$k_f = \frac{1}{2} m (v \cos 60^\circ)^2 = \frac{1}{8} mv^2.$$ The change in kinetic energy $\Delta k$ is $$\Delta k = k_i - k_f = \frac{3}{8} mv^2 = \frac{3}{8} \times 0.1 \times 400 = 15 \, \mathrm{J}.$$

Question 42

Physics · Ray Optics and Optical Instruments · Single correct

A transparent film of refractive index, 2.0 is coated on a glass slab of refractive index, 1.45. What is the minimum thickness of transparent film to be coated for the maximum transmission of Green light of wavelength 550 nm. [Assume that the light is incident nearly perpendicular to the glass surface.]

  1. 137.5 nm
  2. 275 nm
  3. 94.8 nm
  4. 68.7 nm

Answer: (a)

Solution

For transmitted green light to be maxima, reflected green should be minima. $$\Delta P = 2 \mu_0 t = n \lambda$$ $$\Rightarrow t = \frac{n \lambda}{2 \mu_0} \therefore t_{\min} = \frac{\lambda}{2 \mu_0} = \frac{550}{2 \times 2} = 137.5$$

Question 43

Physics · Mechanical Properties of Fluids · Single correct

A tube of length $L$ is shown in the figure. The radius of cross section at the point (1) is $2 \, \mathrm{cm}$ and at the point (2) is $1 \, \mathrm{cm}$, respectively. If the velocity of water entering at point (1) is $2 \, \mathrm{m/s}$, then velocity of water leaving the point (2) will be

  1. $4 \, \mathrm{m/s}$
  2. $2 \, \mathrm{m/s}$
  3. $6 \, \mathrm{m/s}$
  4. $8 \, \mathrm{m/s}$

Answer: (d)

Solution

Given $A_1 V_1 = A_2 V_2$. Therefore, $2\pi (2R)^2 = V_2 \pi R^2$. Thus, $V_2 = 8 \, \mathrm{m/s}$.

Question 44

Physics · Kinetic Theory · Single correct

Given are statements for certain thermodynamic variables, (A) Internal energy, volume (V) and mass (M) are extensive variables. (B) Pressure (P), temperature (T) and density ($\rho$) are intensive variables. (C) Volume (V), temperature (T) and density ($\rho$) are intensive variables. (D) Mass (M), temperature (T) and internal energy are extensive variables. Choose the correct answer from the options given below:

  1. and (C) Only
  2. and (D) Only
  3. and (A) Only
  4. and (B) Only

Answer: (d)

Solution

Extensive variables depend on size and amount of system. Extensive: Volume, mass, internal energy. Intensive: Pressure, temperature, density.

Question 45

Physics · Work, Energy and Power · Single correct

A body of mass 100 g is moving in circular path of radius 2 m on vertical plane as shown in figure. The velocity of the body at point $A$ is 10 m/s. The ratio of its kinetic energies at point $B$ and $C$ is: (Take acceleration due to gravity as 10 m/$s^2$)

  1. $\frac{2+\sqrt{2}}{3}$
  2. $\frac{2+\sqrt{3}}{3}$
  3. $\frac{3+\sqrt{3}}{2}$
  4. $\frac{3-\sqrt{2}}{2}$

Answer: (c)

Solution

Given the equation: $\($ $\frac{1}{2}$ m $\times$ 100 + 0 = $\frac{1}{2}$ m V_B^2 + mg $\left$( R - $\frac{R \sqrt{3}}{2}$ $\right$) $\)$. Solving for $\($ V_B^2 $\)$: $\[$ 100 = V_B^2 + 2gR $\left$( 1 - $\frac{\sqrt{3}}{2}$ $\right$) $\]$ $\[$ V_B^2 = 100 - 20(2 - $\sqrt{3}$) $\]$ $\[$ V_B^2 = 60 + 20 $\sqrt{3}$ $\]$ The kinetic energy at point B is: $\[$ K.E_B = $\frac{1}{2}$ m V_B^2 = $\frac{m}{2}$ (60 + 20 $\sqrt{3}$) $\]$ For point C: $\[$ $\frac{1}{2}$ m (100) = $\frac{1}{2}$ m V $\]$ $\[$ 100 = mg $\left$( $\frac{3R}{2}$ $\right$) $\]$ $\[$ 100 V_C^2 = 60 $\]$ $\[$ V_C^2 = 40 $\]$ The kinetic energy at point C is: $\[$ K.E_C = $\frac{1}{2}$ m V V_C^2 = $\frac{1}{2}$ m (40) $\]$ Comparing kinetic energies: $\[$ $\frac{60 + 20 \sqrt{3}}{40}$ = $\frac{3}{2}$ + $\frac{\sqrt{3}}{2}$ = $\frac{3 + \sqrt{3}}{2}$ $\]$

Question 46

Physics · Moving Charges and Magnetism · Numerical

A proton is moving undeflected in a region of crossed electric and magnetic fields at a constant speed of $2 \times 10^5 \, \mathrm{ms}^{-1}$. When the electric field is switched off, the proton moves along a circular path of radius $2 \, \mathrm{cm}$. The magnitude of electric field is $x \times 10^4 \, \mathrm{N/C}$. The value of $x$ is . Take the mass of the proton $= 1.6 \times 10^{-27} \, \mathrm{kg}$.

Answer: 2

Solution

Given $Bvq = Eq$ and $E = Bv$. We have $vm = Bq$ and $r = \frac{Bq}{mv}$. Therefore, $B = \frac{mv}{rq}$. Now, $E = \left(\frac{mv}{rq}\right)v = \frac{mv^2}{rq}$. Calculating, $$1.6 \times 10^{-27} \times 4 \times 10^{10}$$ $$= \frac{2 \times 10^{-2} \times 1.6 \times 10^{-19}}{2 \times 10^4 \, \mathrm{N/C}}$$ Finally, $x = 2$.

Question 47

Physics · Moving Charges and Magnetism · Numerical

Two long parallel wires $X$ and $Y$, separated by a distance of $6 \, \mathrm{cm}$, carry currents of $5 \, \mathrm{A}$ and $4 \, \mathrm{A}$, respectively, in opposite directions as shown in the figure. Magnitude of the resultant magnetic field at point $P$ at a distance of $4 \, \mathrm{cm}$ from wire $Y$ is $x \times 10^{-5} \, \mathrm{T}$. The value of $x$ is__________. Take permeability of free space as $\mu_0 = 4\pi \times 10^{-7} \, \mathrm{SI}$ units.

Answer: 1

Solution

The magnetic field at point P due to the current in wire X is given by: $$B_X = \frac{\mu_0 (5)}{2\pi \times 0.01}$$ The magnetic field at point P due to the current in wire Y is given by: $$B_Y = \frac{\mu_0 (4)}{2\pi \times 0.04}$$ The net magnetic field at point P is: $$B = B_X - B_Y$$ Substituting the values, we get: $$B = \frac{\mu_0 (5)}{2\pi \times 0.01} - \frac{\mu_0 (4)}{2\pi \times 0.04}$$ Simplifying, we have: $$B = \frac{100 \mu_0}{4\pi}$$ $$B = -100 \times 10^{-7}$$ $$B = -1 \times 10^{-5} \, \mathrm{T}$$

Question 48

Physics · Electromagnetic Waves · Numerical

A parallel plate capacitor of area $A = 16 \, \mathrm{cm}^2$ and separation between the plates $10 \, \mathrm{cm}$, is charged by a DC current. Consider a hypothetical plane surface of area $A_0 = 3.2 \, \mathrm{cm}^2$ inside the capacitor and parallel to the plates. At an instant, the current through the circuit is $6 \, \mathrm{A}$. At the same instant the displacement current through $A_0$ is ____ mA.

Answer: 1200

Solution

Given $i_d = i_c$. Total displacement current $= 6 \, \mathrm{A}$. Through $A_0$, $$i = \left( \frac{A_0}{A} \right) 6$$ $$= \frac{3.2}{16} \times 6 = 1.2 \, \mathrm{A} = 1200 \, \mathrm{mA}$$

Question 49

Physics · System of Particles and Rotational Motion · Numerical

A tube of length 1 m is filled completely with an ideal liquid of mass 2 M, and closed at both ends. The tube is rotated uniformly in horizontal plane about one of its ends. If the force exerted by the liquid at the other end is F then angular velocity of the tube is $\sqrt{\frac{F}{\alpha M}}$ in SI unit. The value of $\alpha$ is _________.

Answer: 1

Solution

Step 1: Consider the Force at a Distance $x$. When the tube rotates with angular velocity $\omega$, each element of the liquid experiences a centrifugal force. The force at a distance $x$ from the pivot can be found by considering the differential force due to an element of liquid. $$dF = \rho A dx \omega^2 x$$ where $\rho$ is the volumetric mass density of the liquid. Step 2: Find the Volumetric Mass Density. Since the mass of the liquid is $2M$, the length of the tube is $1 \, \mathrm{m}$, and let the area of cross-section is $A$, the volumetric mass density is: $$\rho = \frac{2M}{AL} = \frac{2M}{A}$$ Step 3: Calculate the Total Force at the Other End. The force at $x = L$ is obtained by integrating: $$F = \int_0^L \rho x \omega^2 dx$$ $$F = 2M \omega^2 \int_0^1 x dx$$ $$F = \frac{2M \omega^2}{2} = M \omega^2$$ Step 4: Solve for $\omega$. $$\omega^2 = \frac{F}{M}$$ $$\omega = \sqrt{\frac{F}{M}}$$

Question 50

Physics · Current Electricity · Numerical

The net current flowing in the given circuit is ______ A.

Answer: 1

Solution

The equivalent resistance $R_{eq} = 2 \, \Omega$. The current $I = \frac{2}{2} = 1 \, A$.

Chemistry

Question 51

Chemistry · Chemical Bonding and Molecular Structure · Single correct

Arrange the following compounds in increasing order of their dipole moment: HBr, $H_2 S$, $NF_3$ and $CHCl_3$

  1. $H_2 S < HBr < NF_3 < CHCl_3$
  2. $NF_3 < HBr < H_2 S < CHCl_3$
  3. $HBr < H_2 S < NF_3 < CHCl_3$
  4. $CHCl_3 < NF_3 < HBr < H_2 S$

Answer: (b)

Solution

Given $\mu_{\mathrm{HBr}} = 0.78 \, \mathrm{D}$, $\mu_{\mathrm{H_2 S}} = 0.95 \, \mathrm{D}$, $\mu_{\mathrm{NF_3}} = 0.24 \, \mathrm{D}$, $\mu_{\mathrm{CHCl_3}} = 1.01 \, \mathrm{D}$. Hence dipole moment of $\mathrm{NF_3} < \mathrm{HBr} < \mathrm{H_2 S} < \mathrm{CHCl_3}$.

Question 52

Chemistry · Biomolecules · Single correct

Identify the number of structure/s from the following which can be correlated to D-glyceraldehyde.

  1. four
  2. one
  3. two
  4. three

Answer: (d)

Solution

In A, B, D - OH group in right hand side then D-configuration is assigned.

Question 53

Chemistry · The p-Block Elements (Group 15, 16, 17 & 18) · Single correct

The maximum covalency of a non-metallic group 15 element ' E ' with weakest $E - E$ bond is :

  1. 4
  2. 6
  3. 3
  4. 5

Answer: (a)

Solution

N - N < P - P: single ($\sigma$) bond strength. Due to L.P.-L.P. repulsion and maximum possible covalency of nitrogen is 4.

Question 54

Chemistry · Chemical Kinetics and Nuclear Chemistry · Single correct

Consider the given figure and choose the correct option:

  1. Activation energy of both forward and backward reaction is $E_1 + E_2$ and reactant is more stable than product.
  2. Activation energy of forward reaction is $E_1 + E_2$ and product is less stable than reactant.
  3. Activation energy of backward reaction is $E_1$ and product is more stable than reactant.
  4. Activation energy of forward reaction is $E_1 + E_2$ and product is more stable than reactant.

Answer: (b)

Solution

Activation energy of forward reaction is given by $E_1 + E_2$. The energy of the product is greater than the energy of the reactant. Stability is such that reactant is greater than product.

Question 55

Chemistry · Haloalkanes and Haloarenes · Single correct

When sec-butylcyclohexane reacts with bromine in the presence of sunlight, the major product is :

Answer: (c)

Solution

Formation of more stable free radical intermediate.

Question 56

Chemistry · Redox Reactions · Single correct

The species which does not undergo disproportionation reaction is:

  1. $\mathrm{ClO}_3^-$
  2. $\mathrm{ClO}^-$
  3. $\mathrm{ClO}_2^-$
  4. $\mathrm{ClO}_4^-$

Answer: (b)

Solution

Given $\mathrm{ClO_4^-} \rightarrow x + \{(-2) \times 4\} = -1 \Rightarrow x = +7$. Chlorine is in its maximum oxidation state, so disproportionation not possible in $\mathrm{ClO_4^-}$.

Question 57

Chemistry · Amines · Single correct

Match the Compounds (List - I) with the appropriate Catalyst/Reagents (List - II) for their reduction into corresponding amines.

  1. (A)-(II), (B)-(I), (C)-(III), (D)-(IV)
  2. (A)-(III), (B)-(II), (C)-(IV), (D)-(I)
  3. (A)-(II), (B)-(IV), (C)-(III), (D)-(I)
  4. (A)-(III), (B)-(IV), (C)-(II), (D)-(I)

Answer: (d)

Solution

Option (A) involves the reduction of an amide to an amine using $\mathrm{LiAlH_4}$ and $\mathrm{H_2O}$. Option (B) involves the reduction of a nitro group to an amine using $\mathrm{Sn}$ and $\mathrm{HCl}$. Option (C) involves the reduction of a nitrile to an amine using $\mathrm{H_2/Ni}$. Option (D) involves the hydrolysis of a cyclic imide to a dicarboxylate salt using $\mathrm{aq.\ NaOH}$.

Question 58

Chemistry · Haloalkanes and Haloarenes · Single correct

The maximum number of RBr producing 2-methylbutane by above sequence of reactions is ________ - (Consider the structural isomers only)

  1. 5
  2. 4
  3. 3
  4. 1

Answer: (b)

Solution

$RBr \xrightarrow[\text{dry Ether}]{Mg} RMgBr \xrightarrow{H_2O} R-H$ Hence, RBr can be Total 4 structural isomers

Question 59

Chemistry · Thermodynamics · Single correct

\textbf{Match List–I with List–II} \begin{tabular}{|c|c|} \hline \textbf{List–I (Partial Derivatives)} & \textbf{List–II (Thermodynamic Quantities)} \\ \hline (A) $\left( \dfrac{\partial G}{\partial T} \right)_P$ & (I) $C_P$ \\ (B) $\left( \dfrac{\partial H}{\partial T} \right)_P$ & (II) $-S$ \\ (C) $\left( \dfrac{\partial G}{\partial P} \right)_T$ & (III) $C_V$ \\ (D) $\left( \dfrac{\partial U}{\partial T} \right)_V$ & (IV) $V$ \\ \hline \end{tabular} \textbf{Choose the correct answer from the options given below.}

  1. (A)-(II), (B)-(I), (C)-(III), (D)-(IV)
  2. (A)-(I), (B)-(II), (C)-(IV), (D)-(III)
  3. (A)-(II), (B)-(I), (C)-(IV), (D)-(III)
  4. (A)-(II), (B)-(III), (C)-(I), (D)-(IV)

Answer: (c)

Solution

Since $dH = dq$ (at $P = constant$), $$dH = C_p dT$$ $$\left( \frac{dH}{dT} \right)_P = C_P$$ $dU = dq$ (at $V = constant$), $$dU = C_v dT$$ $$\left( \frac{dU}{dT} \right)_V = C_V$$ Since $dG = VdP - SdT$, at $P = constant$, $dP = 0$, $$\left( \frac{dG}{dT} \right)_P = -S$$ at $T = constant$, $$\left( \frac{dG}{dP} \right)_T = V$$

Question 60

Chemistry · Co-ordination Compounds · Single correct

The correct order of the following complexes in terms of their crystal field stabilization energies is :

  1. [Co(NH_3)_4]^{2+} < [Co(NH_3)_6]^{2+} < [Co(en)_3]^{3+} < [Co(NH_3)_6]^{3+}
  2. [Co(NH_3)_6]^{2+} < [Co(NH_3)_4]^{2+} < [Co(en)_3]^{3+}
  3. [Co(en)_3]^{3+} < [Co(NH_3)_6]^{3+} < [Co(NH_3)_4]^{2+}
  4. [Co(NH_3)_4]^{2+} < [Co(NH_3)_6]^{3+} < [Co(en)_3]^{3+}

Answer: (d)

Solution

Crystal field splitting energy ($\Delta$) is proportional to the charge or oxidation state of the central metal atom. Crystal field splitting energy ($\Delta$) is also proportional to the field strength of the ligand (and chelation). Crystal field stabilisation energy (CFSE) is given by: $$\left[-0.4 t_{2g} + 0.6 eg \right] \Delta_\circ (for octahedral)$$ For, $$[Co(en)_3]^{3+} : Co^{3+} : t_{2g}^6 e_g^0; CFSE = -2.4(\Delta_0)_1$$ $$[Co(NH_3)_6]^{3+} : Co^{3+} : t_{2g}^6 e_g^0; CFSE = -2.4(\Delta_0)_2$$ $$[Co(NH_3)_6]^{2+} : Co^{2+} : t_{2g}^5 e_g^2; CFSE = -0.8(\Delta_0)_3$$ $$[Co(NH_3)_4]^{2+} : Co^{2+} : e_g^4 t_{2g}^2; CFSE = -1.2\Delta_t$$ As: $$\left(\Delta_t = \frac{4}{9}(\Delta_0)_3\right)$$ Therefore, $$\Delta_t < (\Delta_0)_3 < (\Delta_0)_2 < (\Delta_0)_1$$

Question 61

Chemistry · Solutions · Single correct

Density of 3 M NaCl solution is 1.25 $\mathrm{g/mL}$. The molality of the solution is :

  1. 1.79 $\,$ $\mathrm{m}$
  2. 2.79 $\,$ $\mathrm{m}$
  3. 2 $\,$ $\mathrm{m}$
  4. 3 $\,$ $\mathrm{m}$

Answer: (b)

Solution

Given $3M \mathrm{NaCl}$, $d_{sol} = 1.25 \, \mathrm{gm/mol}$. Molality $= \frac{M \times 1000}{1000 \, d - M \times M_W}$ $$= \frac{3000}{1250 - 175.5} = 2.79$$

Question 62

Chemistry · Equilibrium · Single correct

The molar solubility(s) of zirconium phosphate with molecular formula $\left( \mathrm{Zr}^{4+} \right)_3 \left( \mathrm{PO}_4^{3-} \right)_4$ is given by relation:

  1. $\left( \frac{K_{\mathrm{sp}}}{9612} \right)^{\frac{1}{3}}$
  2. $\left( \frac{K_{\mathrm{sp}}}{6912} \right)^{\frac{1}{7}}$
  3. $\left( \frac{K_{\mathrm{sp}}}{8435} \right)^{\frac{1}{7}}$
  4. $\left( \frac{K_{\mathrm{sp}}}{5348} \right)^{\frac{1}{6}}$

Answer: (b)

Solution

The dissolution reaction is given by: $$\mathrm{Zr_3(PO_4)_4 (s) \rightleftharpoons 3Zr^{+4} (aq) + 4PO_4^{-3} (aq)}$$ Let the solubility be $s$. The solubility product $K_{sp}$ is given by: $$K_{sp} = (3s)^3 (4s)^4 = 6912 \, s^7$$ Solving for $s$: $$s = \left( \frac{K_{sp}}{6912} \right)^{1/7}$$

Question 63

Chemistry · Organic Chemistry — Some Basic Principles & Techniques · Single correct

The most stable carbocation from the following is :

Answer: (c)

Solution

Due to the +M effect of -OMe at the para position, it will be most stable among these.

Question 64

Chemistry · Classification of Elements and Periodicity in Properties · Single correct

Given below are two statements: Statement (I): An element in the extreme left of the periodic table forms acidic oxides. Statement (II): Acid is formed during the reaction between water and oxide of a reactive element present in the extreme right of the periodic table. In the light of the above statements, choose the correct answer from the options given below:

  1. Statement I is true but Statement II is false
  2. Both Statement I and Statement II are true
  3. Both Statement I and Statement II are false
  4. Statement I is false but Statement II is true

Answer: (d)

Solution

Analyzing Statement (I) The extreme left of the periodic table corresponds to the alkali metals (Group 1) and alkaline earth metals (Group 2). These metals typically form basic (or occasionally amphoteric, in the case of some Group 2 elements) oxides, not acidic oxides. For example, $\mathrm{Na_2O}$, $\mathrm{K_2O}$, $\mathrm{MgO}$, $\mathrm{CaO}$, etc., all form basic solutions (e.g., $\mathrm{Na_2O} + \mathrm{H_2O} \rightarrow 2\mathrm{NaOH}$). Hence, Statement (I) - that an element in the extreme left forms acidic oxides - is false. Analyzing Statement (II) The extreme right of the periodic table corresponds to the nonmetals in Groups 15, 16, 17 (and noble gases in Group 18). Nonmetal oxides (such as those of sulfur, phosphorus, chlorine) are generally acidic. When these oxides dissolve in water, they typically form acids. Example: $\mathrm{SO_3} + \mathrm{H_2O} \rightarrow \mathrm{H_2SO_4}$ (sulfuric acid) Example: $\mathrm{P_2O_5} + 3\mathrm{H_2O} \rightarrow 2\mathrm{H_3PO_4}$ (phosphoric acid) Example: $\mathrm{Cl_2O_7} + \mathrm{H_2O} \rightarrow 2\mathrm{HClO_4}$ (perchloric acid) Thus, Statement (II) - that acid is formed when water reacts with an oxide of a reactive element in the extreme right - is true. Conclusion Statement (I) is false. Statement (II) is true.

Question 65

Chemistry · Structure of Atom · Single correct

Given below are two statements: Statement (I): A spectral line will be observed for a $2p_x \rightarrow 2p_y$ transition. Statement (II): $2p_x$ and $2p_y$ are degenerate orbitals. In the light of the above statements, choose the correct answer from the options given below:

  1. Both Statement I and Statement II are true
  2. Statement I is false but Statement II is true
  3. Both Statement I and Statement II are false
  4. Statement I is true but Statement II is false

Answer: (a)

Solution

2p_x and 2p_y are degenerated orbitals hence having equal energy and therefore no spectral line will be observed for 2p_x $\rightarrow$ 2p_y transition.

Question 66

Chemistry · Organic Chemistry — Some Basic Principles & Techniques · Single correct

Given below are two statements: Statement (I): Nitrogen, sulphur, halogen and phosphorus present in an organic compound are detected by Lassaigne's Test. Statement (II): The elements present in the compound are converted from covalent form into ionic form by fusing the compound with Magnesium in Lassaigne's test. In the light of the above statements, choose the correct answer from the options given below:

  1. Statement I is false but Statement II is true
  2. Both Statement I and Statement II are true
  3. Both Statement I and Statement II are false
  4. Statement I is true but Statement II is false

Answer: (d)

Solution

The elements present in the compound are converted from covalent form into ionic form by fusing the compound with sodium in Lassaigne's test.

Question 67

Chemistry · Co-ordination Compounds · Single correct

Identify the homoleptic complex(es) that is/are low spin. (A) $[\mathrm{Fe(CN)_5NO}]^{2-}$ (B) $[\mathrm{CoF_6}]^{3-}$ (C) $[\mathrm{Fe(CN)_6}]^{4-}$ (D) $[\mathrm{Co(NH_3)_6}]^{3+}$ (E) $[\mathrm{Cr(H_2O)_6}]^{2+}$ Choose the correct answer from the options given below :

  1. only
  2. and (D) only
  3. and (C) only
  4. and (E) only

Answer: (b)

Solution

(A) $[\mathrm{Fe(CN)_5NO}]^{-2} \rightarrow$ Heteroleptic, $\mathrm{Fe^{+2}}$, $3\, d^6$, $t_{2g}^6 e_g^0$, $d^2 sp^3$, Low spin (3 d series + SFL) (B) $[\mathrm{CoF_6}]^{-3} \rightarrow$ Homoleptic, $sp^3 d^2$, High spin, $\mathrm{Co^{+3}}$, $3\, d^6$ (3 d series + WFL) (C) $[\mathrm{Fe(CN)_6}]^{-4} \rightarrow$ Homoleptic $\mathrm{Fe^{+2}}$, $3\, d^6$, $d^2 sp^3$, $t_{2g}^6 e_g^0$ Low spin (3 d series + SFL) (D) $[\mathrm{Co(NH_3)_6}]^{+3} \rightarrow$ Homoleptic, $\mathrm{Co^{+3}} 3\, d^6$, $d^2 sp^3$, $t_{2g}^6 e_g^0$, Low spin (3d series + SFL) (E) $[\mathrm{Cr(H_2O)_6}]^{+2} \rightarrow$ Homoleptic $\mathrm{Cr^{+2} 3\, d^4}$, $d^2 sp^3$, High spin $t_{2g}^3 e_g^1$ (3d series + WFL)

Question 68

Chemistry · Aldehydes, Ketones and Carboxylic Acids · Single correct

$\text{Residue (A)} + \mathrm{HCl(dil)} \rightarrow \text{Compound (B)}$ Structure of residue (A) and compound (B) formed respectively is:

Answer: (d)

Solution

The reaction starts with the oxidation of toluene to benzaldehyde using $\mathrm{CrO_2Cl_2}$ in $\mathrm{CS_2}$ and $\mathrm{H_3O^+}$. The benzaldehyde is then reacted with $\mathrm{NaHSO_3}$ to form a bisulfite adduct. This adduct, labeled as (A), is treated with dilute $\mathrm{HCl}$ to regenerate benzaldehyde, labeled as (B).

Question 69

Chemistry · Electrochemistry · Single correct

Given below are two statements : Statement (I) : Corrosion is an electrochemical phenomenon in which pure metal acts as an anode and impure metal as a cathode. Statement (II) : The rate of corrosion is more in alkaline medium than in acidic medium. In the light of the above statements, choose the correct answer from the options given below :

  1. Both Statement I and Statement II are true
  2. Statement I is false but Statement II is true
  3. Statement I is true but Statement II is false
  4. Both Statement I and Statement II are false

Answer: (c)

Solution

Statement I: Corrosion is an example of electrochemical phenomenon in which pure metal acts as anode and impure metal (rusted metal) acts as cathode. Statement II: Corrosion is more favourable in acid medium than alkaline so rate of corrosion is high in acid medium than alkaline.

Question 70

Chemistry · Hydrocarbons · Single correct

The alkane from below having two secondary hydrogens is:

  1. 4 - Ethyl-3,4-dimethyloctane
  2. 2,2,4,4-Tetramethylhexane
  3. 2, 2, 3, 3-Tetramethylpentane
  4. 2, 2, 4, 5-Tetramethylheptane

Answer: (b)

Solution

Question 71

Chemistry · Haloalkanes and Haloarenes · Numerical

The compound with molecular formula $C_6H_6$, which gives only one monobromo derivative and takes up four moles of hydrogen per mole for complete hydrogenation has _______ $\pi$ electrons.

Answer: 8

Solution

Since 4 moles of $\mathrm{H_2}$ is being added for complete hydrogenation, the degree of unsaturation $= 4$. No. of $\pi$ electrons in $\mathrm{C_6H_6} = 4 \times 2 = 8$.

Question 72

Chemistry · The d-and f-Block Elements · Numerical

Niobium (Nb) and ruthenium (Ru) have "$x$" and "$y$" number of electrons in their respective 4 d orbitals. The value of $x + y$ is ______.

Answer: 11

Solution

For Z = 41, Nb (Niobium) has the electron configuration $[\mathrm{Kr}] 4d^4 5s^1$. The number of electrons in 4d is 4, so $x = 4$. For Z = 44, Ru (Ruthenium) has the electron configuration $[\mathrm{Kr}] 4d^7 5s^1$. The number of electrons in 4d is 7, so $y = 7$. Given $x + y = 11$.

Question 73

Chemistry · Co-ordination Compounds · Numerical

The complex of $\mathrm{Ni}^{2+}$ ion and dimethyl glyoxime contains number of Hydrogen (H) atoms.

Answer: 14

Solution

Ni^{2+} with (dmg) forms [$\mathrm{Ni(dmg)_2}$]^{2+} having 2 H-Bonds as shown. The number of H atoms is 14.

Question 74

Chemistry · Thermodynamics · Numerical

Consider the following cases of standard enthalpy of reaction ($\Delta H_r^\circ$ in $\mathrm{kJmol^{-1}}$) $$\mathrm{C_2H_6(g) + \frac{7}{2}O_2(g) \rightarrow 2CO_2(g) + 3H_2O(l); \; \Delta H_1^\circ = -1550}$$ $$\mathrm{C(graphite) + O_2(g) \rightarrow CO_2(g); \; \Delta H_2^\circ = -393.5}$$ $$\mathrm{H_2(g) + \frac{1}{2}O_2(g) \rightarrow H_2O(l); \; \Delta H_3^\circ = -286}$$ The magnitude of $\Delta H_f^\circ\mathrm{_{C_2H_6(g)}}$ is ______ $\mathrm{kJmol^{-1}}$ (Nearest integer).

Answer: 4

Solution

Given the reaction $2\mathrm{C_{(graphite)}} + 3\mathrm{H_2(g)} \rightarrow \mathrm{C_2H_6(g)}$, we need to find $\Delta H_f$. For the reaction $\mathrm{C_2H_6(g)} + \frac{7}{2}\mathrm{O_2(g)} \rightarrow 2\mathrm{CO_2(g)} + 3\mathrm{H_2O(l)}$, $\Delta H_1 = -1550$. For the reaction $\mathrm{C_{(graphite)}} + \mathrm{O_2(g)} \rightarrow \mathrm{CO_2(g)}$, $\Delta H_2 = -393.5$. For the reaction $\mathrm{H_2(g)} + \frac{1}{2}\mathrm{O_2(g)} \rightarrow \mathrm{H_2O(l)}$, $\Delta H_3 = -286$. The formation enthalpy $\Delta H_f = 2\Delta H_2 + 3\Delta H_3 - \Delta H_1 = 95 \, \mathrm{kJ/mole^2}$.

Question 75

Chemistry · Solutions · Numerical

$20\,\mathrm{mL}$ of $2\,\mathrm{M\ NaOH}$ solution is added to $400\,\mathrm{mL}$ of $0.5\,\mathrm{M\ NaOH}$ solution. The final concentration of the solution is $\underline{\phantom{00}}\times10^{-2}\,\mathrm{M}$. (Nearest integer)

Answer: 57

Solution

Given $$M_F = \frac{M_1 V_1 + M_2 V_2}{V_1 + V_2}$$ Substitute the values: $$= \frac{2 \times 20 + 0.5 \times 400}{420} = 0.571M$$ $$= 57.1 \times 10^{-2} M$$ $$= 57$$