JEE Main 9 April 2024 Shift 2 question paper with solutions

JEE Main 9 April 2024 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 · Limits and Derivatives · Single correct

$\lim_{x\to0}\frac{e^{-(1+2x)^{\frac{1}{2x}}}}{x}$ is equal to

  1. 0
  2. $\frac{-2}{e}$
  3. e
  4. e - e^2

Answer: (c)

Solution

Given the limit expression: $$\lim_{x \to 0} \frac{e - e^{\frac{1}{2x} \ln(1+2x)}}{x}$$ We can rewrite it as: $$= \lim_{x \to 0} \frac{e \left( e^{\frac{\ln(1+2x)}{2x} - 1} - 1 \right)}{x}$$ Simplifying further: $$= \lim_{x \to 0} (-e) \frac{\ln(1+2x) - 2x}{2x^2}$$ Evaluating the limit: $$= (-e) \times (-1) \frac{4}{2 \times 2} = e$$

Question 2

Maths · Three Dimensional Geometry · Single correct

Consider the line $L$ passing through the points $(1, 2, 3)$ and $(2, 3, 5)$. The distance of the point $\left( \frac{11}{3}, \frac{11}{3}, \frac{19}{3} \right)$ from the line $L$ along the line $\frac{3x - 11}{2} = \frac{3y - 11}{1} = \frac{3z - 19}{2}$ is equal to

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

Answer: (d)

Solution

Given $\($ $\frac{x-1}{2-1}$ = $\frac{y-2}{3-2}$ = $\frac{z-3}{5-3}$ $\)$. This implies $\($ $\frac{x-1}{1}$ = $\frac{y-2}{1}$ = $\frac{z-3}{2}$ = $\lambda$ $\)$. Point B is $\($ (1+$\lambda$, 2+$\lambda$, 3+2$\lambda$) $\)$. The direction ratios of AB are $\($ $\left$ $\)$. For point B $\($ $\left$( $\frac{5}{3}$, $\frac{8}{3}$, $\frac{13}{3}$ $\right$) $\)$, we have $\($ $\frac{3\lambda - 8}{3\lambda - 5}$ = $\frac{2}{1}$ $\)$. This implies $\($ 3$\lambda$ - 8 = 6$\lambda$ - 10 $\)$. Solving gives $\($ 3$\lambda$ = 2 $\)$, so $\($ $\lambda$ = $\frac{2}{3}$ $\)$. The distance AB is $\($ $\frac{\sqrt{36 + 9 + 36}}{3}$ = $\frac{9}{3}$ = 3 $\)$.

Question 3

Maths · Differential Equations · Single correct

Let $\displaystyle\int_0^x \sqrt{1-(y'(t))^2}\,dt = \int_0^x y(t)\,dt, \quad 0 \le x \le 3, \quad y \ge 0, \quad y(0) = 0.$ Then at $x = 2$, $y'' + y + 1$ is equal to

  1. 1
  2. 2
  3. $\sqrt{2}$
  4. 1/2

Answer: (a)

Solution

Given $\sqrt{1 - \left(y'(x)\right)^2} = y(x)$. $$1 - \left(\frac{dy}{dx}\right)^2 = y^2$$ $$\left(\frac{dy}{dx}\right)^2 = 1 - y^2$$ $$\frac{dy}{\sqrt{1-y^2}} = dx OR \frac{dy}{\sqrt{1-y^2}} = -dx$$ This implies $\sin^{-1} y = x + c$, $\sin^{-1} y = -x + c$. For $x = 0$, $y = 0$ implies $c = 0$. Thus, $\sin^{-1} y = x$, as $y \geq 0$. Therefore, $\sin x = y$. This implies $\frac{dy}{dx} = \cos x$. Then, $\frac{d^2 y}{dx^2} = -\sin x$. Thus, $-\sin x + \sin x + 1 = 1$.

Question 4

Maths · Complex Numbers and Quadratic Equations · Single correct

Let $z$ be a complex number such that the real part of $\frac{z-2i}{z+2i}$ is zero. Then, the maximum value of $|z - (6 + 8i)|$ is equal to

  1. 12
  2. 10
  3. 8
  4. $\infty$

Answer: (a)

Solution

Given $\($ $\frac{z - 2i}{z + 2i}$ + $\frac{\overline{z} + 2i}{\overline{z} - 2i}$ = 0 $\)$. $\($ zz - 2iz - 2iz + 4(-1) + z$\overline{z}$ + 2zi + 2z$\overline{i}$ + 4(-1) = 0 $\)$ $\($ $\Rightarrow$ 2|z|^2 = 8 $\Rightarrow$ |z| = 2 $\)$ $\($ |z - (6 + 8i)|_{maximum} = 10 + 2 = 12 $\)$

Question 5

Maths · Applications of Integrals · Single correct

The area (in square units) of the region enclosed by the ellipse $x^2 + 3y^2 = 18$ in the first quadrant below the line $y = x$ is

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

Answer: (c)

Solution

Given the equation of the ellipse $\frac{x^2}{18} + \frac{y^2}{6} = 1$. The line $y = x$ intersects the ellipse. Solving $\frac{x^2}{18} + \frac{3x^2}{18} = 1$ gives $4x^2 = 18$ which implies $x^2 = \frac{9}{2}$. The integral to find the area is $\int_{\frac{3}{\sqrt{2}}}^{\frac{3\sqrt{2}}{2}} \frac{\sqrt{18 - x^2}}{\sqrt{3}} \, dx$. This evaluates to: $$\frac{1}{\sqrt{3}} \left( x \frac{\sqrt{18 - x^2}}{2} + \frac{18}{2} \sin^{-1} \frac{x}{3\sqrt{2}} \right)_{\frac{3}{\sqrt{2}}}^{\frac{3\sqrt{2}}{2}}$$ Simplifying gives: $$= \frac{1}{\sqrt{3}} \left( 9 \times \frac{\pi}{2} - \frac{3}{2\sqrt{2}} \times \frac{3\sqrt{3}}{\sqrt{2}} - 9 \times \frac{\pi}{6} \right)$$ The required area is: $$= \frac{1}{2} \times \frac{9}{2} + \left( \frac{18\pi}{6} - \frac{9\sqrt{3}}{4} \right) \frac{1}{\sqrt{3}}$$ This simplifies to $= \sqrt{3} \pi$.

Question 6

Maths · Conic Sections · Single correct

Let the foci of a hyperbola $H$ coincide with the foci of the ellipse $E$: $\frac{(x-1)^2}{100} + \frac{(y-1)^2}{75} = 1$ and the eccentricity of the hyperbola $H$ be the reciprocal of the eccentricity of the ellipse $E$. If the length of the transverse axis of $H$ is $\alpha$ and the length of its conjugate axis is $\beta$, then $3\alpha^2 + 2\beta^2$ is equal to

  1. 237
  2. 242
  3. 205
  4. 225

Answer: (d)

Solution

Given $e_1 = \sqrt{1 - \frac{75}{100}} = \frac{5}{10} = \frac{1}{2}$. $e_2 = 2$. $F_1(6, 1), F_2(-4, 1)$. $2ae_2 = 10 \Rightarrow a = \frac{5}{2} \Rightarrow 2a = 5$. $\Rightarrow \alpha = 5$. $4 = 1 + \frac{b^2}{a^2} \Rightarrow b^2 = 3a^2$. $b = \sqrt{3} \times \frac{5}{2}$. $\beta = 5\sqrt{3}$. $3\alpha^2 + 2\beta^2 = 3 \times 25 + 2 \times 25 \times 3 = 225$.

Question 7

Maths · Properties of Triangles · Single correct

Two vertices of a triangle ABC are $A(3, -1)$ and $B(-2, 3)$, and its orthocentre is $P(1, 1)$. If the coordinates of the point $C$ are $(\alpha, \beta)$ and the centre of the circle circumscribing the triangle $PAB$ is $(h, k)$, then the value of $(\alpha + \beta) + 2(h + k)$ equals

  1. 5
  2. 81
  3. 15
  4. 51

Answer: (a)

Solution

Given $M_{AB} = \frac{4}{5} \Rightarrow M_{DP} = \frac{5}{4}$. Equation of $PC$ is $y - 1 = \frac{5}{4}(x - 1)$ (1). $M_{AP} = \frac{2}{-2} = -1 \Rightarrow M_{BC} = +1$. Equation of $BC$ is $y - 3 = (x + 2)$ (2). On solving (1) and (2): $$x + 4 = \frac{5}{4}(x - 1) \Rightarrow 4x + 16 = 5x - 5 \Rightarrow \alpha = 21$$ $$\Rightarrow \beta = y = x + 5 = 26$$ $$\alpha + \beta = 47$$ Equation of $\perp$ bisector of $AP$: $$y - 0 = (x - 2) \ldots (3)$$ Equation of $\perp$ bisector of $AB$: $$y - 1 = \frac{5}{4}\left(x - \frac{1}{2}\right) \ldots (4)$$ On solving (3) $\&$ (4): $$(x - 3)4 = 5x - \frac{5}{2}$$ $$x = \frac{-19}{2} = h$$ $$y = \frac{-23}{2} = k$$ $$\Rightarrow 2\left(h + k\right) = -42$$

Question 8

Maths · Statistics · Single correct

If the variance of the frequency distribution \begin{tabular}{|c|c|c|c|c|c|c|} \hline $x$ & $c$ & $2c$ & $3c$ & $4c$ & $5c$ & $6c$\\ \hline $f$ & $2$ & $1$ & $1$ & $1$ & $1$ & $1$\\ \hline \end{tabular} is $160$, then the value of $c\in\mathbb{N}$ is:

  1. 7
  2. 8
  3. 5
  4. 6

Answer: (a)

Solution

\begin{tabular}{|c|c|c|c|c|c|c|} \hline $x$ & $C$ & $2C$ & $3C$ & $4C$ & $5C$ & $6C$ \\ \hline $f$ & $2$ & $1$ & $1$ & $1$ & $1$ & $1$ \\ \hline \end{tabular} $$\bar{x} = \frac{(2+2+3+4+5+6)C}{7} = \frac{22C}{7}$$ $$\text{Var}(x) = \frac{c^2\left(2 + 2^2 + 3^2 + 4^2 + 5^2 + 6^2\right)}{7} - \left(\frac{22c}{7}\right)^2$$ $$= \frac{92c^2}{7} - c^2 \times \frac{484}{49}$$ $$= \frac{(644 - 484)c^2}{49} = \frac{160c^2}{49}$$ $$160 = \frac{160 \times c^2}{49} \Rightarrow c = 7$$

Question 9

Maths · Relations and Functions · Single correct

Let the range of the function $f(x) = \frac{1}{2 + \sin 3x + \cos 3x}$, $x \in \mathbb{R}$ be $[a, b]$. If $\alpha$ and $\beta$ are respectively the A.M. and the G.M. of $a$ and $b$, then $\frac{\alpha}{\beta}$ is equal to

  1. $\pi$
  2. $\sqrt{\pi}$
  3. 2
  4. $\sqrt{2}$

Answer: (d)

Solution

Given $f(x) = \frac{1}{2 + \sin 3x + \cos 3x}$. Consider the expressions: $$\left[ \frac{1}{2 + \sqrt{2}}, \frac{1}{2 - \sqrt{2}} \right]$$ Let $\frac{\alpha}{\beta} = \frac{a + b}{2\sqrt{ab}} = \frac{1}{2} \left( \sqrt{\frac{a}{b}} + \sqrt{\frac{b}{a}} \right)$. Then, $$= \frac{1}{2} \left( \sqrt{\frac{2 - \sqrt{2}}{2 + \sqrt{2}}} + \sqrt{\frac{2 + \sqrt{2}}{2 - \sqrt{2}}} \right)$$ $$= \frac{(2 - \sqrt{2}) + (2 + \sqrt{2})}{2 \times \sqrt{2}} = \sqrt{2}$$

Question 10

Maths · Vector Algebra · Single correct

Between the following two statements: Statement I: Let $\vec{a} = \hat{i} + 2\hat{j} - 3\hat{k}$ and $\vec{b} = 2\hat{i} + \hat{j} - \hat{k}$. Then the vector $\vec{r}$ satisfying $\vec{a} \times \vec{r} = \vec{a} \times \vec{b}$ and $\vec{a} \cdot \vec{r} = 0$ is of magnitude $\sqrt{10}$. Statement II: In a triangle $ABC$, $\cos 2A + \cos 2B + \cos 2C \geq -\frac{3}{2}$.

  1. Statement I is incorrect but Statement II is correct.
  2. Both Statement I and Statement II are correct.
  3. Statement I is correct but Statement II is incorrect.
  4. Both Statement I and Statement II are incorrect.

Answer: (a)

Solution

Given $\bar{a} = \hat{i} + 2\hat{j} - 3\hat{k}$ and $\bar{a} = 2\hat{i} + \hat{j} - \hat{k}$. The cross product $\bar{a} \times \bar{r} = \bar{a} \times \bar{b}$ and $\bar{a} \cdot \bar{r} = 0$. This implies $\bar{a} \times (\bar{r} - \bar{b}) = 0$. Therefore, $\bar{a} = \lambda (\bar{r} - \bar{b})$. We have $\bar{a} \cdot \bar{a} = \lambda (\bar{a} \cdot \bar{r} - \bar{a} \cdot \bar{b})$. Solving $14 = -7\lambda$ gives $\lambda = -2$. Thus, $-\frac{\bar{a}}{2} = \bar{r} - \bar{b}$ implies $\bar{r} = \bar{b} - \frac{\bar{a}}{2}$. This results in $\bar{r} = \frac{2\bar{b} - \bar{a}}{2} = \frac{3\hat{i} + \hat{k}}{2}$. Statement (I) is incorrect. For the second part, $\cos 2A + \cos 2B + \cos 2C \geq -\frac{3}{2}$. Given $2A + 2B + 2C = 2\pi$, we have $\cos 2A + \cos 2B + \cos 2C = -1 - 4 \cos A \cdot \cos B \cdot \cos C$. This is greater than or equal to $-1 - 4 \times \frac{1}{2} \times \frac{1}{2} \times \frac{1}{2} = -\frac{3}{2}$. Statement (II) is correct.

Question 11

Maths · Limits and Derivatives · Single correct

\[ \lim_{x\to \frac{\pi}{2}} \left( \frac{ \displaystyle \int_{x^3}^{\left(\frac{\pi}{2}\right)^3} \left[ \sin\!\left(2t^{1/3}\right) +\cos\!\left(t^{1/3}\right) \right]\,dt }{ \left(x-\frac{\pi}{2}\right)^2 } \right) \]is equal to

  1. $\frac{5\pi^2}{9}$
  2. $\frac{9\pi^2}{8}$
  3. $\frac{11\pi^2}{10}$
  4. $\frac{3\pi^2}{2}$

Answer: (b)

Solution

The limit is given by $$ \lim_{x \to \frac{\pi}{2}} \frac{0 - \{ \sin(2x) + \cos(x) \} \cdot 3x^2}{2 \left( x - \frac{\pi}{2} \right)} $$ Simplifying, we have $$ = \lim_{x \to \frac{\pi}{2}} \frac{-\{ 2 \sin x \cos x + \cos x \} 3x^2}{2 \left( x - \frac{\pi}{2} \right)} $$ Using trigonometric identities, this becomes $$ = \lim_{x \to \frac{\pi}{2}} \left\{ \frac{2 \sin x \sin \left( \frac{\pi}{2} - x \right)}{2 \left( x - \frac{\pi}{2} \right)} + \frac{\sin \left( \frac{\pi}{2} - x \right)}{2 \left( \frac{\pi}{2} - x \right)} \right\} 3x^2 $$ Evaluating the limit, we get $$ = \left( 1(1) + \frac{1}{2} \right) 3 \left( \frac{\pi}{2} \right)^2 $$ Finally, the result is $$ = \frac{9\pi^2}{8} $$

Question 12

Maths · Binomial Theorem · Single correct

The sum of the coefficient of $x^{2/3}$ and $x^{-2/5}$ in the binomial expansion of $$\left(x^{2/3} + \frac{1}{2}x^{-2/5}\right)^9$$ is

  1. 21/4
  2. 63/16
  3. 19/4
  4. 69/16

Answer: (a)

Solution

$$T_{r+1} = {}^9C_r \left(x^{2/3}\right)^{9-r} \left(\frac{x^{-2/5}}{2}\right)^r$$ $$= {}^9C_r \left(\frac{1}{2}\right)^r x^{\left(6 - \frac{2r}{3} - \frac{2r}{5}\right)}$$ For coefficient of $x^{2/3}$, put $6 - \dfrac{2r}{3} - \dfrac{2r}{5} = \dfrac{2}{3}$ $\Rightarrow r = 5$ $\therefore$ Coefficient of $x^{2/3}$ is ${}^9C_5\left(\dfrac{1}{2}\right)^5$ For coefficient of $x^{-2/5}$, put $6 - \dfrac{2r}{3} - \dfrac{2r}{5} = -\dfrac{2}{5}$ $\Rightarrow r = 6$ $\therefore$ Coefficient of $x^{-2/5}$ is ${}^9C_6\left(\dfrac{1}{2}\right)^6$ $$\text{Sum} = {}^9C_5\left(\frac{1}{2}\right)^5 + {}^9C_6\left(\frac{1}{2}\right)^6 = \frac{21}{4}$$

Question 13

Maths · Matrices · Single correct

Let $\mathbf{B} = \begin{bmatrix} 1 & 3 \\ 1 & 5 \end{bmatrix}$ and $A$ be a $2 \times 2$ matrix such that $AB^{-1} = A^{-1}$. If $BCB^{-1} = A$ and $C^4 + \alpha C^2 + \beta I = O$, then $2\beta - \alpha$ is equal to

  1. 16
  2. 2
  3. 8
  4. 10

Answer: (d)

Solution

Given $\mathrm{BCB}^{-1} = A$. Therefore, $\left( \mathrm{BCB}^{-1} \right) \left( \mathrm{BCB}^{-1} \right) = A \cdot A$. This implies $\mathrm{BCIBC}^{-1} = A^2$. Thus, $\mathrm{BC}^2 \mathrm{B}^{-1} = A^2$. Therefore, $\mathrm{B}^{-1} \left( \mathrm{BC}^2 \mathrm{B}^{-1} \right) \mathrm{B} = \mathrm{B}^{-1} (A \cdot A) \mathrm{B}$. From equation (1), $$C^2 = A^{-1} \cdot A \cdot B$$ $$C^2 = B$$ Also, $\mathrm{AB}^{-1} = A^{-1}$. Thus, $\mathrm{AB}^{-1} \cdot A = A^{-1} A = I$. Therefore, $A^{-1} \left( \mathrm{AB}^{-1} A \right) = A^{-1} I$. Thus, $\mathrm{B}^{-1} A = A^{-1}$. Now, the characteristic equation of $C^2$ is $$|C_2 - \lambda I| = 0$$ $$|B - \lambda I| = 0$$ $$\begin{vmatrix} 1 - \lambda & 3 \\ 1 & 5 - \lambda \end{vmatrix} = 0$$ This implies $(1 - \lambda)(5 - 1) - 3 = 0 \Rightarrow (\lambda^2 - 6\lambda + 5) - 3 = 0$. Thus, $\lambda^2 - 6\lambda + 2 = 0$. Therefore, $\beta^2 - 6\beta + 2I = 0$. Thus, $C^4 - 6C^2 + 2I = 0$. Let $\alpha = -6$ and $\beta = 2$. Therefore, $2\beta - \alpha = 4 + 6 = 10$.

Question 14

Maths · Continuity and Differentiability · Single correct

If $\log_e y = 3 \sin^{-1} x$, then $(1-x^2) y'' - xy'$ at $x = \frac{1}{2}$ is equal to

  1. $3e^{\pi/6}$
  2. $9e^{\pi/2}$
  3. $3e^{\pi/2}$
  4. $9e^{\pi/6}$

Answer: (b)

Solution

Given $\ln(y) = 3 \sin^{-1} x$. $$\frac{1}{y} \cdot y' = 3 \left( \frac{1}{\sqrt{1-x^2}} \right)$$ $$\Rightarrow y' = \frac{3y}{\sqrt{1-x^2}} at x = \frac{1}{2}$$ $$\Rightarrow y' = 3e^{\frac{\pi}{6}} = 2 \sqrt{3} e^{\frac{\pi}{2}}$$ $$\Rightarrow y'' = 3 \left( \frac{\sqrt{1-x^2} y' - y \frac{1}{2\sqrt{1-x^2}} (-2x)}{(1-x^2)} \right)$$ $$\Rightarrow (1-x^2) y'' = 3 \left( 3y + \frac{xy}{\sqrt{1-x^2}} \right)$$ At $x = \frac{1}{2}$, $y = e^{3 \sin^{-1} \left( \frac{1}{2} \right)} = e^{3 \left( \frac{\pi}{6} \right)} = e^{\frac{\pi}{2}}$ $$\Rightarrow (1-x^2) y'' \big|_{at x = \frac{1}{2}} = 3 \left( 3e^{\frac{\pi}{2}} + \frac{1}{2} \left( e^{\frac{\pi}{2}} \right) \frac{\sqrt{3}}{2} \right)$$ $$= 3e^{\frac{\pi}{2}} \left( 3 + \frac{1}{\sqrt{3}} \right)$$ $$(1-x^2) y'' - xy' \big|_{at x = \frac{1}{2}}$$ $$= 3e^{\frac{\pi}{2}} \left( 3 + \frac{1}{\sqrt{3}} \right) - \frac{1}{2} \left( 2 \sqrt{3} e^{\frac{\pi}{2}} \right) = 9e^{\frac{\pi}{2}}$$

Question 15

Maths · Inverse Trigonometric Functions · Single correct

The integral $\int_{1/4}^{3/4} \cos \left( 2 \cot^{-1} \sqrt{\frac{1-x}{1+x}} \right) dx$ is equal to

  1. 1/2
  2. -1/2
  3. -1/4
  4. 1/4

Answer: (c)

Solution

Given $$I = \int_{1/4}^{3/4} \cos \left( 2 \cot^{-1} \left( \sqrt{\frac{1-x}{1+x}} \right) \right) dx$$ This can be rewritten as $$\int_{1/4}^{3/4} \cos \left( 2 \left( \tan^{-1} \sqrt{\frac{1+x}{1-x}} \right) \right) dx$$ Using the identity, we have $$\int_{1/4}^{3/4} \frac{1 - \tan^2 \left( \tan^{-1} \sqrt{\frac{1+x}{1-x}} \right)}{1 + \tan^2 \left( \tan^{-1} \sqrt{\frac{1+x}{1-x}} \right)} dx$$ This simplifies to $$\int_{1/4}^{3/4} \frac{1 - \left( \frac{1+x}{1-x} \right)}{1 + \left( \frac{1+x}{1-x} \right)} dx = \int_{1/4}^{3/4} \frac{-2x}{2} dx$$ Which further simplifies to $$\int_{1/4}^{3/4} (-x) dx = - \left( \frac{x^2}{2} \right) \bigg|_{1/4}^{3/4}$$ Evaluating the integral, we get $$= -\frac{1}{2} \left[ \frac{9}{16} - \frac{1}{16} \right]$$ Finally, $$= -\frac{1}{4}$$

Question 16

Maths · Sequences and Series · Single correct

Let a, ar, ar^2, be an infinite G.P. If $\sum_{n=0}^{\infty} ar^n = 57$ and $\sum_{n=0}^{\infty} a^3 r^{3n} = 9747$, then $a + 18r$ is equal to

  1. 46
  2. 38
  3. 31
  4. 27

Answer: (c)

Solution

Given $$\sum_{n=0}^{\infty} ar^n = 57$$ $$a + ar + ar^2 + \infty = 57$$ $$\frac{a}{1-r} = 57 \ldots (I)$$ $$\sum_{n=0}^{\infty} a^3 r^{3n} = 9747$$ $$a^3 + a^3 \cdot r^3 + a^3 \cdot r^6 + \ldots = 9746$$ $$\frac{a^3}{1-r^3} = 9746 \ldots (II)$$ From (I) and (II), $$\left(\frac{a}{1-r}\right)^3 = \frac{57^3}{9717} = 19$$ Thus, $$a = 19$$ Therefore, $$a + 18r = 19 + 18 \times \frac{2}{3} = 31$$ On solving, $$r = \frac{2}{3}$$ and $$r = \frac{3}{2}$$ (rejected) Thus, $$a = 19$$ Therefore, $$a + 18r = 19 + 18 \times \frac{2}{3} = 31$$

Question 17

Maths · Probability · Single correct

If an unbiased dice is rolled thrice, then the probability of getting a greater number in the $i^{th}$ roll than the number obtained in the $(i-1)^{th}$ roll, $i = 2, 3$, is equal to

  1. 3/54
  2. 2/54
  3. 1/54
  4. 5/54

Answer: (d)

Solution

Favourable cases = $^6C_3$ Total outcomes = $6^3$ Probability of getting greater number than previous $$one = \frac{^6C_3}{r^3} = \frac{20}{216} = \frac{5}{54}$$

Question 18

Maths · Integrals · Single correct

The value of the integral $\int_{-1}^{2} \log_e \left( x + \sqrt{x^2 + 1} \right) \, dx$ is

  1. $\sqrt{5} - \sqrt{2} + \log_e \left( \frac{7 + 4 \sqrt{5}}{1 + \sqrt{2}} \right)$
  2. $\sqrt{5} - \sqrt{2} + \log_e \left( \frac{9 + 4 \sqrt{5}}{1 + \sqrt{2}} \right)$
  3. $\sqrt{2} - \sqrt{5} + \log_e \left( \frac{7 + 4 \sqrt{5}}{1 + \sqrt{2}} \right)$
  4. $\sqrt{2} - \sqrt{5} + \log_e \left( \frac{9 + 4 \sqrt{5}}{1 + \sqrt{2}} \right)$

Answer: (d)

Solution

Given $$I = \int_{-1}^{2} \log_e \left( x + \sqrt{x^2 + 1} \right) dx$$ We have $$= x \log_e \left( x + \sqrt{x^2 + 1} \right) - \int_{-1}^{2} \left( \frac{1 + \frac{x}{\sqrt{x^2 + 1}}}{x + \sqrt{x^2 + 1}} \right) dx$$ This simplifies to $$= x \log_e \left( x + \sqrt{x^2 + 1} \right) - \int_{-1}^{2} \frac{x}{\sqrt{x^2 + 1}} dx$$ Further simplifying, we get $$= x \log_e \left( x + \sqrt{x^2 + 1} \right) - \sqrt{x^2 + 1} \bigg|_{-1}^{2}$$ Evaluating the limits, $$= (2 \log_e (2 + \sqrt{5}) - \sqrt{5})$$ $$- (- \log_e (-1 + \sqrt{2}) - \sqrt{2})$$ This results in $$= \log_e (2 + \sqrt{5})^2 - \sqrt{5} + \log_e (\sqrt{2} - 1) + \sqrt{2}$$ Simplifying further, $$= \log_e (2 + \sqrt{5})^2 - \sqrt{5} + \log_e (\sqrt{2} - 1) + \sqrt{2}$$ Finally, $$= \sqrt{2} - \sqrt{5} + \log_e \left( \frac{(2 + \sqrt{5})^2}{\sqrt{2} + 1} \right)$$ Which simplifies to $$= \sqrt{2} - \sqrt{5} + \log_e \left( \frac{9 + 4\sqrt{5}}{\sqrt{2} + 1} \right)$$

Question 19

Maths · Complex Numbers and Quadratic Equations · Single correct

Let $\alpha$, $\beta$; $\alpha$ > $\beta$, be the roots of the equation $x^2 - \sqrt{2}x - \sqrt{3} = 0$. Let $P_n = \alpha^n - \beta^n, n \in \mathbb{N}$. Then $$(11\sqrt{3} - 10\sqrt{2})P_{10} + (11\sqrt{2} + 10)P_{11} - 11P_{12}$$ is equal to

  1. 10$\sqrt{3}$P_9
  2. 11$\sqrt{3}$P_9
  3. 10$\sqrt{2}$P_9
  4. 11$\sqrt{2}$P_9

Answer: (a)

Solution

Given $x^2 - \sqrt{2}x - \sqrt{3} = 0 \langle \alpha, \beta \rangle$. $\alpha^{n+2} - \sqrt{2}\alpha^{n+1} - \sqrt{3}\alpha^n = 0$ and $\beta^{n+2} - \sqrt{2}\beta^{n+1} - \sqrt{3}\beta^n = 0$. Subtracting $$(\alpha^{n+2} - \beta^{n+2}) - \sqrt{2}(\alpha^{n+1} - \beta^{n+1}) - \sqrt{3}(\alpha^n - \beta^n) = 0$$ $$\Rightarrow P_{n+2} - \sqrt{2}P_{n+1} - \sqrt{3}P_n = 0$$ Put $n = 10$ $$P_{12} - \sqrt{2}P_{11} - \sqrt{3}P_{10} = 0$$ $n = 9$ $$P_{11} - \sqrt{2}P_{10} - \sqrt{3}P_9 = 0$$ $$11\left(\sqrt{3} \cdot P_{10} + \sqrt{2}P_{11} - P_{11}\right) - 10$$ $$= 0 - 10(-\sqrt{3}P_9) = 10\sqrt{3}P_9$$

Question 20

Maths · Vector Algebra · Single correct

Let $\vec{a} = 2\hat{i} + \alpha \hat{j} + \hat{k}$, $\vec{b} = -\hat{i} + \beta \hat{j} - \hat{k}$, $\vec{c} = \beta \hat{j} - \hat{k}$, where $\alpha$ and $\beta$ are integers and $\alpha \beta = -6$. Let the values of the ordered pair $(\alpha, \beta)$, for which the area of the parallelogram of diagonals $\vec{a} + \vec{b}$ and $\vec{b} + \vec{c}$ is $\frac{\sqrt{21}}{2}$, be $(\alpha_1, \beta_1)$ and $(\alpha_2, \beta_2)$. Then $\alpha_1^2 + \beta_1^2 - \alpha_2 \beta_2$ is equal to

  1. 19
  2. 17
  3. 24
  4. 21

Answer: (a)

Solution

Area of parallelogram $= \frac{1}{2} \left| \vec{d_1} \times \vec{d_2} \right|$. $$A = \frac{1}{2} \left| (\vec{a} + \vec{b}) \times (\vec{b} + \vec{c}) \right| = \frac{\sqrt{21}}{2}$$ So, $\vec{a} + \vec{b} = \hat{i} + \alpha \hat{j} + 2 \hat{k}$ and $\vec{b} + \vec{c} = -\hat{i} + \beta \hat{j}$. $$\begin{vmatrix} \vec{a} + \vec{b} \times \vec{b} + \vec{c} \end{vmatrix} = \begin{vmatrix} \hat{i} & \hat{j} & \hat{k} \\ 1 & \alpha & 2 \\ -1 & \beta & 0 \end{vmatrix}$$ $$= \hat{i}(-2\beta) - \hat{j}(2) + \hat{k}(\beta + \alpha)$$ $$\left| (\vec{a} + \vec{b}) \times (\vec{b} + \vec{c}) \right| = \sqrt{4\beta^2 + 4 + (\alpha + \beta)^2} = \sqrt{21}$$ $$4\beta^2 + 4 + \alpha^2 + \beta^2 + 2\alpha\beta = 21$$ $$\alpha^2 + 5\beta^2 - 12 = 17$$ $$\alpha^2 + 5\beta^2 = 29$$ and $\alpha\beta = -6$. Given $\alpha, \beta$ are integers, so, $\alpha = -3, \beta = 2$ or $\alpha = 3, \beta = -2$. $$(\alpha_1, \beta_1) = (-3, 2)$$ $$(\alpha_2, \beta_2) = (3, -2)$$ $$\alpha_1^2 + \beta_1^2 - \alpha_2\beta_2 = 9 + 4 + 6 = 19$$

Question 21

Maths · Conic Sections · Numerical

Consider the circle $\mathcal{C} : x^2 + y^2 = 4$ and the parabola $P : y^2 = 8x$. If the set of all values of $\alpha$, for which three chords of the circle $\mathcal{C}$ on three distinct lines passing through the point $(\alpha, 0)$ are bisected by the parabola $P$ is the interval $(p, q)$, then $(2q - p)^2$ is equal to

Answer: 80

Solution

Given $T = S_1$. $x_1 + y_1 = x_1^2 + y_1^2$. $\alpha x_1 = x_1^2 + y_1^2$. $\alpha (2t^2) = 4t^4 + 16t^2$. $\alpha = 2t^2 + 8$. $\frac{\alpha-8}{20}=t^2$ Also, $4t^4 + 16t^2 - 4 < 0$. $t^2 = -2 + \sqrt{5}$. $\alpha = 4 + 2\sqrt{5}$. Therefore, $\alpha \in (8, 4 + 2\sqrt{5})$. Thus, $(2q - p)^2 = 80$.

Question 22

Maths · Applications of Derivatives · Numerical

Let the set of all values of $p$, for which $f(x) = (p^2 - 6p + 8) \left( \sin^2 2x - \cos^2 2x \right) + 2(2 - p)x + 7$ does not have any critical point, be the interval $(a, b)$. Then $16ab$ is equal to

Answer: 252

Solution

Given $$f(x) = - (p^2 - 6p + 8) \cos 4n + 2(2 - p)n + 7$$ $$f^1(x) = +4 (p^2 - 6p + 8) \sin 4x + (4 - 2p) \neq 0$$ $$\sin 4x \neq \frac{2p - 4}{4(p - 4)(p - 2)}$$ $$\sin 4x \neq \frac{2(p - 2)}{4(p - 4)(p - 2)}$$ $$p \neq 2$$ $$\sin 4x \neq \frac{1}{2(p - 4)}$$ $$\Rightarrow \left| \frac{1}{2(p - 4)} \right| > 1$$ On solving we get $$\therefore p \in \left( \frac{7}{2}, \frac{9}{2} \right)$$ Hence $a = \frac{7}{2}$, $b = \frac{9}{2}$ $$\therefore 16ab = 252$$

Question 23

Maths · Differential Equations · Numerical

For a differentiable function $f : \mathbb{R} \to \mathbb{R}$, suppose $f'(x) = 3f(x) + \alpha$, where $\alpha \in \mathbb{R}$, $f(0) = 1$ and $\lim_{x \to -\infty} f(x) = 7$. Then $9f(-\log_e 3)$ is equal to

Answer: 61

Solution

\[ \frac{dy}{dx}-3y=\alpha \] If \[ \text{I.F.}=e^{\int -3\,dx}=e^{-3x} \] \[ y\,e^{-3x}=\int e^{-3x}\cdot \alpha\,dx \] \[ y\,e^{-3x}=\frac{\alpha e^{-3x}}{-3}+c \] \[ (*e^{3x}) \] \[ y=-\frac{\alpha}{3}+Ce^{3x} \] On substituting \(x=0,\ y=1\), \[ 1=-\frac{\alpha}{3}+C \] \[ C=1+\frac{\alpha}{3} \] We get \[ y=-\frac{\alpha}{3}+\left(1+\frac{\alpha}{3}\right)e^{3x} \] \[ y=7-6e^{3x} \] \[ 9f(-\log_e 3)=61 \]

Question 24

Maths · Permutations and Combinations · Numerical

The number of integers, between 100 and 1000 having the sum of their digits equals to 14, is

Answer: 70

Solution

Given $N = abc$. (i) All distinct digits $a + b + c = 14$ $a \geq 1$ $b, c \in \{0 to 9\}$ By hit and trial: 8 cases $(6, 5, 3)$ $(7, 6, 1)$ $(7, 5, 2)$ $(7, 4, 3)$ $(8, 6, 0)$ $(8, 5, 1)$ $(8, 4, 2)$ $(9, 4, 1)$ $(9, 3, 2)$ $(9, 5, 0)$ (ii) 2 same, 1 different $a = b; c$ $2a + c = 14$ By values: $$\begin{array}{c} (3, 8) \\ (4, 6) \\ (5, 4) \\ (6, 2) \\ (7, 0) \end{array} \frac{3!}{2!} \times 5 - 1$$ $= 14$ cases (iii) All same: $3a = 14$ $a = \frac{14}{3} \times rejected$ 0 cases Hence, Total cases: $8 \times 3! + 2 \times (4) + 14$ $= 48 + 22$ $= 70$

Question 25

Maths · Sets · Numerical

Let $A = \{(x, y) : 2x + 3y = 23, x, y \in \mathbb{N}\}$ and $B = \{x : (x, y) \in A\}$. Then the number of one-one functions from $A$ to $B$ is equal to

Answer: 24

Solution

Given the equation $2x + 3y = 23$. For $x = 1$, $y = 7$. For $x = 4$, $y = 5$. For $x = 7$, $y = 3$. For $x = 10$, $y = 1$. Set $A = \{(1, 7), (4, 5), (7, 3), (10, 1)\}$ and $B = \{1, 4, 7, 10\}$. The number of one-one functions from $A$ to $B$ is equal to $4!$.

Question 26

Maths · Conic Sections · Numerical

Let $A, B$ and $C$ be three points on the parabola $y^2 = 6x$ and let the line segment $AB$ meet the line $L$ through $C$ parallel to the $x$-axis at the point $D$. Let $M$ and $N$ respectively be the feet of the perpendiculars from $A$ and $B$ on $L$. Then $$\left( \frac{AM \cdot BN}{CD} \right)^2$$ is equal to .

Answer: 36

Solution

Given $m_{AB} = m_{AD}$, we have $$\frac{2}{t_1 + t_2} = \frac{2a (t_1 - t_3)}{at_1^2 - \alpha}$$ which implies $$at_1^2 - \alpha = a \{t_2^1 - t_1 t_3 + t_1 t_2 - t_2 t_3\}$$ leading to $$\alpha = a (t_1 t_3 + t_2 t_3 - t_1 t_2).$$ The length $AM = |2a (t_1 - t_3)|$, and $BN = |2a (t_2 - t_3)|$. For $CD = |at_3^2 - \alpha|$, we have $$CD = |at_3^2 - a (t_1 t_3 + t_2 t_3 - t_1 t_2)|$$ which simplifies to $$= a |t_3^2 - t_1 t_3 - t_2 t_3 + t_1 t_2|$$ and further to $$= a |t_3 (t_3 - t_1) - t_2 (t_3 - t_1)|$$ resulting in $$CD = a |(t_3 - t_2) (t_3 - t_1)|.$$ Therefore, $$\left(\frac{AM \cdot BN}{CD}\right)^2 = \left\{\frac{2a (t_1 - t_3) \cdot 2a (t_2 - t_3)}{a (t_3 - t_2) (t_3 - t_1)}\right\}^2.$$ Simplifying gives $$16a^2 = 16 \times \frac{9}{4} = 36.$$

Question 27

Maths · Three Dimensional Geometry · Numerical

The square of the distance of the image of the point $(6, 1, 5)$ in the line $\frac{x-1}{3} = \frac{y}{2} = \frac{z-2}{4}$, from the origin is

Answer: 62

Solution

Let M(3$\lambda$ + 1, 2$\lambda$, 4$\lambda$ + 2). $\overrightarrow{\mathrm{AM}}$ $\cdot$ $\overrightarrow{\mathbf{b}}$ = 0. $\Rightarrow$ 9$\lambda$ - 15 + 4$\lambda$ - 2 + 16$\lambda$ - 12 = 0. $\Rightarrow$ 29$\lambda$ = 29. $\Rightarrow$ $\lambda$ = 1. M(4, 2, 6), I = (2, 3, 7). Required Distance = $\sqrt{4 + 9 + 49}$ = $\sqrt{62}$. Ans. 62

Question 28

Maths · Sequences and Series · Numerical

If $(\frac{1}{\alpha+1} + \frac{1}{\alpha+2} + \cdots + \frac{1}{\alpha+1012})$ - $(\frac{1}{2 \cdot 1} + \frac{1}{4 \cdot 3} + \frac{1}{6 \cdot 5} + \cdots + \frac{1}{2024 \cdot 2023})$ = $\frac{1}{2024}$, then $\alpha$ is equal to ____

Answer: 1011

Solution

Given $\($ $\left$( $\frac{1}{\alpha + 1}$ + $\frac{1}{\alpha + 2}$ + $\cdots$ + $\frac{1}{\alpha + 2012}$ $\right$) - $\left$$\{$ $\left$( $\frac{1}{1}$ - $\frac{1}{2}$ $\right$) + $\left$( $\frac{1}{3}$ - $\frac{1}{4}$ $\right$) + $\cdots$ + $\left$( $\frac{1}{2023}$ - $\frac{1}{2024}$ $\right$) $\right$$\}$ = $\frac{1}{2024}$ $\)$ $\($ $\Rightarrow$ $\left$( $\frac{1}{\alpha + 1}$ + $\frac{1}{\alpha + 2}$ + $\cdots$ + $\frac{1}{\alpha + 2012}$ $\right$) - $\left$$\{$ $\left$( $\frac{1}{1}$ - $\frac{1}{2}$ $\right$) + $\left$( $\frac{1}{1}$ + $\frac{1}{2}$ + $\frac{1}{3}$ - $\frac{1}{4}$ $\right$) + $\cdots$ + $\frac{1}{2023}$ - $\frac{1}{2024}$ - 2 $\left$( $\frac{1}{2}$ + $\frac{1}{4}$ + $\cdots$ + $\frac{1}{2022}$ $\right$) $\right$$\}$ = $\frac{1}{2024}$ $\)$ $\($ $\Rightarrow$ $\left$( $\frac{1}{\alpha + 1}$ + $\frac{1}{\alpha + 2}$ + $\cdots$ + $\frac{1}{\alpha + 2012}$ $\right$) - $\left$( $\frac{1}{1}$ + $\frac{1}{2}$ + $\cdots$ + $\frac{1}{2023}$ $\right$) + $\frac{1}{2024}$ + $\left$( $\frac{1}{1}$ + $\frac{1}{2}$ + $\cdots$ + $\frac{1}{1011}$ $\right$) = $\frac{1}{2024}$ $\)$ $\($ $\Rightarrow$ $\frac{1}{\alpha + 1}$ + $\frac{1}{\alpha + 2}$ + $\cdots$ + $\frac{1}{\alpha + 2012}$ = $\frac{1}{1012}$ + $\frac{1}{1013}$ + $\cdots$ + $\frac{1}{2023}$ $\)$ $\($ $\Rightarrow$ $\alpha$ = 1011 $\)$

Question 29

Maths · Inverse Trigonometric Functions · Numerical

Let the inverse trigonometric functions take principal values. The number of real solutions of the equation $$2 \sin^{-1} x + 3 \cos^{-1} x = \frac{2\pi}{5}$$, is

Answer: 0

Solution

Given $2 \sin^{-1} x + 3 \cos^{-1} x = \frac{2\pi}{5}$. Therefore, $$\pi + \cos^{-1} x = \frac{2\pi}{5}$$ which implies $$\cos^{-1} x = \frac{-3\pi}{5}$$ which is not possible. Ans. 0

Question 30

Maths · Determinants · Numerical

Consider the matrices : $A = \begin{bmatrix} 2 & -5 \\ 3 & m \end{bmatrix}$, $B = \begin{bmatrix} 20 \\ m \end{bmatrix}$ and $X = \begin{bmatrix} x \\ y \end{bmatrix}$. Let the set of all $m$, for which the system of equations $AX = B$ has a negative solution (i.e., $x < 0$ and $y < 0$), be the interval $(a, b)$. Then $8 \int_a^b |A| \, dm$ is equal to ________

Answer: 450

Solution

Given matrices $A = \begin{pmatrix} 2 & -5 \\ 3 & m \end{pmatrix}$ and $B = \begin{pmatrix} 20 \\ m \end{pmatrix}$, and vector $X = \begin{pmatrix} x \\ y \end{pmatrix}$. The equations are: $$2x - 5y = 20 \ldots (1)$$ $$3x + my = m \ldots (2)$$ From equation (2), solving for $y$: $$y = \frac{2m - 60}{2m + 15}$$ For $y < 0$, we have $m \in \left( -\frac{15}{2}, 30 \right)$. Solving for $x$: $$x = \frac{25}{2m + 15}$$ For $x < 0$, we have $m \in \left( -\frac{15}{2}, 0 \right)$. Thus, $m \in \left( -\frac{15}{2}, 0 \right)$. The determinant $|A| = 2m + 15$. Now, evaluate the integral: $$8 \int_{-\frac{15}{2}}^{0} (2m + 15) \, dm = 8 \left\{ m^2 + 15m \right\}_{-\frac{15}{2}}^{0}$$ This simplifies to: $$\Rightarrow 8 \left\{ 0 - \left( \frac{225}{4} - \frac{225}{2} \right) \right\}$$ Finally, we have: $$= 8 \times \frac{225}{4} = 450$$

Physics

Question 31

Physics · Nuclei · Single correct

A nucleus at rest disintegrates into two smaller nuclei with their masses in the ratio of 2 : 1. After disintegration they will move :

  1. in the same direction with same speed.
  2. in opposite directions with the same speed.
  3. in opposite directions with speed in the ratio of 2 : 1 respectively.
  4. in opposite directions with speed in the ratio of 1 : 2 respectively.

Answer: (d)

Solution

By conservation of momentum $$p_i = p_f$$ $$0 = m_1 u_1 + m_2 u_2$$ $$\frac{u_1}{u_2} = -\left[ \frac{1}{2} \right] as \frac{m_1}{m_2} = \frac{2}{1}$$ move in opposite direction with speed ratio 1 : 2

Question 32

Physics · Ray Optics and Optical Instruments · Single correct

The following figure represents two biconvex lenses $L_1$ and $L_2$ having focal length 10 cm and 15 cm respectively. The distance between $L_1$ & $L_2$ is :

  1. 10 cm
  2. 35 cm
  3. 25 cm
  4. 15 cm

Answer: (c)

Solution

Given $D = f_1 + f_2 = 25 \, \mathrm{cm}$. Paraxial parallel rays pass through focus and ray from focus of convex lens will become parallel.

Question 33

Physics · Kinetic Theory · Single correct

The temperature of a gas is $-78^\circ \mathrm{C}$ and the average translational kinetic energy of its molecules is $K$. The temperature at which the average translational kinetic energy of the molecules of the same gas becomes $2K$ is:

  1. $127^\circ \mathrm{C}$
  2. $117^\circ \mathrm{C}$
  3. $-39^\circ \mathrm{C}$
  4. $-78^\circ \mathrm{C}$

Answer: (b)

Solution

K.E = $\frac{nf_1RT}{2}$ $T_i = -78^\circ \mathrm{C} \rightarrow 273 + [-78^\circ \mathrm{C}] = 195 \, \mathrm{K}$ K.E $\propto T$ To double the K.E energy temp also become double $T_f = 390 \, \mathrm{K}$ $T_f = 117^\circ \mathrm{C}$

Question 34

Physics · Atoms · Single correct

A hydrogen atom in ground state is given an energy of $10.2\,\mathrm{eV}$. How many spectral lines will be emitted due to transition of electrons?

  1. 6
  2. 3
  3. 10
  4. 1

Answer: (d)

Solution

Hydrogen will be in first excited state therefore it will emit one spectral line corresponding to transition between energy level 2 to 1.

Question 35

Physics · Electromagnetic Waves · Single correct

The magnetic field in a plane electromagnetic wave is $B_y = (3.5 \times 10^{-7}) \sin(1.5 \times 10^3 x + 0.5 \times 10^{11} t) \mathrm{T}$. The corresponding electric field will be:

  1. $E_y = 10.5 \sin(1.5 \times 10^3 x + 0.5 \times 10^{11} t) \mathrm{Vm}^{-1}$
  2. $E_z = 1.17 \sin(1.5 \times 10^3 x + 0.5 \times 10^{11} t) \mathrm{Vm}^{-1}$
  3. $E_y = 1.17 \sin(1.5 \times 10^3 x + 0.5 \times 10^{11} t) \mathrm{Vm}^{-1}$
  4. $E_z = 105 \sin(1.5 \times 10^3 x + 0.5 \times 10^{11} t) \mathrm{Vm}^{-1}$

Answer: (d)

Solution

Given $E_0 = B_0 C$. $$E_0 = 3 \times 10^8 \times (3.5 \times 10^{-7}) \sin(1.5 \times 10^3 x + 0.5 \times 10^{11} t)$$ $$E_0 = 105 \sin(1.5 \times 10^3 x + 0.5 \times 10^{11} t) \, \mathrm{Vm^{-1}}$$ Data inconsistent while calculating speed of wave. You can challenge for data.

Question 36

Physics · Electromagnetic Induction · Single correct

A square loop of side 15 cm being moved towards right at a constant speed of 2 $\mathrm{cm/s}$ as shown in figure. The front edge enters the 50 $\mathrm{cm}$ wide magnetic field at t = 0. The value of induced emf in the loop at t = 10 $\mathrm{s}$ will be:

  1. 0.3 $\mathrm{mV}$
  2. zero
  3. 4.5 $\mathrm{mV}$
  4. 3 $\mathrm{mV}$

Answer: (b)

Solution

At $t = 10 \, sec$ complete loop is in magnetic field therefore no change in flux. $$e = \frac{d\phi}{dt} = 0$$ $e = 0$ for complete loop.

Question 37

Physics · Motion in a Straight Line · Single correct

Two cars are travelling towards each other at speed of $20 \, \mathrm{m \, s^{-1}}$ each. When the cars are $300 \, \mathrm{m}$ apart, both the drivers apply brakes and the cars retard at the rate of $2 \, \mathrm{m \, s^{-2}}$. The distance between them when they come to rest is:

  1. $200 \, \mathrm{m}$
  2. $50 \, \mathrm{m}$
  3. $100 \, \mathrm{m}$
  4. $25 \, \mathrm{m}$

Answer: (c)

Solution

Question 38

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

The $I - V$ characteristics of an electronic device shown in the figure. The device is:

  1. a diode which can be used as a rectifier
  2. a zener diode which can be used as a voltage regulator
  3. a transistor which can be used as an amplifier
  4. a solar cell

Answer: (b)

Solution

Theory Zener diode used as voltage regulator

Question 39

Physics · Mechanical Properties of Fluids · Single correct

The excess pressure inside a soap bubble is thrice the excess pressure inside a second soap bubble. The ratio between the volume of the first and the second bubble is:

  1. 1 : 9
  2. 1 : 3
  3. 1 : 27
  4. 1 : 81

Answer: (c)

Solution

Given the equations: $$P_1 - P_0 = \frac{4T}{r_1}$$ $$P_2 - P_0 = \frac{4T}{r_2}$$ We have: $$P_1 - P_0 = 3(P_2 - P_0)$$ Substituting the expressions: $$\frac{4T}{r_1} = 3 \cdot \frac{4T}{r_2}$$ Solving for $r_2$: $$r_2 = 3r_1$$ Now, considering the volumes: $$\frac{V_1}{V_2} = \frac{\frac{4}{3} \pi r_1^3}{\frac{4}{3} \pi r_2^3} = \frac{1}{27}$$

Question 40

Physics · Physical World, Units and Measurements · Single correct

The de-Broglie wavelength associated with a particle of mass $m$ and energy $E$ is $h/\sqrt{2mE}$. The dimensional formula for Planck's constant is :

  1. $\mathrm{ML^2 T^{-1}}$
  2. $\mathrm{ML^{-1} T^{-2}}$
  3. $\mathrm{MLT^{-2}}$
  4. $\mathrm{M^2 L^2 T^{-2}}$

Answer: (a)

Solution

Given $\lambda = \frac{h}{\sqrt{2mE}}$ or $E = h\nu$. $$[ML^2 T^{-2}] = h [T^{-1}]$$ Therefore, $$h = [ML^2 T^{-1}]$$

Question 41

Physics · Gravitation · Single correct

A satellite of $10^3 \, \mathrm{kg}$ mass is revolving in circular orbit of radius $2R$. If $\frac{10^4 R}{6} \, \mathrm{J}$ energy is supplied to the satellite, it would revolve in a new circular orbit of radius (use $g = 10 \, \mathrm{m/s^2}$, $R = radius of earth$)

  1. $2.5R$
  2. $3R$
  3. $4R$
  4. $6R$

Answer: (c)

Solution

Total energy = $\frac{-GMm}{2(2R)}$. If energy = $\frac{10^4 R}{6}$ is added then $$\frac{-GMm}{4R} + \frac{10^4 R}{6} = \frac{-GMm}{2r}$$ where r is new radius of revolving and $g = \frac{GM}{R^2}$. $$\frac{-mgR}{4} + \frac{10^4 R}{6} = \frac{-mgR^2}{2r} (m = 10^3 \, \mathrm{kg})$$ $$-10^3 \times 10 \times R + \frac{10^4 R}{6} = \frac{-10^3 \times 10 \times R^2}{2r}$$ $$-\frac{1}{4} + \frac{1}{6} = \frac{-R}{2r}$$ $$r = 6R$$

Question 42

Physics · Current Electricity · Single correct

The effective resistance between $A$ and $B$, if resistance of each resistor is $R$, will be

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

Answer: (a)

Solution

From symmetry we can remove two middle resistance. New circuit is

Question 43

Physics · Electric Charges and Fields · Single correct

Five charges $+q$, $+5q$, $-2q$, $+3q$ and $-4q$ are situated as shown in the figure. The electric flux due to this configuration through the surface $S$ is:

  1. $\frac{4q}{\varepsilon_0}$
  2. $\frac{5q}{\varepsilon_0}$
  3. $\frac{q}{\varepsilon_0}$
  4. $\frac{3q}{\varepsilon_0}$

Answer: (a)

Solution

As per Gauss's theorem, $$\phi = \frac{q_{in}}{\varepsilon_0} = \frac{q + (-2q) + 5q}{\varepsilon_0}$$ $$\frac{4q}{\varepsilon_0}$$

Question 44

Physics · Moving Charges and Magnetism · Single correct

A proton and a deutron $\left( q = +e, m = 2.0u \right)$ having same kinetic energies enter a region of uniform magnetic field $\vec{B}$, moving perpendicular to $\vec{B}$. The ratio of the radius $r_d$ of deutron path to the radius $r_p$ of the proton path is:

  1. $\sqrt{2}$ : 1
  2. 1 : 1
  3. 1 : $\sqrt{2}$
  4. 1 : 2

Answer: (a)

Solution

In uniform magnetic field, $$R = \frac{mv}{qB} = \frac{\sqrt{2\, m\, (\mathrm{K.E})}}{qB}$$ Since same K.E $$R \propto \frac{\sqrt{m}}{q}$$ $$\therefore \frac{R_{deutron}}{R_{proton}} = \sqrt{\frac{m_d}{m_p}} \times \frac{q_p}{q_d}$$ $$= \sqrt{2} \times 1$$ $$\therefore \gamma_d : \gamma_p = \sqrt{2} : 1$$

Question 45

Physics · Dual Nature of Radiation and Matter · Single correct

UV light of $4.13\,\mathrm{eV}$ is incident on a photosensitive metal surface having work function $3.13\,\mathrm{eV}$. The maximum kinetic energy of ejected photoelectrons will be:

  1. 4.13 eV
  2. 3.13 eV
  3. 1 eV
  4. 7.26 eV

Answer: (c)

Solution

Given $E_{photon} = (work function) + K \cdot E_{\max}$. Therefore, $4.13 = 3.13 + K \cdot E_{\max}$. Thus, $K_{\max} = 1 \, eV$.

Question 46

Physics · Nuclei · Single correct

The energy released in the fusion of 2 kg of hydrogen deep in the sun is $E_H$ and the energy released in the fission of 2 kg of $^{235}\mathrm{U}$ is $E_U$. The ratio $\frac{E_H}{E_U}$ is approximately: (Consider the fusion reaction as $4\, ^1_1\mathrm{H} + 2e^- \rightarrow \, ^4_2\mathrm{He} + 2\nu + 6\gamma + 26.7\, \mathrm{MeV}$, energy released in the fission reaction of $^{235}\mathrm{U}$ is $200\, \mathrm{MeV}$ per fission nucleus and $N_A = 6.023 \times 10^{23}$)

  1. 7.62
  2. 25.6
  3. 15.04
  4. 9.13

Answer: (a)

Solution

In each fusion reaction, $^4_1 \mathrm{H}$ nucleus are used. Energy released per Nuclei of $^1_1 \mathrm{H} = \frac{26.7}{4} \mathrm{MeV}$. Therefore, energy released by $2 \mathrm{kg}$ hydrogen ($E_H$) is $$= \frac{2000}{1} \times N_A \times \frac{26.7}{4} \mathrm{MeV}$$ and energy released by $2 \mathrm{kg}$ Uranium ($E_V$) is $$= \frac{2000}{235} \times N_A \times 200 \mathrm{MeV}$$ So, $$\frac{E_H}{E_V} = 235 \times \frac{26.7}{4 \times 200} = 7.84$$ Therefore, approximately close to $7.62$.

Question 47

Physics · Thermodynamics · Single correct

A real gas within a closed chamber at 27^$\circ$ $\mathrm{C}$ undergoes the cyclic process as shown in figure. The gas obeys $PV^3 = RT$ equation for the path $A$ to $B$. The net work done in the complete cycle is (assuming $R = 8 \, \mathrm{J/molK}$):

  1. 20 $\mathrm{J}$
  2. 205 $\mathrm{J}$
  3. -20 $\mathrm{J}$
  4. 225 $\mathrm{J}$

Answer: (b)

Solution

Given $W_{AB} = \int \mathrm{PdV}$ (Assuming $T$ to be constant) $$= \int \frac{\mathrm{RTdV}}{V^3}$$ $$= \mathrm{RT} \int_2^4 V^{-3} \mathrm{dV}$$ $$= 8 \times 300 \times \left( -\frac{1}{2} \left[ \frac{1}{4^2} - \frac{1}{2^2} \right] \right)$$ $$= 225 \, \mathrm{J}$$ $W_{BC} = \mathrm{P} \int_4^2 \mathrm{dV} = 10(2 - 4) = -20 \, \mathrm{J}$ $W_{CA} = 0$ Therefore, $W_{cycle} = 205 \, \mathrm{J}$

Question 48

Physics · Laws of Motion · Single correct

A 1 kg mass is suspended from the ceiling by a rope of length 4 m. A horizontal force ' F ' is applied at the mid point of the rope so that the rope makes an angle of $45^\circ$ with respect to the vertical axis as shown in figure. The magnitude of $F$ is : (Assume that the system is in equilibrium and $g = 10 \, \mathrm{m/s^2}$ )

  1. 10 $\mathrm{N}$
  2. $\frac{10}{\sqrt{2}}$ $\mathrm{N}$
  3. 1 $\mathrm{N}$
  4. $\frac{1}{10 \times \sqrt{2}}$ $\mathrm{N}$

Answer: (a)

Solution

Given $T_1 \sin 45^\circ = F$. $T_1 \cos 45^\circ = T_2 = 1 \times g$. Therefore, $\tan 45^\circ = \frac{F}{g}$. Thus, $F = 10 \, \mathrm{N}$.

Question 49

Physics · Mechanical Properties of Fluids · Single correct

A spherical ball of radius $1 \times 10^{-4} \, \mathrm{m}$ and density $10^5 \, \mathrm{kg/m^3}$ falls freely under gravity through a distance $h$ before entering a tank of water, If after entering in water the velocity of the ball does not change, then the value of $h$ is approximately: (The coefficient of viscosity of water is $9.8 \times 10^{-6} \, \mathrm{N \, s/m^2}$ )

  1. 2296 m
  2. 2518 m
  3. 2249 m
  4. 2396 m

Answer: (b)

Solution

Given $$V_T = \frac{2}{9} g \frac{R^2 [\rho_B - \rho_L]}{\eta}$$ We have $$\Rightarrow V_T = \frac{2}{9} \times \frac{10 \times (10^{-4})^2}{9.8 \times 10^{-6}} \left[10^5 - 10^3\right]$$ This simplifies to $$\Rightarrow V_T = 224.5$$ When the ball falls from height $h$, $$V = \sqrt{2gh}$$ Thus, $$h = \left(\frac{V^2}{2g}\right) = 2518 \, \mathrm{m}$$

Question 50

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

In the truth table of the above circuit the value of X and Y are :

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

Answer: (b)

Solution

For x, when 0 is A and 1 is B, the output E is 1. For y, when 1 is A and 0 is B, the output E is 1.

Question 51

Physics · Moving Charges and Magnetism · Numerical

A straight magnetic strip has a magnetic moment of $44 \, \mathrm{Am}^2$. If the strip is bent in a semicircular shape, its magnetic moment will be ______ $\mathrm{Am}^2$. (given $\pi = \frac{22}{7}$)

Answer: 28

Solution

Magnetic moment of straight wire $= m x \ell = 44$. Magnetic moment of arc $$= m \times 2r$$ $$= m \times \frac{2\ell}{\pi}$$ $$= \frac{44 \times 2}{\pi} = \frac{88}{\pi} = 28$$

Question 52

Physics · Oscillations · Numerical

A particle of mass 0.50 kg executes simple harmonic motion under force $F = -50 \, (\mathrm{Nm}^{-1}) \, x$. The time period of oscillation is $\frac{x}{35}$ s. The value of $x$ is ______ (Given $\pi = \frac{22}{7}$)

Answer: 22

Solution

Given: $$m = 0.5 \, \mathrm{kg}$$ $$F = -50(x)$$ Using Newton's second law: $$ma = (-50x)$$ Substituting the value of $m$: $$0.5a = -50x$$ Solving for $a$: $$a = (-100x)$$ Given $W^2 = 100$, we find $w$: $$W^2 = 100 \implies (w = 10)$$ Now, calculating $T$: $$T = \frac{2\pi}{10} = \left(\frac{\pi}{5}\right) = \frac{22}{7 \times 15} = \left(\frac{22}{35}\right)$$ Equating: $$\frac{\pi}{35} = \frac{22}{35} \implies x = 22$$

Question 53

Physics · Alternating Current · Numerical

A capacitor of reactance $4\sqrt{3}\,\Omega$ and a resistor of resistance $4\,\Omega$ are connected in series with an ac source of peak value $8\sqrt{2}\,\mathrm{V}$. The power dissipation in the circuit is ________ W.

Answer: 4

Solution

Given $X_C = 4\sqrt{3} \, \Omega$ and $R = 4 \, \Omega$. The impedance $Z$ is given by $$Z = \sqrt{R^2 + X_L^2}$$ Substituting the values, $$Z = \sqrt{4^2 + (4\sqrt{3})^2} = 8 \, \Omega$$ The root mean square voltage $V_{rms}$ is $$V_{rms} = \frac{V}{\sqrt{2}} = \frac{8\sqrt{2}}{\sqrt{2}} = 8 \, V$$ The root mean square current $I_{rms}$ is $$I_{rms} = \frac{V_{rms}}{Z} = \frac{8}{8} = 1 \, A$$ The power dissipated is $$I_{rms}^2 \times R = 1 \times 4 = 4 \, W$$

Question 54

Physics · Electric Charges and Fields · Numerical

An electric field $\vec{E} = (2x\hat{i}) \, \mathrm{NC}^{-1}$ exists in space. A cube of side $2 \, \mathrm{m}$ is placed in the space as per figure given below. The electric flux through the cube is $\mathrm{Nm}^2/\mathrm{C}$.

Answer: 16

Solution

Given $\vec{E} = 2x \hat{i}$. The flux $\phi$ is given by $\vec{E} \cdot \vec{A}$. For $\phi_{in}$, we have $-4 \times 4 = -16 \, \mathrm{Nm^2/c}$. For $\phi_{out}$, we have $8 \times 4 = 32 \, \mathrm{Nm^2/c}$. The net flux $d_{net}$ is $\phi_{in} + \phi_{out} = -16 + 32 = 16 \, \mathrm{Nm^2/c}$.

Question 55

Physics · System of Particles and Rotational Motion · Numerical

A circular disc reaches from top to bottom of an inclined plane of length $l$. When it slips down the plane, if takes $t$ s. When it rolls down the plane then it takes ( $\frac{\alpha}{2}$)$^{1/2}$ t s, where $\alpha$ is

Answer: 3

Solution

For slipping $a = g \sin \theta$ $$\ell = \frac{1}{2} a t^2 \implies t = \sqrt{\frac{2 \ell}{g \sin \theta}}$$ For rolling $$a' = \frac{g \sin \theta}{1 + \frac{k^2}{R^2}} \left[ k = \frac{R}{\sqrt{2}} \right]$$ $$\implies a' = \frac{2 \, g \sin \theta}{3}$$ $$\ell = \frac{1}{2} a' (t')^2$$ $$\implies t' = \sqrt{\frac{6 \ell}{2 \, g \sin \theta}} = \sqrt{\frac{\alpha}{2}} \sqrt{\frac{2 \ell}{g \sin \theta}}$$ $$\implies \alpha = 3$$

Question 56

Physics · Current Electricity · Numerical

To determine the resistance $(R)$ of a wire, a circuit is designed below. The $V - I$ characteristic curve for this circuit is plotted for the voltmeter and the ammeter readings as shown in figure. The value of $R$ is $\Omega$.

Answer: 2500

Solution

Given $\($ Req = $\frac{10^4 R}{10^4 + R}$ $\)$ $\($ E = 4V, I = 2mA $\)$ $\($ I = $\frac{E}{Req}$ $\Rightarrow$ 2 $\times$ 10^{-3} = $\frac{4 \left(10^4 + R\right)}{10^4 R}$ $\)$ $\($ $\Rightarrow$ 20R = 40000 + 4R $\)$ $\($ 16R = 40000 $\)$ $\($ R = 2500 $\Omega$ $\)$

Question 57

Physics · Mathematics in Physics · Numerical

The resultant of two vectors $\vec{A}$ and $\vec{B}$ is perpendicular to $\vec{A}$ and its magnitude is half that of $\vec{B}$. The angle between vectors $\vec{A}$ and $\vec{B}$ is ^$\circ$.

Answer: 150

Solution

Given $B \cos \theta = \frac{B}{2}$. Therefore, $\theta = 60^\circ$. So, the angle between $\vec{A}$ and $\vec{B}$ is $90^\circ + 60^\circ = 150^\circ$.

Question 58

Physics · Wave Optics · Numerical

Monochromatic light of wavelength 500 nm is used in Young's double slit experiment. An interference pattern is obtained on a screen. When one of the slits is covered with a very thin glass plate (refractive index = 1.5 ), the central maximum is shifted to a position previously occupied by the 4^{th} bright fringe. The thickness of the glass-plate is ___ $\mu$ $\mathrm{m}$.

Answer: 4

Solution

$(\mu-1)t=n\lambda$ $(1.5-1)t=4\times500\times10^{-9}\ \mathrm{m}$ $t=4000\times10^{-9}\ \mathrm{m}$ $t=4\mu \mathrm{m}$

Question 59

Physics · Work, Energy and Power · Numerical

A force $(3x^2 + 2x - 5) \, \mathrm{N}$ displaces a body from $x = 2 \, \mathrm{m}$ to $x = 4 \, \mathrm{m}$. Work done by this force is____ \, $\mathrm{J}$.

Answer: 26

Solution

The work done is given by the integral of force with respect to displacement. $$W = \int_{x_1}^{x_2} F\,dx$$ Substituting the given force function, we have: $$W = \int_{2}^{4} (3x^2 + 2x - 5)\,dx$$ Integrating the function, we get: $$W = \left[x^3 + x^2 - 5x\right]_{2}^{4}$$ Evaluating the definite integral, we find: $$W = \left[60 - 2\right]\,\mathrm{J} = 58\,\mathrm{J}$$

Question 60

Physics · Thermal Properties of Matter · Numerical

At room temperature $(27^\circ C)$, the resistance of a heating element is 50 $\Omega$. The temperature coefficient of the material is $2.4\times10^{-4}\,{}^\circ C^{-1}$. The temperature of the element, when its resistance is 62 $\Omega$, is _____ $^{\circ}$ $\mathrm{C}$.

Answer: 1027

Solution

Given the equation $R = R_0 (1 + \alpha \Delta T)$. Substitute the values: $$62 = 50 \left[1 + 2.4 \times 10^{-4} \Delta T \right]$$ Solve for $\Delta T$: $$\Delta T = 1000^\circ \mathrm{C}$$ Therefore, $$T - 27^\circ = 1000^\circ \mathrm{C}$$ So, $$T = 1027^\circ \mathrm{C}$$

Chemistry

Question 61

Chemistry · Structure of Atom · Single correct

The candela is the luminous intensity, in a given direction, of a source that emits monochromatic radiation of frequency ' $A$ ' $\times 10^{12}$ hertz and that has a radiant intensity in that direction of $\frac{1}{B}$ watt per steradian. 'A' and 'B' are respectively

  1. 540 and 683
  2. 450 and 683
  3. 450 and $\frac{1}{683}$
  4. 540 and $\frac{1}{683}$

Answer: (a)

Solution

The candela is the luminous intensity of a source that emits monochromatic radiation of frequency radiation of frequency $540 \times 10^{12} \, \mathrm{Hz}$ and has a radiant intensity in that direction of $\frac{1}{683} \, \mathrm{W/sr}$. It is unit of Candela.

Question 62

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

The correct stability order of the following resonance structures of $CH_3 - CH = CH - CHO$ is

  1. I > II > III
  2. II > III > I
  3. II > I > III
  4. III > II > I

Answer: (d)

Solution

CH_3-CH=CH-CH=O (III) Non Polar R.S. More No of covalent bond CH_3-$\overset{+}{CH}$-CH=CH$\overset{-}{O}$ (II) Having -ve charge on more electronegative atom CH_3-$\overset{-}{CH}$=CH-CH$\overset{+}{O}$ (I) Having -ve charge on less electronegative atom Stability order III > II > I

Question 63

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

Total number of stereo isomers possible for the given structure :

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

Answer: (d)

Solution

There are three stereo centers. So the number of stereoisomers is $2^3 = 8$.

Question 64

Chemistry · Chemical Bonding and Molecular Structure · Single correct

The correct increasing order for bond angles among $BF_3$, $PF_3$ and $ClF_3$ is:

  1. $BF_3 < PF_3 < ClF_3$
  2. $ClF_3 < PF_3 < BF_3$
  3. $PF_3 < BF_3 < ClF_3$
  4. $BF_3 = PF_3 < ClF_3$

Answer: (b)

Solution

Order of bond angle is $\mathrm{ClF_3} < \mathrm{PF_3} < \mathrm{BF_3}$

Question 65

Chemistry · Analytical Chemistry · Single correct

Match List I with List II Choose the correct answer from the options given below:

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

Answer: (d)

Solution

(A) $\mathrm{Br_2}$ water test is test of unsaturation in which reddish orange colour of bromine water disappears. (B) Alcohols given Red colour with ceric ammonium nitrate. (C) Phenol gives Violet colour with natural ferric chloride. (D) Aldehyde & Ketone give Yellow/Orange/Red Colour compounds with 2, 4-DNP i.e., 2, 4-Dinitrophenyl hydrazine.

Question 66

Chemistry · Co-ordination Compounds · Single correct

Match List I with List II Choose the correct answer from the options given below:

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

Answer: (d)

Solution

A-IV, B-III, C-I, D-II

Question 67

Chemistry · Co-ordination Compounds · Single correct

Match List I with List II Choose the correct answer from the options given below:

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

Answer: (a)

Solution

For the complex $\mathrm{K_2[Ni(CN)_4]}$, the oxidation state of nickel is $+2$. The electronic configuration of $\mathrm{Ni^{2+}}$ is $[\mathrm{Ar}]3d^8 4s^0$. Since $\mathrm{CN}$ is a strong field ligand, it causes pairing of electrons in the $3d$ orbitals. The pre-hybridization state of $\mathrm{Ni^{2+}}$ is shown with paired electrons in the $3d$ orbitals and empty $4s$ and $4p$ orbitals. The hybridization is $dsp^2$.

Question 68

Chemistry · Co-ordination Compounds · Single correct

The coordination environment of $\mathrm{Ca}^{2+}$ ion in its complex with $\mathrm{EDTA}^{4-}$ is:

  1. tetrahedral
  2. trigonal prismatic
  3. octahedral
  4. square planar

Answer: (c)

Solution

EDTA $^{4-}$ is a hexadentate ligand. $$[Ca(EDTA)]^{2-}$$ So the coordination environment is octahedral.

Question 69

Chemistry · Biomolecules · Single correct

The incorrect statement about Glucose is :

  1. Glucose is soluble in water because of having aldehyde functional group
  2. Glucose remains in multiple isomeric form in its aqueous solution
  3. Glucose is one of the monomer unit in sucrose
  4. Glucose is an aldohexose

Answer: (a)

Solution

Glucose is soluble in water due to presence of alcohol functional group and extensive hydrogen bonding. Glucose exists in open chain as well as cyclic forms in its aqueous solution. Glucose has 6 carbon atoms so it is hexose and having an aldehyde functional group so it is aldose. Thus, aldohexose. Glucose is a monomer unit in sucrose with fructose.

Question 70

Chemistry · Aldehydes, Ketones and Carboxylic Acids · Single correct

In the above reaction product 'P' is

Answer: (d)

Solution

Question 71

Chemistry · Aldehydes, Ketones and Carboxylic Acids · Single correct

Which of the following compound can give positive iodoform test when treated with aqueous KOH solution followed by potassium hypoiodite.

Answer: (a)

Solution

The reaction starts with $\mathrm{CH_3 - CH_2 - CCl_2 - CH_3}$ treated with aqueous $\mathrm{KOH}$ to form $\mathrm{CH_3 - CH_2 - C(OH)_2 - CH_3}$. Upon dehydration, it forms $\mathrm{CH_3 - CH_2 - CO - CH_3}$. Further reaction with $\mathrm{KOI}$ leads to the formation of $\mathrm{CH_3 - CH_2 - COOK + CHI_3}$, where $\mathrm{CHI_3}$ is a yellow precipitate.

Question 72

Chemistry · Equilibrium · Single correct

For a sparingly soluble salt $AB_2$, the equilibrium concentrations of $A^{2+}$ ions and $B^{-}$ ions are $1.2 \times 10^{-4} \, \mathrm{M}$ and $0.24 \times 10^{-3} \, \mathrm{M}$, respectively. The solubility product of $AB_2$ is :

  1. $6.91 \times 10^{-12}$
  2. $0.276 \times 10^{-12}$
  3. $27.65 \times 10^{-12}$
  4. $0.069 \times 10^{-12}$

Answer: (a)

Solution

The equilibrium reaction is given by: $$\mathrm{AB_2}_{(s)} \rightleftharpoons \mathrm{A^{+2}}_{(aq)} + 2 \mathrm{B^-}_{(aq)}$$ The solubility product constant is: $$K_{sp} = [\mathrm{A^{+2}}][\mathrm{B^-}]^2$$ Substituting the given concentrations: $$= 1.2 \times 10^{-4} \times (2.4 \times 10^{-4})^2$$ Calculating the result: $$= 6.91 \times 10^{-12} \, \mathrm{M^3}$$

Question 73

Chemistry · Aldehydes, Ketones and Carboxylic Acids · Single correct

Major product of the following reaction is

Answer: (d)

Solution

.

Question 74

Chemistry · The d-and f-Block Elements · Single correct

Give below are two statements: Statement I : The higher oxidation states are more stable down the group among transition elements unlike p-block elements. Statement II : Copper can not liberate hydrogen from weak acids. 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

On moving down the group in transition elements, stability of higher oxidation state increases, due to increase in effective nuclear charge. $$\Rightarrow E^\circ_{\mathrm{Cu}^{+2}/\mathrm{Cu}} = 0.34 \, \mathrm{V}$$ $$\Rightarrow E^\circ_{\mathrm{H}^+/\mathrm{H}_2} = 0$$ SRP: $\mathrm{Cu}^{2+} > \mathrm{H}^+$ Cu can't liberate hydrogen gas from weak acid.

Question 75

Chemistry · Chemical Bonding and Molecular Structure · Single correct

The incorrect statement regarding ethyne is

  1. The C - C bonds in ethyne is shorter than that in ethene
  2. Both carbons are sp hybridised
  3. Ethyne is linear
  4. The carbon - carbon bonds in ethyne is weaker than that in ethene

Answer: (d)

Solution

The carbon-carbon bonds in ethyne is stronger than that in ethene. (H - C $\equiv$ C - H) Ethyne is linear and carbon atoms are SP hybridised.

Question 76

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

Match List I with List II \begin{tabular}{|l|l|} \hline \textbf{List-I(Element)} & \textbf{List-II(Electronic configuration)} \\ \hline (A) N & (I) $[Ar]3 d^{10} 4 s^2 4p^5$ \\ \hline (B) S & (II) $[Ne]3 s^2 3p^4$ \\ \hline (C) Br & (III) $[He]2 s^2 2p^3$ \\ \hline (D) Kr & (IV) $[Ar]3 d^{10} 4 s^2 4p^6$\\ \hline \end{tabular}

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

Answer: (a)

Solution

Option (A) $^7 \mathrm{N} : [\mathrm{He}] 2s^2 2p^3$ Option (B) $^{16} \mathrm{S} : [\mathrm{Ne}] 2s^2 3p^4$ Option ($C$) $^{35} \mathrm{Br} : [\mathrm{Ar}] 3d^{10} 4s^2 4p^5$ Option (D) $^{36} \mathrm{Kr} : [\mathrm{Ar}] 3d^{10} 4s^2 4p^6$

Question 77

Chemistry · Co-ordination Compounds · Single correct

Match List I with List II Choose the correct answer from the options given below:

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

Answer: (b)

Solution

Melting point: $\mathrm{B} > \mathrm{Al} > \mathrm{Tl} > \mathrm{In} > \mathrm{Ga}$ Ionic radius $\left(\mathrm{M^{+3}/pm}\right)$: $\mathrm{Tl} > \mathrm{In} > \mathrm{Ga} > \mathrm{Al} > \mathrm{B}$ $\left(\Delta_{\mathrm{IEH}}\right)_1 \left[\frac{\mathrm{kJ}}{\mathrm{mol}}\right]$: $\mathrm{B} > \mathrm{Tl} > \mathrm{Al} \approx \mathrm{Ga} > \mathrm{In}$ Atomic radius (in pm): $\mathrm{Tl} > \mathrm{In} > \mathrm{Al} > \mathrm{Ga} > \mathrm{B}$

Question 78

Chemistry · Aldehydes, Ketones and Carboxylic Acids · Single correct

Which of the following compounds will give silver mirror with ammoniacal silver nitrate?

  1. A, B and C only
  2. C and D only
  3. B and C only
  4. A only

Answer: (a)

Solution

Apart from aldehyde, Formic acid $\mathrm{HCOOH}$ also gives silver mirror test with ammoniacal silver nitrate.

Question 79

Chemistry · Electrochemistry · Single correct

Which out of the following is a correct equation to show change in molar conductivity with respect to concentration for a weak electrolyte, if the symbols carry their usual meaning:

  1. $\Lambda_m - \Lambda_m^0 + AC^{\frac{1}{2}} = 0$
  2. $\Lambda_m^2 C - K_a \Lambda_m^{o2} + K_a \Lambda_m \Lambda_m = 0$
  3. $\Lambda_m^2 C + K_a \Lambda_m^{o2} - K_a \Lambda_m \Lambda_m^o = 0$
  4. $\Lambda_m - \Lambda_m^o - AC^{\frac{1}{2}} = 0$

Answer: (b)

Solution

The reaction is given by: $$\mathrm{HA(aq) \rightleftharpoons H^+(aq) + A^-(aq)}$$ The expression for $K_a$ is: $$K_a = \frac{\alpha^2 C}{1 - \alpha}$$ Rearranging gives: $$\alpha^2 C + K_a \alpha - K_a = 0$$ Substituting $\alpha = \frac{\lambda_m}{\lambda_m^\infty}$, we have: $$\left(\frac{\lambda_m}{\lambda_m^\infty}\right)^2 C + K_a \frac{\lambda_m}{\lambda_m^\infty} - K_a = 0$$ Simplifying, we get: $$\lambda_m^2 C + K_a \lambda_m \lambda_m^\infty - K_a (\lambda_m^\infty)^2 = 0$$

Question 80

Chemistry · Structure of Atom · Single correct

The electronic configuration of Einsteinium is : (Given atomic number of Einsteinium = 99)

  1. [$\mathrm{Rn}$]5f^{10}6d^7s^2
  2. [$\mathrm{Rn}$]5f^{13}6d^7s^2
  3. [$\mathrm{Rn}$]5f^{11}6d^7s^2
  4. [$\mathrm{Rn}$]5f^{12}6d^7s^2

Answer: (c)

Solution

Einsteinium (atomic No = 99) : $[\mathrm{Rn}] 5f^{11} 6d^0 7s^2$

Question 81

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

Number of oxygen atoms present in chemical formula of fuming sulphuric acid is ______.

Answer: 7

Solution

Fuming sulphuric acid is a mixture of conc. $\mathrm{H_2SO_4} + \mathrm{SO_3}$ or $\mathrm{H_2S_2O_7}$. So, Number of Oxygen atoms = 7

Question 82

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

A transition metal 'M' among Sc, Ti, V, Cr, Mn and Fe has the highest second ionisation enthalpy. The spin only magnetic moment value of $\mathrm{M}^{+}$ ion is $\ldots$ BM (Near integer) (Given atomic number Sc : 21, Ti : 22, V : 23, Cr : 24, Mn : 25, Fe : 26)

Answer: 6

Solution

Question 83

Chemistry · Solutions · Numerical

The vapour pressure of pure benzene and methyl benzene at $27^\circ \mathrm{C}$ is given as $80 \, \mathrm{Torr}$ and $24 \, \mathrm{Torr}$, respectively. The mole fraction of methyl benzene in vapour phase, in equilibrium with an equimolar mixture of those two liquids (ideal solution) at the same temperature is $\times 10^{-2}$ (nearest integer)

Answer: 23

Solution

Given $X_{methylbenzene} = 0.5$. $Y_{methylbenzene} = \frac{P_{methylbenzene}}{P_{total}}$. $Y_{methylbenzene} = \frac{0.5 \times 24}{0.5 \times 80 + 0.5 \times 24}$. $= \frac{12}{40 + 12} = 0.23 = 23 \times 10^{-2}$.

Question 84

Chemistry · Co-ordination Compounds · Numerical

Consider the following test for a group-IV cation. $\mathrm{M^{2+}}$ $\mathrm{+ H_2 S \rightarrow A \ (Black precipitate) + by product}$ $\mathrm{A + aqua regia \rightarrow B + NOCl + S + H_2O}$ $\mathrm{B + KNO_2 + CH_3COOH \rightarrow C + by product}$ The spin-only magnetic moment value of the metal complex C is _____ BM (Nearest integer)

Answer: 0

Solution

If $M^{+2} = \mathrm{Co}^{+2}$ then $$\mathrm{Co}^{+2} + \mathrm{H_2 S} \rightarrow \mathrm{CoS} (Black) + byproduct$$ $$\mathrm{CoS} + aqua regia \rightarrow \mathrm{CoCl_2} + \mathrm{NOCl} + \mathrm{S} + \mathrm{H_2O}$$ $$\mathrm{CoCl_2} + \mathrm{KNO_2} \xrightarrow{\mathrm{CH_3COOH}} k_3 \left[ \mathrm{Co(NO_2)_6} \right] + byproduct$$ $[\mathrm{C}] = \mathrm{Co}^{+3} \rightarrow 3d^6 \Rightarrow \mathrm{NO_2}$ is SFL so $\mathrm{Co} +3$ has zero unpaired $e^-$. $$\Rightarrow n = 0 \Rightarrow u = \sqrt{n(n+2)} = 0 \mathrm{B.M}$$

Question 85

Chemistry · Chemical Kinetics and Nuclear Chemistry · Numerical

Consider the following first order gas phase reaction at constant temperature $$\mathrm{A(g) \rightarrow 2\,B(g) + C(g)}$$ If the total pressure of the gases is found to be $200\,\mathrm{torr}$ after $23\,\mathrm{sec}$ and $300\,\mathrm{torr}$ upon the complete decomposition of A after a very long time, then the rate constant of the given reaction is \_\_\_\_ $\times 10^{-2}\,\mathrm{s^{-1}}$ (nearest integer) [Given: $\log_{10}(2) = 0.301$]

Answer: 3

Solution

The reaction is given by $\($ $\mathrm{A(g) \rightarrow 2 \, B(g) + C(g)}$ $\)$. The pressure at time $\($ t = 23 $\)$ is $\($ P_{23} = P_0 + 2x = 200 $\)$. The final pressure is $\($ P_$\infty$ = 3P_0 = 300 $\)$. The initial pressure is $\($ P_0 = 100 $\)$. The rate constant $\($ K $\)$ is given by $$ K = \frac{1}{t} \ln \frac{P_\infty - P_0}{P_\infty - P_t} $$ Substituting the values, we have $$ K = \frac{2.3}{23} \log \frac{300 - 100}{300 - 200} $$ Simplifying further, $$ K = \frac{2.3 \times 0.301}{23} = 0.0301 = 3.01 \times 10^{-2} \, \mathrm{sec^{-1}} $$

Question 86

Chemistry · Organic Chemistry — Some Basic Principles & Techniques · Numerical

In the given TLC, the distance of spot A & B are 5 cm & 7 cm, from the bottom of TLC plate, respectively. $R_f$ value of B is $x \times 10^{-1}$ times more than A. The value of $x$ is ______.

Answer: 15

Solution

The formula for the retention factor $R_f$ is given by: $$R_f = \frac{Distance moved by substance from base line}{Distance moved by solvent from base line}$$ For substance A: $$(R_f)_A = \frac{4}{8}$$ For substance B: $$(R_f)_B = \frac{6}{8}$$ The ratio of $R_f$ values is: $$\frac{(R_f)_B}{(R_f)_A} = \frac{6}{8} \times \frac{8}{4}$$ Simplifying gives: $$(R_f)_B = 1.5 (R_f)_A$$ Given $x = 15$.

Question 87

Chemistry · Structure of Atom · Numerical

Based on Heisenberg's uncertainty principle, the uncertainty in the velocity of the electron to be found within an atomic nucleus of diameter $10^{-15} \, \mathrm{m}$ is ________. $10^9 \, \mathrm{ms}^{-1}$ (nearest integer) [Given : mass of electron $= 9.1 \times 10^{-31} \, \mathrm{kg}$, Planck's constant $(h) = 6.626 \times 10^{-34} \, \mathrm{Js}$ (Value of $\pi = 3.14$)]

Answer: 58

Solution

Given $m \Delta V \cdot \Delta x = \frac{h}{4 \pi}$. $$\Delta V = \frac{6.626 \times 10^{-34}}{9.1 \times 10^{-31} \times 10^{-15} \times 4 \times 3.14}$$ $$= 57.97 \times 10^{9} \, \mathrm{m/sec}$$

Question 88

Chemistry · Hydrocarbons · Numerical

Number of compounds from the following which cannot undergo Friedel-Crafts reactions is: _______. toluene, nitrobenzene, xylene, cumene, aniline, chlorobenzene, m-nitroaniline, m-dinitrobenzene

Answer: 4

Solution

Compounds which cannot undergo Friedel Crafts reaction are nitrobenzene, m-nitroaniline, and m-dinitrobenzene. These compounds contain electron-withdrawing groups that deactivate the benzene ring, making it less reactive towards electrophilic aromatic substitution reactions like Friedel Crafts.

Question 89

Chemistry · Chemical Bonding and Molecular Structure · Numerical

Total number of electrons present in $(\pi^*)$ molecular orbitals of $\mathrm{O}_2$, $\mathrm{O}_2^+$ and $\mathrm{O}_2^-$ is .

Answer: 6

Solution

For $\mathrm{O_2}(16\mathrm{e}): (\sigma_{1s})^2 (\sigma^*_{1s})^2 (\sigma_{2s})^2 (\sigma^*_{2s})^2 (\sigma_{2p})^2 \left[ (\pi_{2p})^2 = (\pi_{2p})^2 \right], \left[ (\pi^*_{2p})^1 = (\mathrm{m}^*_{2p})^1 \right]$. Number of $\mathrm{e}^-$ present in $(\pi^*)$ of $\mathrm{O_2} = 2$. Number of $\mathrm{e}^-$ present in $(\pi^*)$ of $\mathrm{O_2}^+ = 1$. Number of $\mathrm{e}^-$ present in $(\pi^*)$ of $\mathrm{O_2}^- = 3$. So total $\mathrm{e}^-$ in $(\pi^*) = 2 + 1 + 3 = 6$.

Question 90

Chemistry · Thermodynamics · Numerical

When $\Delta H_{vap} = 30 \, \mathrm{kJ/mol}$ and $\Delta S_{vap} = 75 \, \mathrm{J \, mol^{-1} \, K^{-1}}$, then the temperature of vapour, at one atmosphere is \underline{\hspace{1cm}} \, \mathrm{K}.

Answer: 400

Solution

At equilibrium $\Delta G_{PT} = 0$ $$\Delta H_{vap} = T \Delta S_{vap}$$ $$30 \times 1000 = T \times 75$$ $$T = 400 \, \mathrm{K}$$