JEE Main 3 April 2025 Shift 1 question paper with solutions

JEE Main 3 April 2025 Shift 1: all 75 questions in paper order (Maths, Physics, Chemistry) with the answer key and worked solutions. Free to read; attempt it as a timed 3-hour mock test.

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Maths

Question 1

Maths · Matrices · Single correct

Let A be a matrix of order 3 $\times$ 3 and $|A| = 5$. If $|2 \mathrm{adj}(3 A \mathrm{adj}(2 A))| = 2^\alpha \cdot 3^\beta \cdot 5^\gamma$, $\alpha, \beta, \gamma \in \mathbb{N}$ then $\alpha + \beta + \gamma$ is equal to

  1. 25
  2. 26
  3. 27
  4. 28

Answer: (c)

Solution

Given $|2 adj(3A adj(2A))|$. We have $2^3 \cdot |3A adj(2A)|^2$. This becomes $2^3 \cdot (3^3)^2 \cdot |A|^2 \cdot |adj(2A)|^2$. Simplifying further, $2^3 \cdot 3^6 \cdot |A|^2 \cdot \left( |2A|^2 \right)^2$. This is $2^3 \cdot 3^6 \cdot |A|^2 \left[ (2^3)^2 \cdot |A|^2 \right]^2$. Simplifying, $2^3 \cdot 3^6 \cdot |A|^2 \cdot 2^{12} \cdot |A|^4$. This results in $2^{15} \cdot 3^6 \cdot |A|^6$. Finally, $2^{15} \cdot 3^6 \cdot 5^6 = 2^\alpha \cdot 3^\beta \cdot 5^\gamma$. Given $\alpha = 15$, $\beta = 6$, $\gamma = 6$. Thus, $\alpha + \beta + \gamma = 27$.

Question 2

Maths · Three Dimensional Geometry · Single correct

Let a line passing through the point (4, 1, 0) intersect the line $L_1; \frac{x-1}{2} = \frac{y-2}{3} = \frac{z-3}{4}$ at the point $A \ (\alpha, \beta, \gamma)$ and the line $L_2 : x - 6 = y = -z + 4$ at the point $B(a, b, c)$. Then $$\begin{vmatrix} 1 & 0 & 1 \\ \alpha & \beta & \gamma \\ a & b & c \end{vmatrix}$$ is equal to

  1. 8
  2. 16
  3. 12
  4. 6

Answer: (a)

Solution

Given the lines: $$L_1 = \frac{x-1}{2} = \frac{y-2}{3} = \frac{z-3}{4} = p$$ $$L_2 = \frac{x-6}{1} = \frac{y}{1} = \frac{z-4}{-1} = q$$ Point $A$ is given by $(2p+1, 3p+2, 4p+3)$ and point $B$ by $(q+6, q, 4-q)$. The direction ratios of $PA$ are $2p-3, 3p+1, 4p+3$. The direction ratios of $PB$ are $q+2, q-1, 4-q$. Equating the direction ratios: $$2p-3 = 3p+1 = 4p+3$$ $$q+2 = q-1 = 4-q$$ Solving these equations: For $p$: $$2p - 3 = 3p + 1 \Rightarrow p = -4$$ $$2p - 3q + 3 = 3p + 6p + q + 2$$ $$pq + rp + 4q - 1 = 0$$ $$12p - 3pq + 4 - q = 4pq + 3q - 4p - 3$$ $$7pq - 16p + 4q - 7 = 0$$ $$8p - 2pq - 12 + 3q = 4pq + 8p + 3q + 6$$ $$6pq = -18 \Rightarrow pq = -3$$ For $q$: $$8p + 4q = 4 \Rightarrow 2p + q = 1$$ $$-21 - 16p + 4q - 7 \Rightarrow 4p - q = -7$$ $$16p - 4q = -28 \therefore p = -1, q = 3$$ Thus, $A(-1, -1, -1)$ and $B(9, 3, 1)$. The determinant is: $$\begin{vmatrix} 1 & 0 & 0 \\ 1 & -1 & 0 \\ 9 & 3 & 1 \end{vmatrix} = 1(-1 + 9) = 8$$

Question 3

Maths · Complex Numbers and Quadratic Equations · Single correct

Let $\alpha$ and $\beta$ be the roots of $x^2 + \sqrt{3}x - 16 = 0$, and $\gamma$ and $\delta$ be the roots of $x^2 + 3x - 1 = 0$. If $P_n = \alpha^n + \beta^n$ and $Q_n = \gamma^n + \delta^n$, then $$\frac{P_{25} + \sqrt{3}P_{24}}{2P_{23}} + \frac{Q_{25} - Q_{23}}{Q_{24}}$$ is equal to

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

Answer: (c)

Solution

Given $x^2 + \sqrt{3}x - 16 = 0 < \beta$. For $P_n + \sqrt{3}P_{n-1} - 16P_{n-2} = 0$, $$P_{25} + \sqrt{3}P_{24} - 16P_{23} = 0$$ Thus, $$P_{25} + \sqrt{3}P_{24} = 8$$ $$2P_{23}$$ Similarly, $x^2 + 3x - 1 = 0 < \sum \gamma_\delta$ $Q_n = \gamma^n + \delta^n$ $$Q_{25} - Q_{23} = \gamma^{25} + \delta^{25} - \gamma^{23} - \delta^{23}$$ $$= \gamma^{23}(\gamma^2 - 1) + \delta^{23}(\delta^2 - 1)$$ $$= \gamma^{23}(-3\gamma) + \delta^{23}(-3\gamma)$$ $$= -3 \left[ \gamma^{24} + \delta^{24} \right]$$ $$= -3Q_{24}$$ Thus, $$Q_{25} - Q_{23} = -3$$ $$Q_{24}$$ $$\frac{P_{25} + \sqrt{3}P_{24}}{2P_{23}} + \frac{Q_{25} - Q_{23}}{Q_{24}} = 8 - 3 = 5$$

Question 4

Maths · Binomial Theorem · Single correct

The sum of all rational terms in the expansion of $(2 + \sqrt{3})^8$ is

  1. 16923
  2. 3763
  3. 33845
  4. 18817

Answer: (d)

Solution

Given $S = (2 + \sqrt{3})^8$. For sum of rational terms: $$= \binom{8}{0} (2)^8 + \binom{8}{2} (2)^6 \cdot (\sqrt{3})^2 + \binom{8}{4} (2)^4 (\sqrt{3})^4$$ $$+ \binom{8}{6} (2)^2 (\sqrt{3})^6 + \binom{8}{8} (\sqrt{3})^8$$ $$= 2^8 + 28 \times 2^6 \cdot 3 + 70 \cdot 2^4 \cdot 9 + 28 \cdot 2^2 \cdot 27 + 81$$ $$= 256 + 5376 + 10080 + 3024 + 81$$ $$= 18817$$

Question 5

Maths · Sets · Single correct

Let A = $\{$-3, -2, -1, 0, 1, 2, 3,$\}$. Let R be a relation on A defined by $xRy$ if and only if $0 \leq x^2 + 2y \leq 4$. Let $l$ be the number of elements in $R$ and $m$ be the minimum number of elements required to be added in $R$ to make it a reflexive relation. then $l + m$ is equal to

  1. 19
  2. 20
  3. 17
  4. 18

Answer: (d)

Solution

By given data $\overrightarrow{AB} + \overrightarrow{AC} = \overrightarrow{CB}$. Let pv of $\overrightarrow{A}$ are $\overrightarrow{O}$ then $\overrightarrow{AB} = \overrightarrow{B} - \overrightarrow{A}$. i.e. pv of $\overrightarrow{B} = -2\hat{i} - \hat{j} + \hat{k}$. $\overrightarrow{CA} = \overrightarrow{A} - \overrightarrow{C}$. i.e. pv of $\overrightarrow{C} = -(\hat{i} - 3\hat{j} - 5\hat{k})$. Now pv of centroid $\overrightarrow{G} = \frac{\overrightarrow{A} + \overrightarrow{B} + \overrightarrow{C}}{3} = \frac{\overrightarrow{0} + (2, -1, 1) + (-1, 3, 5)}{3}$. $\overrightarrow{G} = \frac{1}{3}(\hat{i} + 2\hat{j} + 6\hat{k})$. Now $\overrightarrow{AG} = \frac{1}{3}(\hat{i} + 2\hat{j} + 6\hat{k})$. $\Rightarrow |\overrightarrow{AG}|^2 = \frac{1}{9} \times 41$. $\overrightarrow{BG} = \left(\frac{1}{3} - 2\right)\hat{i} + \left(\frac{2}{3} + 1\right)\hat{j} + (2 - 1)\hat{k}$. $\Rightarrow |\overrightarrow{BG}|^2 = \frac{59}{9}$. $\overrightarrow{CG} = \left(\frac{1}{3} + 1\right)\hat{i} + \left(\frac{2}{3} - 3\right)\hat{j} + (2 - 5)\hat{k}$. $\Rightarrow |\overrightarrow{CG}|^2 = \frac{146}{9}$. Now $6 \left[|\overrightarrow{AG}|^2 + |\overrightarrow{BG}|^2 + |\overrightarrow{CG}|^2\right] = 6 \times \left[\frac{41}{9} + \frac{59}{9} + \frac{146}{9}\right] = 6 \times \frac{246}{9} = 164$.

Question 6

Maths · Conic Sections · Single correct

A line passing through the point P($\sqrt{5}$, $\sqrt{5}$) intersects the ellipse $\frac{x^2}{36}$ + $\frac{y^2}{25}$ = 1 at A and B such that (PA) $\cdot$ (PB) is maximum. Then 5 $(PA^2 + PB^2)$ is equal to :

  1. 218
  2. 377
  3. 290
  4. 338

Answer: (d)

Solution

Given ellipse is $\frac{x^2}{36} + \frac{y^2}{25} = 1$. Any point on line $AB$ can be assumed as $Q(\sqrt{5} + r \cos \theta, \sqrt{5} + r \sin \theta)$. Putting this in equation of ellipse, we get $$25(\sqrt{5} + r \cos \theta)^2 + 36(\sqrt{5} + r \sin \theta)^2 = 900$$ Simplifying, we get $$r^2 \left( 25 \cos^2 \theta + 36 \sin^2 \theta \right) + 2 \sqrt{5} r (25 \cos \theta + 36 \sin \theta) - 595 = 0$$ $|r| = \mathrm{PA}, \mathrm{PB}$. $$\mathrm{PA} \cdot \mathrm{PB} = 595 = \frac{595}{25 \cos^2 \theta + 36 \sin^2 \theta} = \frac{595}{25 + 11 \sin^2 \theta}$$ maximum, if $\sin^2 \theta = 0$. This means line $AB$ must be parallel to $x$-axis $\Rightarrow y_A = y_B = \sqrt{5}$. Putting $y = \sqrt{5}$ in equation of ellipse, we get $$\frac{x^2}{36} + \frac{1}{5} = 1 \Rightarrow x^2 = 36 \cdot \frac{4}{5}$$ Hence, $$\mathrm{PA}^2 + \mathrm{PB}^2 = \left( \sqrt{5} - \frac{12}{\sqrt{5}} \right)^2 + \left( \sqrt{5} + \frac{12}{\sqrt{5}} \right)^2 = 2 \left( 5 + \frac{144}{5} \right) = \frac{338}{5}$$ $$5 \left( \mathrm{PA}^2 + \mathrm{PB}^2 \right) = 338$$

Question 7

Maths · Sequences and Series · Single correct

The sum $1 + 3 + 11 + 25 + 45 + 71 + \ldots$ up to 20 terms, is equal to

  1. 7240
  2. 7130
  3. 6982
  4. 8124

Answer: (a)

Solution

Given sum is $$S_n = 1 + 3 + 11 + 25 + 45 + 71 + \ldots + T_n$$ First order differences are in A.P. Thus, we can assume that $$T_n = an^2 + bn + c$$ Solving $$\begin{cases} T_1 = 1 = a + b + c \\ T_2 = 3 = 4a + 2b + c \\ T_3 = 11 = 9a + 3b + c \end{cases}$$ we get $a = 3$, $b = -7$, $c = 5$ Hence, general term of given series is $$T_n = 3n^2 - 7n + 5$$ Hence, required sum equals $$\sum_{n=1}^{20} \left(3n^2 - 7n + 5\right) = 3 \left(\frac{20 \cdot 21 \cdot 41}{6}\right) - 7 \left(\frac{20 \cdot 21}{2}\right) + 5(20) = 7240$$

Question 8

Maths · Relations and Functions · Single correct

If the domain of the function $f(x) = \log_e \left( \frac{2x-3}{5+4x} \right) + \sin^{-1} \left( \frac{4+3x}{2-x} \right)$ is $[\alpha, \beta)$ then $\alpha^2 + 4\beta$ is equal to

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

Answer: (b)

Solution

Given function is $f(x) = \log \left( \frac{2x-3}{5+4x} \right) + \sin^{-1} \left( \frac{4+3x}{2-x} \right)$. For domain, the conditions are $$\frac{2x-3}{5+4x} > 0 and \left| \frac{4+3x}{2-x} \right| \leq 1$$ Now, $$\frac{2x-3}{5+4x} > 0 \Rightarrow x \in \left( -\infty, -\frac{5}{4} \right) \cup \left[ \frac{3}{2}, \infty \right)$$ and $$-1 \leq \frac{4+3x}{2-x} \leq 1$$ $$\Rightarrow \left( -1 \leq \frac{4+3x}{2-x} \right) \cap \left( \frac{4+3x}{2-x} \leq 1 \right)$$ $$\Rightarrow \left( \frac{6+2x}{2-x} \geq 0 \right) \cap \left( \frac{2+4x}{2-x} \leq 0 \right)$$ $$\Rightarrow \frac{6+2x}{2-x} \cdot \frac{2+4x}{2-x} \leq 0$$ $$\Rightarrow x \in \left[ -3, -\frac{1}{2} \right]$$ Hence, we get the domain of $f$ as $x \in \left[ -3, -\frac{5}{4} \right)$. This means that $\alpha = -3, \beta = -\frac{5}{4}$. Thus, $\alpha^2 + 4\beta = 9 - 5 = 4$.

Question 9

Maths · Binomial Theorem · Single correct

\[ \text{If } \sum_{r=1}^{9} \binom{r+3}{2^r} \cdot {}^{9}C_r = \alpha \left(\frac{3}{2}\right)^9 - \beta, \quad \alpha, \beta \in \mathbb{N}, \] \[ \text{then } (\alpha + \beta)^2 \text{ is equal to} \]

  1. 27
  2. 9
  3. 81
  4. 18

Answer: (c)

Solution

Given $\($ $\sum$_{r=1}^{9} $\left$( $\frac{r+3}{2^r}$ $\right$) $\cdot$ $\binom{9}{r}$ = $\alpha$ $\left$( $\frac{3}{2}$ $\right$)^9 - $\beta$, $\alpha$, $\beta$ $\in$ $\mathbb{N}$ $\)$. Now, $\[$ $\sum$_{r=1}^{9} $\left$( $\frac{r+3}{2^r}$ $\right$) $\cdot$ $\binom{9}{r}$ = $\sum$_{r=1}^{9} $\left$( $\frac{r}{2^r}$ $\right$) $\cdot$ $\binom{9}{r}$ + $\sum$_{r=1}^{9} $\left$( $\frac{3}{2^r}$ $\right$) $\cdot$ $\binom{9}{r}$ $\]$ $\[$ = $\sum$_{r=1}^{9} $\left$( $\frac{9}{2^r}$ $\right$) $\cdot$ $\binom{8}{r-1}$ + 3 $\sum$_{r=1}^{9} $\binom{9}{r}$ $\left$( $\frac{1}{2}$ $\right$)^r $\left$[ Using g $\binom{9}{r}$ = $\frac{9}{r}$ $\binom{8}{r-1}$ $\right$] $\]$ $\[$ = $\frac{9}{2}$ $\sum$_{r=1}^{9} $\binom{8}{r-1}$ $\left$( $\frac{1}{2}$ $\right$)^{r-1} + 3 $\left$( $\sum$_{r=0}^{9} $\binom{9}{r}$ $\left$( $\frac{1}{2}$ $\right$)^r - 1 $\right$) $\]$ $\[$ = $\frac{9}{2}$ $\left$( 1 + $\frac{1}{2}$ $\right$)^8 + 3 $\left$( $\left$( 1 + $\frac{1}{2}$ $\right$)^9 - 1 $\right$) $\]$ $\[$ = $\frac{9}{2}$ $\cdot$ $\left$( $\frac{3}{2}$ $\right$)^8 + 3 $\left$( $\frac{3}{2}$ $\right$)^9 - 3 = 6 $\cdot$ $\left$( $\frac{3}{2}$ $\right$)^9 - 3 $\]$ Hence, $\($ $\alpha$ = 6, $\beta$ = 3 $\)$ Thus $\($ ($\alpha$ + $\beta$)^2 = 81 $\)$

Question 10

Maths · Trigonometric Functions · Single correct

The number of solutions of the equation $2x + 3 \tan x = \pi$, $x \in [-2\pi, 2\pi] - \left\{ \pm \frac{\pi}{2}, \pm \frac{3\pi}{2} \right\}$ is

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

Answer: (b)

Solution

Given $\tan x = \frac{\pi}{3} - \frac{2x}{3}$. The graph shows the function and its intersections with the line $y = \frac{\pi}{3} - \frac{2x}{3}$. There are 5 solutions where the line intersects the tangent function.

Question 11

Maths · Determinants · Single correct

\[ \text{If } y(x) = \begin{vmatrix} \sin x & \cos x & \sin x + \cos x + 1 \\ 27 & 28 & 27 \\ 1 & 1 & 1 \end{vmatrix}, \quad x \in \mathbb{R}, \] \[ \text{then } \frac{d^2 y}{dx^2} + y \text{ is equal to} \]

  1. -1
  2. 28
  3. 27
  4. 1

Answer: (a)

Solution

Given the transformation $C_3 \to C_3 - C_1$, we have: $$y(x) = \begin{vmatrix} \sin x & \cos x & 1 + \cos x \\ 27 & 28 & 0 \\ 1 & 1 & 0 \end{vmatrix}$$ $$y(x) = -(1 + \cos x)$$ Differentiating $y$ with respect to $x$: $$\frac{dy}{dx} = \sin x$$ $$\frac{d^2y}{dx^2} = \cos x$$ The differential equation is: $$\frac{d^2y}{dx^2} + y = -1$$

Question 12

Maths · Differential Equations · Single correct

Let $g$ be a differentiable function such that $\int_0^x g(t) dt = x - \int_0^x tg(t) dt, x \geq 0$ and let $y = y(x)$ satisfy the differential equation $\frac{dy}{dx} - y \tan x = 2(x + 1) \sec x g(x), x \in \left[0, \frac{\pi}{2}\right)$. If $y(0) = 0$, then $y\left(\frac{\pi}{3}\right)$ is equal to

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

Answer: (b)

Solution

Differentiate with respect to $x$. Given $g(x) = 1 - xg(x)$, we have $$g(x) = \frac{1}{1 + x}$$ so $$\frac{dy}{dx} - y \tan x = 2 \sec x$$ The integrating factor is $$IF = e^{-\int \tan dx} = e^{\log \cos x} = \cos x$$ The solution of the differential equation is $$y \cos x = \int 2 dx + c$$ $$y \cos x = 2x + c$$ Given $y(0) = 0$, we find $$c = 0$$ Thus, $$y = \frac{2x}{\cos x}$$ $$y = 2x \sec x$$ Finally, $$y\left(\frac{\pi}{3}\right) = 2 \cdot \frac{\pi}{3} \cdot 2 = \frac{4\pi}{3}$$

Question 13

Maths · Straight Lines and Pair of Straight Lines · Single correct

A line passes through the origin and makes equal angles with the positive coordinate axes. It intersects the lines $L_1 : 2x + y + 6 = 0$ and $L_2 : 4x + 2y - p = 0, p > 0$, at the points $A$ and $B$, respectively. If $AB = \frac{9}{\sqrt{2}}$ and the foot of the perpendicular from the point $A$ on the line $L_2$ is $M$, then $\frac{AM}{BM}$ is equal to

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

Answer: (d)

Solution

Line is $y = x$. $m_1 = 1$, $m_2 = -2$. So $\tan \theta = \left| \frac{1 + 2}{1 - 2} \right|$. $\tan \theta = \frac{AM}{BM} = 3$.

Question 14

Maths · Complex Numbers and Quadratic Equations · Single correct

Let $z \in \mathbb{C}$ be such that $\frac{z^2 + 3i}{z - 2 + i} = 2 + 3i$. Then the sum of all possible values of $z^2$ is

  1. 19 - 2i
  2. -19 - 2i
  3. 19 + 2i
  4. -19 + 2i

Answer: (b)

Solution

Given $z^2 + 3i = z(2 + 3i) - 7 - 4i$. We have $$z^2 - z(2 + 3i) + 7 + 7i = 0$$ Then, $$z_1^2 + z_2^2 = (z_1 + z_2)^2 - 2z_1z_2$$ Calculating, $$= 4 - 9 + 12i - 14 - 14i$$ $$= -19 - 2i$$

Question 15

Maths · Integrals · Single correct

Let $f(x) = \int x^3 \sqrt{3} - x^2 \, dx$. If $5f(\sqrt{2}) = -4$, then $f(1)$ is equal to

  1. $-\frac{2\sqrt{2}}{5}$
  2. $-\frac{8\sqrt{2}}{5}$
  3. $-\frac{4\sqrt{2}}{5}$
  4. $-\frac{6\sqrt{2}}{5}$

Answer: (d)

Solution

Let $3 - x^2 = t^2$. Then $x \, dx = -t \, dt$. $$f(x) = \int (3 - t^2) \cdot t (-t \, dt) + c$$ $$= \int (t^4 - 3t^2) \, dt + c$$ $$= \frac{t^5}{5} - t^3 + c$$ $$f(x) = \frac{(3 - x^2)^{5/2}}{5} - (3 - x^2)^{3/2} + c$$ $$f(\sqrt{2}) = \frac{1}{5} - 1 + c = -\frac{4}{5}$$ Thus, $c = 0$. $$f(1) = \frac{2^{5/2}}{5} - 2^{3/2}$$ $$= 2^{1/2} \left( \frac{4}{5} - 2 \right)$$ $$f(1) = -\frac{6\sqrt{2}}{5}$$

Question 16

Maths · Sequences and Series · Single correct

Let $a_1, a_2, a_3, \ldots$ be a G. P. of increasing positive numbers. If $a_3 a_5 = 729$ and $a_2 + a_4 = \frac{111}{4}$, then $24 \left( a_1 + a_2 + a_3 \right)$ is equal to

  1. 131
  2. 130
  3. 129
  4. 128

Answer: (c)

Solution

Let the 1st term of G.P. be $a$ and common ratio be $r$. $$a_3 a_5 = ar^2 \cdot ar^4 = 729$$ $$= a^2 r^6 = 729$$ $$= ar^3 = 27 \ldots (i)$$ $$a_2 + a_4 = ar + ar^3 = \frac{111}{4}$$ $$= ar = \frac{3}{4} \ldots (ii)$$ Dividing (i) by (ii): $$ar^3 = 27$$ $$ar = \frac{3}{4}$$ $$r^2 = 36$$ $$r = 6$$ From (ii): $$a(6) = \frac{3}{4} \implies a = \frac{1}{8}$$ Now, $24 (a_1 + a_2 + a_3)$ $$= 24 \left(a + ar + a^2\right)$$ $$= 24a \left(1 + r + r^2\right)$$ $$= 24 \times \frac{1}{8} \left(1 + 6 + 36\right)$$ $$= 3(43)$$ $$= 129$$

Question 17

Maths · Applications of Integrals · Single correct

Let the domain of the function $f(x)=\log_2\log_4\log_6(3+4x-x^2)$ be $(a,b)$. If $\displaystyle\int_0^{b-a}[x^2]\,dx=p-\sqrt{q}-\sqrt{r}$, $p,q,r\in\mathbb{N}$, $\gcd(p,q,r)=1$, where $[\,\cdot\,]$ is the greatest integer function, then $p+q+r$ is equal to

  1. 10
  2. 8
  3. 11
  4. 9

Answer: (a)

Solution

Given $\log_4 \log_6 (3 + 4x - x^2) > 0$. (1) $\log_6 (3 + 4x - x^2) > 1$ $3 + 4x - x^2 > 6$ $x^2 - 4x + 3 < 0$ $(x - 1)(x - 3) < 0$ $x \in (1, 3)$ So $a = 1$ and $b = 3$. Therefore, $\int_0^2 \lfloor x^2 \rfloor \, dx = ?$ $I = \int_0^1 \lfloor x^2 \rfloor \, dx + \int_1^{\sqrt{2}} \lfloor x^2 \rfloor \, dx + \int_{\sqrt{2}}^{\sqrt{3}} \lfloor x^2 \rfloor \, dx + \int_{\sqrt{3}}^{\sqrt{4}} \lfloor x^2 \rfloor \, dx$ $= 0 + \lfloor x \rfloor \big|_1^{\sqrt{2}} + 2 \lfloor x \rfloor \big|_{\sqrt{3}}^{\sqrt{2}} + 3 \lfloor x \rfloor \big|_{\sqrt{4}}^{\sqrt{3}}$ $= (\sqrt{2} - 1) + 2(\sqrt{3} - \sqrt{2}) + 3(2 - \sqrt{3})$ $= 5 - \sqrt{2} - \sqrt{3} \Rightarrow p + q + r = 10$

Question 18

Maths · Conic Sections · Single correct

The radius of the smallest circle which touches the parabolas $y = x^2 + 2$ and $x = y^2 + 2$ is

  1. $\frac{7\sqrt{2}}{2}$
  2. $\frac{7\sqrt{2}}{16}$
  3. $\frac{7\sqrt{2}}{4}$
  4. $\frac{7\sqrt{2}}{8}$

Answer: (d)

Solution

Tangents at A and B must be parallel to the line $y = x$, so the slope of the tangents is $1$. $$\left( \frac{dy}{dx} \right)_{\min A} = 1 = \left( \frac{dy}{dx} \right)_{\min B}$$ For point B, $y = x^2 + 2$. $$\frac{dy}{dx} = 2x = 1$$ $$x = \frac{1}{2} \Rightarrow y = \frac{9}{4}$$ Therefore, $$Point B = \left( \frac{1}{2}, \frac{9}{4} \right) \Rightarrow Point A = \left( \frac{9}{4}, \frac{1}{2} \right)$$ $$AB = \sqrt{\left( \frac{1}{2} - \frac{9}{4} \right)^2 + \left( \frac{9}{4} - \frac{1}{2} \right)^2}$$ $$= \sqrt{\frac{98}{16}} = \frac{7\sqrt{2}}{4}$$ Radius $= \frac{7\sqrt{2}}{8}$

Question 19

Maths · Continuity and Differentiability · Single correct

Let $f(x)= \begin{cases} (1+ax)^{1/x}, & x 0. \end{cases}$ be continuous at $x=0$. Then $e^{a}bc$ is equal to

  1. 64
  2. 72
  3. 48
  4. 36

Answer: (c)

Solution

Given $f(0^-) = e^{\lim_{x \to 0} \frac{ax}{x}} = e^a$. $f(0) = 1 + b$ $f(0^+) = \frac{1}{3}(x + c)^{-\frac{2}{3}} = \frac{1}{3} \cdot c^{-\frac{2}{3}} = \frac{3}{4} c^{\frac{2}{3}}$ Also at $x = 0$; $c^{\frac{1}{3}} = 2 \Rightarrow c = 8$ So $f(0^+) = \frac{3}{4} (8)^{\frac{2}{3}} = 3$ Now, $e^a = b + 1 = 3$ $e^a \cdot b \cdot c = 3 \cdot 2 \cdot 8 = 48$

Question 20

Maths · Three Dimensional Geometry · Single correct

Line $L_1$ passes through the point $(1, 2, 3)$ and is parallel to $Z$-axis. Line $L_2$ passes through the point $(\lambda, 5, 6)$ and is parallel to $y$-axis. Let for $\lambda = \lambda_1, \lambda_2, \lambda_2 < \lambda_1$, the shortest distance between the two lines be $3$. Then the square of the distance of the point $(\lambda_1, \lambda_2, 7)$ from the line $L_1$ is

  1. 40
  2. 32
  3. 25
  4. 37

Answer: (c)

Solution

Given the lines: $$L_1 \equiv \frac{x-1}{0} = \frac{y-2}{0} = \frac{z-3}{1}$$ $$L_2 \equiv \frac{x-\lambda}{0} = \frac{y-5}{1} = \frac{z-6}{0}$$ The symmetric difference (SD) is given by: $$SD = \begin{vmatrix} \hat{i} & \hat{j} & \hat{k} \\ 0 & 0 & 1 \\ 0 & 1 & 0 \end{vmatrix}$$ This simplifies to: $$= |\lambda - 1| = 3$$ Solving gives: $$\lambda = 4, -2$$ Letting $\lambda_1 = 4$ and $\lambda_2 = -2$. Let the foot of the perpendicular from $P(4, -2, 7)$ be $Q(1, 2, t + 3)$. So, $\vec{PQ} = (3, -4, 4-t) \cdot (0, 0, 1) = 0$. Solving gives $t = 4$. Thus, $Q(1, 2, 7)$. The distance $PQ^2 = 9 + 16$. Therefore, $PQ^2 = 25$.

Question 21

Maths · Probability (Advanced) · Numerical

All five letter words are made using all the letters A, B, C, D, E and arranged as in an English dictionary with serial numbers. Let the word at serial number $n$ be denoted by $W_n$. Let the probability $P(W_n)$ of choosing the word $W_n$ satisfy $P(W_n) = 2P(W_{n-1}), \ n > 1$. If $P(CDBEA) = \frac{2^\alpha}{2^\beta - 1}, \ \alpha, \beta \in \mathbb{N}$, then $\alpha + \beta$ is equal to:

Answer: 183

Solution

Let $P(W_1) = x$. $$\sum_{i=1}^{120} P(W_i) = 1$$ $$x + 2x + 2^2 x + 2^3 x + \ldots + 2^{119} x = 1$$ $$x (2^{120} - 1) = 1 \Rightarrow x = \frac{1}{2^{120} - 1} \ldots (i)$$ Rank of CDBEA $$A\_\_\_\_ = \underline{4} = 24$$ $$B\_\_\_\_ = \underline{4} = 24$$ $$CA\_\_\_ = \underline{3} = 6$$ $$CB\_\_\_ = \underline{3} = 6$$ $$CDA\_\_ = \underline{2} = 2$$ $$64$$ CDBAE = 1 CDBEA = 1 So, $P(W_{64}) = 2P(W_{63}) = \ldots = 2^{63} P(W_1)$ $$= \frac{2^{63}}{2^{120} - 1}$$ $$\alpha + \beta = 63 + 120 = 183$$

Question 22

Maths · Conic Sections · Numerical

Let the product of the focal distances of the point $P(4, 2\sqrt{3})$ on the hyperbola $H: \frac{x^2}{a^2} - \frac{y^2}{b^2} = 1$ be $32$. Let the length of the conjugate axis of $H$ be $p$ and the length of its latus rectum be $q$. Then $p^2 + q^2$ is equal to

Answer: 120

Solution

Given $\($ $\frac{x^2}{a^2}$ - $\frac{y^2}{b^2}$ = 1 $\)$ $\ldots$ (1) Point $\($ P(4, 2$\sqrt{3}$) $\)$ $\($ PS_1 $\cdot$ PS_2 = 32 $\)$ $\($|PS_1 - PS_2| = 2a $\)$ Point $\($ P(4, 2$\sqrt{3}$) $\)$ lies on $\($ H $\)$ $\($ $\frac{16}{a^2}$ - $\frac{12}{b^2}$ = 1 $\)$ $\($ 16b^2 - 12a^2 = a^2b^2 $\)$ $\ldots$ (2) $\($|PS_1 - PS_2|^2 = 4a^2 $\)$ $\($ PS_1^2 + PS_2^2 - 2PS_1 $\cdot$ PS_2 = 4a^2 $\)$ $\($ (ae - 4)^2 + 12 + (ae + 4)^2 + 12 - 64 = 4a^2 $\)$ $\($ 2a^2e^2 - 8 = 4a^2 $\)$ $\($ a^2 + b^2 - 4 = 4a^2 $\)$ $\($ b^2 - a^2 = 4 $\)$ From (2) and (3) $\($ $\Rightarrow$ 16(a^2 + 4) - 12a^2 = a^2(a^2 + 4) $\)$ $\($ $\Rightarrow$ 16a^2 + 64 - 12a^2 = a^4 + 4a^2 $\)$ $\($ $\Rightarrow$ a^4 = 64 $\)$ $\($ $\Rightarrow$ a^2 = 8 $\)$ Thus, $\($ b^2 = 12 $\)$ $\($ p^2 + q^2 = 4b^2 + $\frac{4b^4}{a^2}$ $\)$ $\($ = 120 $\)$

Question 23

Maths · Vector Algebra · Fill in the blank

Let $\vec{a} = \hat{i} + \hat{j} + \hat{k}$, $\vec{b} = 3\hat{i} + 2\hat{j} - \hat{k}$, $\vec{c} = \lambda \hat{j} + \mu \hat{k}$ and $\hat{d}$ be a unit vector such that $\vec{a} \times \hat{d} = \vec{b} \times \hat{d}$ and $\vec{c} \cdot \hat{d} = 1$, If $\vec{c}$ is perpendicular to $\vec{a}$, then $|3\lambda \hat{d} + \mu \vec{c}|^2$ is equal to _____.

Answer: 5

Solution

Given $\vec{a} \times \vec{d} - \vec{b} \times \vec{d} = 0$. $\left( \vec{a} - \vec{b} \right) \times \vec{d} = 0$. $\vec{d} = t(\vec{a} - \vec{b})$. $\vec{d} = t(-2\hat{i} - \hat{j} + 2\hat{k})$. $|\vec{d}| = 1$. $|t| = \frac{1}{3}$. $\vec{c} \cdot \vec{a} = 0$. $\lambda + \mu = 0$. $\mu = -\lambda$. $\vec{c} = \lambda(\hat{j} - \hat{k}), \ |\vec{c}|^2 = 2\lambda^2$. $\vec{c} \cdot \hat{d} = 1$. $t(-2, -1, 2) \cdot \lambda(0, 1, -1) = 1$. $\lambda t = \frac{-1}{3} \Rightarrow \lambda^2 = 1$. $|3\lambda \hat{d} + \mu \vec{c}|^2 = 9\lambda^2 |\hat{d}|^2 + \mu^2 |\vec{c}|^2 + 6\lambda \mu (\hat{d} \cdot \vec{c})$. $= 3\lambda^2 + 2\lambda^4$. $= 5$.

Question 24

Maths · Permutations and Combinations · Numerical

If the number of seven-digit numbers, such that the sum of their digits is even, is $m \cdot n \cdot 10^n$; $m, n \in \{1, 2, 3, \ldots, 9\}$, then $m + n$ is equal to

Answer: 14

Solution

Total 7 digit numbers = 9000000. 7 digit numbers having sum of digits even = 4500000 = 9.5 $\cdot$ 10^5. $m = 9$, $n = 5$. $m + n = 14$.

Question 25

Maths · Applications of Integrals · Numerical

The area of the region bounded by the curve $y = \max\{|x|, x|x - 2|\}$, then $x$-axis and the lines $x = -2$ and $x = 4$ is equal to ________.

Answer: 12

Solution

Required Area = $\frac{1}{2}$ $\times$ 2 $\times$ 2 + $\frac{1}{2}$ $\times$ 3 $\times$ 3 + $\frac{1}{2}$ $\times$ 1 $\times$ 11 = 12

Physics

Question 26

Physics · Thermal Properties of Matter · Single correct

During the melting of a slab of ice at 273 K at atmospheric pressure:

  1. Internal energy of ice-water system remains unchanged.
  2. Positive work is done by the ice-water system on the atmosphere.
  3. Internal energy of the ice-water system decreases.
  4. Positive work is done on the ice-water system by the atmosphere.

Answer: (d)

Solution

Volume decreases during melting of ice so positive work is done on ice water system by atmosphere. Heat absorbed by ice water so $\Delta Q$ is positive, work done by ice water system is negative. Hence by first law of thermodynamics $$\Delta U = \Delta Q + \Delta W = Positive$$ So internal energy increases.

Question 27

Physics · Mechanical Properties of Fluids · Single correct

Consider a completely full cylindrical water tank of height 1.6 m and cross-sectional area 0.5 $m^2$. It has a small hole in its side at a height 90 cm from the bottom. Assume, the cross-sectional area of the hole to be negligibly small as compared to that of the water tank. If a load 50 kg is applied at the top surface of the water in the tank then the velocity of the water coming out at the instant when the hole is opened is: (g = 10 $m/s^2$)

  1. 3 m/s
  2. 5 m/s
  3. 2 m/s
  4. 4 m/s

Answer: (d)

Solution

Apply Bernoulli equation between points 1 and 2 $$P_1 + \frac{1}{2} \rho v_1^2 + \rho gh = P_2 + \frac{1}{2} \rho v_2^2 + 0$$ $$P_0 + \frac{mg}{A} + \rho g \frac{70}{100} = P_0 + \frac{1}{2} \rho v_2^2$$ $$5000 + 0.5 \times 10^3 \times 10 \times \frac{70}{100} = \frac{1}{2} \times 10^3 v_2^2$$ $$10^3 + 10^3 \times 7 = \frac{1}{2} v_2^2$$ $$v_2^2 = 16$$ $$v_2 = 4 \, \mathrm{m/s}$$ As the tank area is large $v_1$ is negligible compared to $v_2$.

Question 28

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

Choose the correct logic circuit for the given truth table having inputs A and B. Inputs Output

Answer: (b)

Solution

Q5. Only option (2) matches with the truth table.

Question 29

Physics · Dual Nature of Radiation and Matter · Single correct

The radiation pressure exerted by a 450 W light source on a perfectly reflecting surface placed at 2 m away from it, is :

  1. 1.5 $\times$ $10^{-8}$ Pascals
  2. 0
  3. 6 $\times$ $10^{-8}$ Pascals
  4. 3 $\times$ $10^{-8}$ Pascals

Answer: (c)

Solution

Given $P_{rad} = \frac{2I}{C}$. Where $I =$ intensity at surface. $C =$ Speed of light. $$I = \frac{Power}{Area} = \frac{450}{4\pi^2}$$ $$= \frac{450}{4\pi \times 4} = \frac{450}{16\pi}$$ $$= \frac{2 \times 450}{16\pi \times 3 \times 10^8} = \frac{150}{8\pi \times 10^8}$$ $$= 5.97 \times 10^{-8} \approx 6 \times 10^{-8} Pascals$$

Question 30

Physics · Current Electricity · Single correct

A wire of length 25 m and cross-sectional area 5 $\mathrm{mm}^2$ having resistivity of $2 \times 10^{-6} \Omega \mathrm{m}$ is bent into a complete circle. The resistance between diametrically opposite points will be

  1. 12.5 $\Omega$
  2. 50 $\Omega$
  3. 100 $\Omega$
  4. 25 $\Omega$

Answer: (d)

Solution

Given $L = 25 \, \mathrm{m}$, $A = 5 \, \mathrm{mm^2} = 5 \times 10^{-6} \, \mathrm{m^2}$, $\rho = 2 \times 10^{-6} \, \Omega \, \mathrm{m}$. $R_{wire} = \frac{\rho L}{A} = \frac{2 \times 10^{-6} \times 25}{5 \times 10^{-6}} = 10$. $R_{eq} = \frac{R}{4} = \frac{10}{4} = 2.5 \, \Omega$. Answer does not match with NTA option.

Question 31

Physics · Oscillations · Multiple correct

Two blocks of masses $m$ and $M$, $(M > m)$, are placed on a frictionless table as shown in figure. A massless spring with spring constant $k$ is attached with the lower block. If the system is slightly displaced and released then $\mu =$ coefficient of friction between the two blocks. (A) The time period of small oscillation of the two blocks is $2\pi\sqrt{\frac{m+M}{k}}$ (B) The acceleration of the blocks is $a=\frac{kx}{m+M}$, (where $x$ is the displacement of the blocks from the mean position.) (C) The magnitude of the frictional force on the upper block is $\frac{m\mu|x|}{m+M}$. (D) The maximum amplitude of the upper block, if it does not slip, is $\frac{\mu(M+m)g}{k}$. (E) Maximum frictional force can be $\mu(M+m)g$. Choose the correct answer from the options given below:

  1. A, B, D Only
  2. B, C, D Only
  3. C, D, E Only
  4. A, B, C, D Only

Answer: (a)

Solution

(A) As both blocks moving together so Time period $= 2\pi \sqrt{\frac{M+m}{K}}$; where $m = M + m$. (1) $T = 2\pi \sqrt{\frac{M+m}{K}}$ (B) Let block is displaced by $x$ in $(+ve)$ direction so force on block will be in $(-ve)$ direction $F = -Kx$ $(M+m)a = -Kx$ $a = -\frac{Kx}{(M+m)}$ (C) As upper block is moving due to friction thus $f = ma = \frac{mKx}{(M+m)}$ (D) This option is like two block problem in friction for maximum amplitude, force on block is also maximum, for which both blocks are moving together. $KA = (M+m)a$ $a = \frac{KA}{(M+m)}$ $f = ma = \frac{mKA}{(M+m)}$ $f_{max} = f_{L} = \mu mg$ $f = \mu mg$ $\frac{mKA}{(M+m)} = \mu mg$ $A = \frac{\mu (M+m)g}{K}$ (E) Maximum friction can be $\mu mg$ as force is acting between blocks $\&$ normal force here is $mg$.

Question 32

Physics · Motion in a Straight Line · Single correct

Which of the following curves possibly represent one-dimensional motion of a particle? Choose the correct answer from options given below

  1. \quad A,\ B \text{ and } D \text{ only}
  2. \quad A,\ B \text{ and } C \text{ only}
  3. \quad A \text{ and } B \text{ only}
  4. \quad A,\ C \text{ and } D \text{ only}

Answer: (a)

Solution

For option (A) $\phi = kt + C$ it can be 1D motion. eg $\rightarrow x = A \sin \phi$ (SHM). For option (B) $v^2 + x^2 = constant$ yes 1D. For option (C) time can't be negative Not possible. For option (D) Possible. A, B $\&$ D only.

Question 33

Physics · Electrostatic Potential and Capacitance · Single correct

A parallel plate capacitor is filled equally (half) with two dielectrics of dielectric constant $\varepsilon_1$ and $\varepsilon_2$, as shown in figures. The distance between the plates is $d$ and area of each plate is $A$. If capacitance in first configuration and second configuration are $C_1$ and $C_2$ respectively, then $\frac{C_1}{C_2}$ is:

  1. $\frac{\varepsilon_1 \varepsilon_2}{(\varepsilon_1 + \varepsilon_2)^2}$
  2. $\frac{4 \varepsilon_1 \varepsilon_2}{(\varepsilon_1 + \varepsilon_2)^2}$
  3. $\frac{\varepsilon_1 \varepsilon_2}{\varepsilon_1 + \varepsilon_2}$
  4. $\frac{2 \varepsilon_0 (\varepsilon_1 + \varepsilon_2)}{2}$

Answer: (b)

Solution

Area of plate is $A$. Then $$C = \frac{\varepsilon_2 \varepsilon_0 A}{d/2} = \frac{2 \varepsilon_2 \varepsilon_0 A}{d}$$ $$C' = \frac{\varepsilon_1 \varepsilon_0 A}{d/2} = \frac{2 \varepsilon_1 \varepsilon_0 A}{d}$$ Let $C_0 = \frac{\varepsilon_0 A}{d}$. $$C = 2 \varepsilon_2 C_0$$ $$C' = 2 \varepsilon_1 C_0$$ $C$ and $C'$ are in series. $$C_1 = \frac{CC'}{C + C'} = \frac{4 \varepsilon_2 \varepsilon_1 C_0^2}{2 C_0 (\varepsilon_2 + \varepsilon_1)}$$ Here $C = \frac{\varepsilon_1 \varepsilon_0 A}{2d} = \frac{\varepsilon_1 C_0}{2}$. $$C' = \frac{\varepsilon_2 C_0}{2}$$ $C$ and $C'$ are in parallel. $$C_2 = C' + C = (\varepsilon_1 + \varepsilon_2) \frac{C_0}{2}$$ Thus $$\frac{C_1}{C_2} = \frac{2 \varepsilon_2 \varepsilon_1 C_0}{(\varepsilon_2 + \varepsilon_1) (\varepsilon_1 + \varepsilon_2) C_0}$$ $$= \frac{4 \varepsilon_2 \varepsilon_1}{(\varepsilon_2 + \varepsilon_1)^2}$$

Question 34

Physics · Gravitation · Single correct

Match the LIST-I with LIST-II \begin{tabular}{|l|l|} \hline \textbf{LIST-I} & \textbf{LIST-II} \\ \hline A. Gravitational constant & I. $[LT^{-2}]$ \\ \hline B. Gravitational potential energy & II. $[L^2T^{-2}]$ \\ \hline C. Gravitational potential & III. $[ML^2T^{-2}]$ \\ \hline D. Acceleration due to gravity & IV. $[M^{-1}L^3T^{-2}]$ \\ \hline \end{tabular} Choose the correct answer from the options given below

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

Answer: (a)

Solution

(A) $G = \frac{Fr^2}{m^2}$ $$[G] = \left[ \mathrm{MLT^{-2}} \right] \left[ \mathrm{L^2} \right] \left[ \mathrm{M^2} \right]^{-1} = \left[ \mathrm{M^{-1} L^3 T^{-2}} \right] (\mathrm{IV})$$ (B) P.E. $= mgh = \left[ \mathrm{MLT^{-2} L} \right]$ $$= \left[ \mathrm{ML^2 T^{-2}} \right] (\mathrm{III})$$ (C) Gravitational Potential $= \frac{GM}{r}$ $$= \left[ \mathrm{M^{-1} L^3 T^{-2}} \right] \left[ \mathrm{M} \right] \left[ \mathrm{L} \right]^{-1} = \left[ \mathrm{M^0 L^2 T^{-2}} \right] (\mathrm{II})$$ (D) Acceleration due to gravity $= [g] = \left[ \mathrm{LT^{-2}} \right] (\mathrm{I})$$

Question 35

Physics · System of Particles and Rotational Motion · Single correct

A force of 49 $\mathrm{N}$ acts tangentially at the highest point of a sphere (solid) of mass 20 $\mathrm{kg}$, kept on a rough horizontal plane. If the sphere rolls without slipping, then the acceleration of the center of the sphere is

  1. 3.5 $\,$ $\mathrm{m/s^2}$
  2. 0.35 $\,$ $\mathrm{m/s^2}$
  3. 2.5 $\,$ $\mathrm{m/s^2}$
  4. 0.25 $\,$ $\mathrm{m/s^2}$

Answer: (a)

Solution

Torque about bottom point $$F \times 2r = I \alpha$$ $$49 \times 2r = \frac{7}{5} m r^2 \alpha$$ $$14 = 4r \alpha$$ As sphere rolls without slipping $$a = r \alpha$$ $$a = \frac{14}{4} = \frac{7}{2} = 3.5 \, \mathrm{m/s^2}$$

Question 36

Physics · Kinetic Theory · Single correct

A piston of mass $M$ is hung from a massless spring whose restoring force law goes as $F = -kx^3$, where $k$ is the spring constant of appropriate dimension. The piston separates the vertical chamber into two parts, where the bottom part is filled with $'n'$ moles of an ideal gas. An external work is done on the gas isothermally (at a constant temperature $T$) with the help of a heating filament (with negligible volume) mounted in lower part of the chamber, so that the piston goes up from a height $L_0$ to $L_1$, the total energy delivered by the filament is (Assume spring to be in its natural length before heating)

  1. $3nRT \ln \left( \frac{L_1}{L_0} \right) + 2Mg(L_1 - L_0) + \frac{k}{3} (L_1^3 - L_0^3)$
  2. $nRT \ln \left( \frac{L_1}{L_0} \right) + \frac{Mg}{2} (L_1 - L_0) + \frac{k}{4} (L_1^4 - L_0^4)$
  3. $nRT \ln \left( \frac{L_1}{L_0} \right) + Mg(L_1 - L_0) + \frac{k}{4} (L_1^4 - L_0^4)$
  4. $nRT \ln \left( \frac{L_1}{L_0} \right) + Mg(L_1 - L_0) + \frac{3k}{4} (L_1^4 - L_0^4)$
Solution

Using WET, total energy supplied equals gravitational potential energy plus spring potential energy plus work done by gas. $$Mg \left( L_1 - L_0 \right) + \int_{L_0}^{L_1} k^3 \, dx + nRT \ln$$ $\[$ $\begin{bmatrix}$ L_1 & A $\\$ L_0 & A $\end{bmatrix}$ $\]$ plus $\($ W_{ext} = 0 $\)$ $$\frac{K}{4} \left[ x^4 \right]_{L_0}^{L_1} + Mg(L_1 - L_0) + \int_{L_0}^{L_1} kx^3 \, dx + nRT \ln$$ $\[$ $\begin{bmatrix}$ L_1 $\\$ L_0 $\end{bmatrix}$ $\]$ plus $\($ W_{ext} = 0 $\)$ $$\frac{k}{4} \left( L_1^4 - L_0^4 \right) + Mg \left( L_1 - L_0 \right) + nRT \ln$$ $\[$ $\begin{bmatrix}$ L_1 $\\$ L_0 $\end{bmatrix}$ $\]$ plus $\($ W_{ext} = 0 $\)$ $$W_{ext} = \frac{k}{4} \left( L_1^4 - L_0^4 \right) + Mg(L_1 - L_0) + nRT \ln$$ $\[$ $\begin{bmatrix}$ L_1 $\\$ L_0 $\end{bmatrix}$ $\]$

Question 37

Physics · Kinetic Theory · Single correct

A gas is kept in a container having walls which are thermally non-conducting. Initially the gas has a volume of $800 \, \mathrm{cm}^3$ and temperature $27^\circ \mathrm{C}$. The change in temperature when the gas is adiabatically compressed to $200 \, \mathrm{cm}^3$ is: (Take $\gamma = 1.5$: $\gamma$ is the ratio of specific heats at constant pressure and at constant volume)

  1. 327 K
  2. 600 K
  3. 522 K
  4. 300 K

Answer: (d)

Solution

Given $V_1 = 800 \, \mathrm{cm}^3$, $V_2 = 200 \, \mathrm{cm}^3$, $T_1 = 300 \, \mathrm{K}$. For adiabatic process, $TV^{\gamma - 1} = const.$ $$(300)(800)^{1.5 - 1} = T_2(200)^{1.5 - 1}$$ $$T_2 = 300 \left[ \frac{800}{200} \right]^{0.5} = 300 \times (2^2)^{1/2}$$ $$T_2 = 600 \, \mathrm{K}$$ $$\Delta T = 600 - 300 = 300 \, \mathrm{K}$$

Question 38

Physics · Current Electricity · Single correct

Match the LIST-I with LIST-II Choose the correct option from the options given below:

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

Answer: (b)

Solution

Conceptual (2)

Question 39

Physics · Electric Charges and Fields · Single correct

The electrostatic potential on the surface of uniformly charged spherical shell of radius $R = 10 \, \mathrm{cm}$ is $120 \, \mathrm{V}$. The potential at the centre of shell, at a distance $r = 5 \, \mathrm{cm}$ from centre, and at a distance $r = 15 \, \mathrm{cm}$ from the centre of the shell respectively, are:

  1. $120 \, \mathrm{V}, 120 \, \mathrm{V}, 80 \, \mathrm{V}$
  2. $40 \, \mathrm{V}, 40 \, \mathrm{V}, 80 \, \mathrm{V}$
  3. $0 \, \mathrm{V}, 0 \, \mathrm{V}, 80 \, \mathrm{V}$
  4. $0 \, \mathrm{V}, 120 \, \mathrm{V}, 40 \, \mathrm{V}$

Answer: (a)

Solution

Potential inside shell is equal to potential on surface. $$V_{in} = V_{surface} = \frac{kQ}{R} = 120 \, \mathrm{V}$$ at $r = 15 \, \mathrm{cm}$ $$V = \frac{kQ}{r} = \frac{120 \times 10}{15} = 80 \, \mathrm{V}$$

Question 40

Physics · Dual Nature of Radiation and Matter · Single correct

The work function of a metal is $3 \, \mathrm{eV}$. The color of the visible light that is required to cause emission of photoelectrons is

  1. Green
  2. Blue
  3. Red
  4. Yellow

Answer: (b)

Solution

Given $(KE)_{\max} = \frac{hc}{\lambda} - \phi$. For emission, $\frac{hc}{\lambda} > \phi$. This implies $\lambda < \frac{hc}{\phi} \Rightarrow \lambda < \frac{1242}{3} \, \mathrm{nm}$. So blue light option (B) is correct.

Question 41

Physics · Gravitation · Single correct

A particle is released from height $S$ above the surface of the earth. At certain height its kinetic energy is three times its potential energy. The height from the surface of the earth and the speed of the particle at that instant are respectively.

  1. $\frac{S}{2}, \sqrt{\frac{3gS}{2}}$
  2. $\frac{S}{2}, \frac{3gS}{2}$
  3. $\frac{S}{4}, \frac{3gS}{2}$
  4. $\frac{S}{4}, \sqrt{\frac{3gS}{2}}$

Answer: (d)

Solution

Given $V^2 = 0 + 2g(S - x)$. $V^2 = 2g(S - x)$. At B, potential energy $= mgx$. $$mgx = 3 \times \frac{1}{2} mv^2$$ $$gx = \frac{3}{2} \times 2g(S - x)$$ $$4x = S$$ $$x = \frac{S}{4}$$ Therefore, $$V = \sqrt{2g \times \frac{3S}{4}} = \sqrt{\frac{3gS}{2}}$$

Question 42

Physics · Physical World, Units and Measurements · Single correct

A person measures mass of 3 different particles as $435.42 \, \mathrm{g}$, $226.3 \, \mathrm{g}$ and $0.125 \, \mathrm{g}$. According to the rules for arithmetic operations with significant figures, the additions of the masses of 3 particles will be.

  1. $661.845 \, \mathrm{g}$
  2. $662 \, \mathrm{g}$
  3. $661.8 \, \mathrm{g}$
  4. $661.84 \, \mathrm{g}$

Answer: (c)

Solution

Given $m_1 + m_2 + m_3 = 435.42 + 226.3 + 0.125$. According to least significant digits $m = 661.8 \, \mathrm{g}$.

Question 43

Physics · Ray Optics and Optical Instruments · Single correct

The radii of curvature for a thin convex lens are 10 cm and 15 cm respectively. The focal length of the lens is 12 cm. The refractive index of the lens material is

  1. 1.2
  2. 1.4
  3. 1.5
  4. 1.8

Answer: (c)

Solution

Given $\($ $\frac{1}{f}$ = ($\mu$ - 1) $\left$( $\frac{1}{R_1}$ - $\frac{1}{R_2}$ $\right$) $\)$ $\($ $\frac{1}{12}$ = ($\mu$ - 1) $\left$( $\frac{1}{10}$ - $\frac{1}{-15}$ $\right$) $\)$ $\($ $\frac{1}{12}$ = ($\mu$ - 1) $\left$( $\frac{3 + 2}{30}$ $\right$) $\)$ $\($ $\mu$ = $\frac{3}{2}$ $\)$

Question 44

Physics · Motion in a Plane · Single correct

The angle of projection of a particle is measured from the vertical axis as $\phi$ and the maximum height reached by the particle is $h_m$. Here $h_m$ as function of $\phi$ can be presented as.

Answer: (c)

Solution

The maximum height $H_{max}$ of a projectile launched at an angle $\theta$ with initial velocity $u$ is given by: $$H_{max} = \frac{u^2 \cos^2 \phi}{2g}.$$

Question 45

Physics · Ray Optics and Optical Instruments · Single correct

Consider following statements for refraction of light through prism, when angle of deviation is minimum. (A) The refracted ray inside prism becomes parallel to the base. (B) Larger angle prisms provide smaller angle of minimum deviation. (C) Angle of incidence and angle of emergence becomes equal. (D) There are always two sets of angle of incidence for which deviation will be same except at minimum deviation setting. (E) Angle of refraction becomes double of prism angle. Choose the correct answer from the options given below.

  1. B, C and D Only
  2. A, B and E Only
  3. B, D and E Only

Answer: (a)

Solution

Given $\delta = I + e - A$. For $\delta_{\min} \Rightarrow I = e$ and refracted ray is parallel to base. A, C, D are correct.

Question 46

Physics · Gravitation · Numerical

Three identical spheres of mass $m$, are placed at the vertices of an equilateral triangle of length $a$. When released, they interact only through gravitational force and collide after a time $T = 4$ seconds. If the sides of the triangle are increased to length $2a$ and also the masses of the spheres are made $2m$, then they will collide after _____ seconds.

Answer: 8

Solution

Given $T \propto m^x G^y a^z$. $T \propto M^x \left[ M^{-1} L^3 T^{-2} \right]^y \left[ L \right]^z$. $T \propto M^{x-y} L^{3y+z} T^{-2y}$. $x - y = 0 \Rightarrow x = y$. $-2y = 1 \Rightarrow y = -\frac{1}{2}, x = -\frac{1}{2}$. $\Rightarrow 3y + z = 0$. $z = -3y = \frac{3}{2}$. Hence $T \propto m^{-1/2} G^{-1/2} a^{3/2}$. $T \propto \left( \frac{a^3}{m} \right)^{1/2}$. $T = 4 \times \left( \frac{2^3}{2} \right)^{1/2} = 8 \, \mathrm{s}$.

Question 47

Physics · Moving Charges and Magnetism · Fill in the blank

A 4.0 cm long straight wire carrying a current of 8A is placed perpendicular to an uniform magnetic field of strength 0.15 T. The magnetic force on the wire is ______ mN.

Answer: 48

Solution

Given $F = I \ell B$. $$F = 8 \times \frac{4}{100} \times 0.15$$ $$= 48 \times 10^{-3} \, \mathrm{N} = 48 \, \mathrm{mN}$$

Question 48

Physics · Wave Optics · Numerical

Two coherent monochromatic light beams of intensities $4I$ and $9I$ are superimposed. The difference between the maximum and minimum intensities in the resulting interference pattern is $xI$. The value of $x$ is ______.

Answer: 24

Solution

Given $$I_{max} = \left( \sqrt{I_1} + \sqrt{I_2} \right)^2$$ $$= (\sqrt{4I} + \sqrt{9I})^2 = 25I$$ $$I_{min} = \left( \sqrt{I_1} - \sqrt{I_2} \right)^2$$ $$= (\sqrt{4I} - \sqrt{9I})^2 = I$$ $$I_{max} - I_{min} = 24I$$ $$x = 24$$

Question 49

Physics · Moving Charges and Magnetism · Fill in the blank

A loop ABCDA, carrying current $I = 12 \, \mathrm{A}$, is placed in a plane, consists of two semi-circular segments of radius $R_1 = 6\pi \, \mathrm{m}$ and $R_2 = 4\pi \, \mathrm{m}$. The magnitude of the resultant magnetic field at center O is $k \times 10^{-7} \, \mathrm{T}$. The value of $k$ is ______ (Given $\mu_0 = 4\pi \times 10^{-7} \, \mathrm{TmA^{-1}}$)

Answer: 1

Solution

Magnetic field due to AB & CD $= 0$ $$B_0 = |B_{R_1} - B_{R_2}|$$ $$= \frac{\mu_0 I}{4R_2} - \frac{\mu_0 I}{4R_1}$$ $$= \frac{4\pi \times 10^{-7} \times 12}{4} \left( \frac{1}{4\pi} - \frac{1}{6\pi} \right)$$ $$= 12\pi \times 10^{-7} \left( \frac{1}{12\pi} \right)$$ $$= 1 \times 10^{-7}$$ $$K = 1$$

Question 50

Physics · Current Electricity · Numerical

In the figure shown below, a resistance of $150.4\,\Omega$ is connected in series to an ammeter A of resistance $240\,\Omega$. A shunt resistance of $10\,\Omega$ is connected in parallel with the ammeter. The reading of the ammeter is _____ mA.

Answer: 5

Solution

The equivalent resistance is given by $R_{eq} = R_1 + R_2$. Calculating $R_{eq}$: $$R_{eq} = 150.4 + \frac{240 \times 10}{240 + 10}$$ Simplifying, $$R_{eq} = 150.4 + 9.6 = 160 \Omega$$ The current $I_1$ is given by $$I_1 = \frac{IR_2}{240}$$ Substituting the values, $$I_1 = \frac{20}{160} \times \frac{9.6}{2400} = \frac{1}{200} = 5 \times 10^{-3} \, A = 5 \, mA$$

Chemistry

Question 51

Chemistry · Structure of Atom · Single correct

Which of the following postulate of Bohr's model of hydrogen atom in not in agreement with quantum mechanical model of an atom?

  1. An atom in a stationary state does not emit electromagnetic radiation as long as it stays in the same state
  2. An atom can take only certain distinct energies $E_1, E_2, E_3$, etc. These allowed states of constant energy are called the stationary states of atom
  3. When an electron makes a transition from a higher energy stationary state to a lower energy stationary state, then it emits a photon of light
  4. The electron in a H atom's stationary state moves in a circle around the nucleus

Answer: (d)

Solution

The electron in a H-atom's stationary state moves in a spherical path.

Question 52

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

Given below are two statements Statement I : The N-N single bond is weaker and longer than that of P-P single bond Statement II : Compounds of group 15 elements in +3 oxidation states readily undergo disproportionation reactions. In the light of 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 false
  3. Statement I is false but statement II is true
  4. Both statement I and statement II are true

Answer: (b)

Solution

The $\mathrm{N} - \mathrm{N}$ single bond is weaker than $\mathrm{P} - \mathrm{P}$ due to more $\ell_p - \ell_p$ repulsion. Bond length implies $d_{p-p} > d_{N-N}$ (size increases, bond length increases). In group 15 elements, only N and P show disproportionation in the +3 oxidation state, while As, Sb, and Bi are almost inert for disproportionation in the +3 oxidation state. So both statements are false.

Question 53

Chemistry · Equilibrium · Single correct

Given below are two statements Statement I: A catalyst cannot alter the equilibrium constant $(K_c)$ of the reaction, temperature remaining constant Statement II: A homogenous catalyst can change the equilibrium composition of a system temperature remaining constant 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 is false
  4. Statement I is true but Statement II is false

Answer: (b)

Solution

A catalyst can change equilibrium composition if it is added at constant pressure, but it cannot change equilibrium constant.

Question 54

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

The metal ions that have the calculated spin only magnetic moment value of $4.9\,\mathrm{B.M.}$ are A. $\mathrm{Cr}^{2+}$ B. $\mathrm{Fe}^{2+}$ C. $\mathrm{Fe}^{3+}$ D. $\mathrm{Co}^{2+}$ E. $\mathrm{Mn}^{3+}$ Choose the correct answer from the options given below

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

Answer: (d)

Solution

Given magnetic moment = 4.9 B.M. We know M.M $=\sqrt{n(n+2)}$ B.M. Where, $n \rightarrow$ No. of unpaired $e^-$ $4.9=\sqrt{n(n+2)}$ We get $n=4$ (A) $_{24}\mathrm{Cr}^{2+}\Rightarrow[\mathrm{Ar}]\,3d^4$ (4 unpaired $e^-$) (B) $_{26}\mathrm{Fe}^{2+}\Rightarrow[\mathrm{Ar}]\,3d^6$ (4 unpaired $e^-$) $(C)$ $_{26}\mathrm{Fe}^{3+}\Rightarrow[\mathrm{Ar}]\,3d^5$ (5 unpaired $e^-$) (D) $_{27}\mathrm{Co}^{3+}\Rightarrow[\mathrm{Ar}]\,3d^6$ (3 unpaired $e^-$) (E) $_{25}\mathrm{Mn}^{3+}\Rightarrow[\mathrm{Ar}]\,3d^4$ (4 unpaired $e^-)$

Question 55

Chemistry · Chemical Kinetics and Nuclear Chemistry · Single correct

In a reaction $A + B \rightarrow C$, initial concentrations of $A$ and $B$ are related as $[A]_0 = 8[B]_0$. The half lives of $A$ and $B$ are 10 min and 40 min. respectively. If they start to disappear at the same time, both following first order kinetics, after how much time will the concentration of both the reactants be same?

  1. 60 min
  2. 80 min
  3. 20 min
  4. 40 min

Answer: (d)

Solution

Given: $[A]_0 = 8[B]_0$. $[t_{1/2}]_A = 10 \, min$. $[t_{1/2}]_B = 40 \, min$. First order kinetics. $t = ?$ $[A]_t = [B]_t$ $-k_A \times t = -k_B \times t$ $\Rightarrow [A]_0 e = [B]_0 e$ $\Rightarrow \frac{[A]_0}{[B]_0} = e^{(k_A - k_B)t}$ $\Rightarrow 8 = e^{(k_A - k_B) \times t}$ $\Rightarrow \ln 8 = (k_A - k_B) \times t$ $\Rightarrow \ln 8 = \ln 2 \left( \frac{1}{(t_{a2})_A} - \frac{1}{(t_{a2})_B} \right) \times t$

Question 56

Chemistry · Biomolecules · Single correct

Which of the following is the correct structure of L-fructose?

Answer: (c)

Solution

The structures shown are of D-Fructose and L-Fructose. The D-Fructose has the hydroxyl group on the right side, while the L-Fructose has the hydroxyl group on the left side.

Question 57

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

Identify the correct statements from the following Choose the correct answer from the options given below

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

Answer: (c)

Solution

In option C are homologues to each other and option D are only organic molecules not isomers.

Question 58

Chemistry · Some Basic Concepts of Chemistry · Single correct

Among $10^{-9} \, \mathrm{g}$ (each) of the following elements, which one will have the highest number of atoms? Element: Pb, Po, Pr and Pt

  1. Po
  2. Pr
  3. Pb
  4. Pt

Answer: (b)

Solution

No. of atoms = $\frac{Mass in g}{Molar Mass (g/mol)}$ $\times$ N_A. Therefore for the same mass, the element having the least molar mass will have the higher number of atoms. - M_{$\mathrm{Po}$} = 209 - M_{$\mathrm{Pr}$} = 141 - M_{$\mathrm{Pb}$} = 207 - M_{$\mathrm{Pt}$} = 195

Question 59

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

Which of the following statements are correct? A. The process of the addition an electron to a neutral gaseous atom is always exothermic B. The process of removing an electron from an isolated gaseous atom is always endothermic C. The $1^{st}$ ionization energy of the boron is less than that of the beryllium D. The electronegativity of C is 2.5 in $CH_4$ and $CCl_4$ E. Li is the most electropositive among elements of group I Choose the correct answer from the options gives below

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

Answer: (a)

Solution

The process of adding an $e^-$ to a neutral gaseous atom is not always exothermic; it may be exothermic or endothermic. Be B $$1s^22s^2 1s^22s^22p^1$$ In Be, the 2s subshell is fully filled. So, high energy is needed to remove $e^-$ as compared to B. In $\mathrm{CCl_4}$: $$\delta^- -Cl \delta^+ -C \delta^- -Cl$$ Due to partially positive charge $z_{eff} \uparrow$, EN $\uparrow$. So, EN of C $\Rightarrow \mathrm{CCl_4} > \mathrm{CH_4}$. Cs is most electropositive.

Question 60

Chemistry · Solutions · Single correct

Which of the following properties will change when system containing solution 1 will become solution 2?

  1. Molar heat capacity
  2. Density
  3. Concentration
  4. Gibbs free energy

Answer: (d)

Solution

Both solutions are having same composition, which is 1 mole of 'x' in 1 'l' water, so all the intensive properties will remain same, but as total amount is greater in solution '1' compared to solution '2'. So extensive properties will be different hence Gibbs free energy will be different.

Question 61

Chemistry · Aldehydes, Ketones and Carboxylic Acids · Single correct

Number of molecules from below which cannot give iodoform reaction is : Ethanol, Isopropyl alcohol, Bromoacetone, 2-Butanol, 2-Butanone, Butanal, 2-Pentanone, 3-Pentanone, Pentanal and 3-Pentanol

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

Answer: (b)

Solution

Q7. Following will not give iodoform reaction/test. (1) Butanal (2) 2-Pentanone (3) Pentanal (4) 3-Pentanol

Question 62

Chemistry · Amines · Single correct

Identify [A], [B], and [C], respectively in the following reaction sequence:

Answer: (c)

Solution

Question 63

Chemistry · Amines · Single correct

In the following reactions, which one is NOT correct?

Answer: (a)

Solution

The reaction of the compound with $\mathrm{N_2Cl}$ in the presence of $\mathrm{EtOH}$ does not yield the expected $\mathrm{OEt}$ product. Instead, a deamination reaction occurs, resulting in the formation of benzene.

Question 64

Chemistry · Co-ordination Compounds · Single correct

The correct order of the complexes $[\mathrm{Co(NH_3)_5(H_2O)}]^{3+}$ (A), $[\mathrm{Co(NH_3)_6}]^{3+}$ (B), $[\mathrm{Co(CN)_6}]^{3-} (C)$ and $[\mathrm{CoCl(NH_3)_5}]^{2+}$ (D) in terms wavelength of light absorbed is :

  1. D>A>B>C
  2. C>B>D>A
  3. D>C>B>A
  4. C>B>A>D

Answer: (a)

Solution

We know $E = h \nu = \frac{hC}{\lambda}$. $E \propto \frac{1}{\lambda}$ Here all Co in +3 oxidation state. So, as the ligand field strength increases, CFSE increases. Order of field strength of ligand: CN $>$ $\mathrm{NH_3}$ $>$ $\mathrm{H_2O}$ $>$ $\mathrm{Cl^-}$ CFSE order: C $>$ B $>$ A $>$ D Wavelength order: D $>$ A $>$ B $>$ C

Question 65

Chemistry · Equilibrium · Single correct

In the following system, $\mathrm{PCl}_5(\mathrm{g}) \rightleftharpoons \mathrm{PCl}_3(\mathrm{g}) + \mathrm{Cl}_2(\mathrm{g})$ at equilibrium, upon addition of xenon gas at constant T$\&$p, the concentration of

  1. $\mathrm{PCl}_5$ will increase
  2. $\mathrm{Cl}_2$ will decrease
  3. $\mathrm{PCl}_5, \mathrm{PCl}_3 \& \mathrm{Cl}_2$ remain constant
  4. $\mathrm{PCl}_3$ will increase

Answer: (b)

Solution

On addition of inert gas at constant $P$ and $T$, reaction moves in the direction of greater number of moles so it will shift in forward direction, so $[\mathrm{PCl}_5]$ decrease and $[\mathrm{PCl}_3]$ and $[\mathrm{Cl}_2]$ will increase.

Question 66

Chemistry · Solutions · Single correct

2 moles each of ethylene glycol and glucose are dissolved in 500 g of water. The boiling point of the resulting solution is : (Given : Ebullioscopic constant of water $= 0.52 K kg mol^{-1}$)

  1. 379.2 K
  2. 377.3 K
  3. 375.3 K
  4. 277.3 K

Answer: (b)

Solution

Given $\Delta T_b = i_1 \, m_1 k_b + i_2 \, m_2 k_b$. $$= 1 \times \frac{2}{0.5} \times 0.52 + \frac{1 \times 2}{0.5} \times 0.52 = 4.16$$ $$(T_b)_{solution} = 373.16 + 4.16 = 377.3 \, \mathrm{K}.$$

Question 67

Chemistry · Hydrocarbons · Single correct

Which compound would give 3-methyl-6oxoheptanal upon ozonolysis?

Answer: (b)

Solution

The reaction shown is ozonolysis of 1,3-dimethylcyclohexene. The ozonolysis process involves the cleavage of the double bond and formation of carbonyl compounds. The product formed is 3-Methyl-6-ketoheptanal.

Question 68

Chemistry · Co-ordination Compounds · Single correct

Match the LIST-I with LIST-II \begin{tabular}{|c|l|c|l|} \hline \multicolumn{2}{|c|}{LIST-I} & \multicolumn{2}{c|}{LIST-II} \\ \multicolumn{2}{|c|}{(Molecules/ion)} & \multicolumn{2}{c|}{(Hybridisation of central atom)} \\ \hline A. & PF$_5$ & I. & $dsp^2$ \\ \hline B. & SF$_6$ & II. & $sp^3d$ \\ \hline C. & Ni(CO)$_4$ & III. & $sp^3d^2$ \\ \hline D. & [PtCl$_4$]$^{2-}$ & IV. & $sp^3$ \\ \hline \end{tabular} 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-I, C-IV, D-II

Answer: (a)

Solution

For $PF_5$: $5\sigma + 0\ell p \rightarrow sp^3d$. For $SF_6$: $6\sigma + 0\ell p \rightarrow sp^3d^2$. For $Ni(CO)_4$: Ni is in the zero oxidation state. In the presence of a ligand field, Ni(0) has the electron configuration $[Ar]$ with $sp^3$ hybridisation. For $[PtCl_4]^{2-}$: Pt is in the $+2$ oxidation state. In the presence of a ligand field, $Pt^{2+}$ has the electron configuration $[Kr]$ with $dsp^2$ hybridisation.

Question 69

Chemistry · Aldehydes, Ketones and Carboxylic Acids · Single correct

The least acidic compound, among the following is:

  1. D
  2. A
  3. B
  4. C

Answer: (a)

Solution

C.B. of terminal alkyne will be sp hybridisation and localised. In other C.B. will be resonance stabilised.

Question 70

Chemistry · Electrochemistry · Single correct

Correct order of limiting molar conductivity for cations in water at 298 $\mathrm{K}$ is:

  1. $\mathrm{H}^+ > \mathrm{Na}^+ > \mathrm{K}^+ > \mathrm{Ca}^{2+} > \mathrm{Mg}^{2+}$
  2. $\mathrm{H}^+ > \mathrm{Ca}^{2+} > \mathrm{Mg}^{2+} > \mathrm{K}^+ > \mathrm{Na}^+$
  3. $\mathrm{Mg}^{2+} > \mathrm{H}^+ > \mathrm{Ca}^{2+} > \mathrm{K}^+ > \mathrm{Na}^+$
  4. $\mathrm{H}^+ > \mathrm{Na}^+ > \mathrm{Ca}^{2+} > \mathrm{Mg}^{2+} > \mathrm{K}^+$

Answer: (b)

Solution

Limiting Molar Conductivities of Ions: $\oplus H: 349.8 \, \mathrm{Scm^2 \, mol^{-1}}$ $Na^+: 50.11 \, \mathrm{Scm^2 \, mol^{-1}}$ $K^+: 73.52 \, \mathrm{Scm^2 \, mol^{-1}}$ $Ca^{+2}: 119 \, \mathrm{Scm^2 \, mol^{-1}}$ $Mg^{+2}: 106.12 \, \mathrm{Scm^2 \, mol^{-1}}$ Therefore correct order of limiting molar conductivity of cations will be - $\oplus H > Ca^{+2} > Mg^{+2} > K^+ > Na^+$

Question 71

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

During estimation of nitrogen by Dumas' method of compound X (0.42 $\mathrm{g}$): _____ $\mathrm{mL}$ of $\mathrm{N}_2$ gas will be liberated at STP. (nearest integer) (Given molar mass in $\mathrm{g/mol}^{-1}$ : $\mathrm{C}$ : 12, $\mathrm{H}$ : 1, $\mathrm{N}$ : 14)

Answer: 111

Solution

M.wt. of given compound = 86 Applying POAC on 'N' $n_X \times 2 = n_{N_2} \times 2$ $$\frac{0.42}{86} = n_{N_2}$$ Therefore, the volume of $N_2$ at STP is $$\frac{0.42}{86} \times 22.4 \, \mathrm{L}$$ $$= 0.1108 \, \mathrm{L} = 110.8 \, \mathrm{mL}$$

Question 72

Chemistry · Some Basic Concepts of Chemistry · Numerical

$0.5\,\mathrm{g}$ of an organic compound on combustion gave $1.46\,\mathrm{g}$ of $\mathrm{CO_2}$ and $0.9\,\mathrm{g}$ of $\mathrm{H_2O}$. The percentage of carbon in the compound is ________. (Nearest integer) [Given: Molar mass (in $\mathrm{g\,mol^{-1}}$) C: $12$, H: $1$, O: $16$]

Answer: 80

Solution

Applying POAC on 'C' (mole) of 'C' in compound = n_{$\mathrm{CO_2}$} $\times$ 1 So mass of 'C' in compound $$= \frac{1.46}{44} \times 12$$ So, $\%$ of 'C' in compound = $$\frac{1.46}{44} \times \frac{12}{0.5} \times 100$$ $$= 79.63$$

Question 73

Chemistry · Co-ordination Compounds · Numerical

The number of optical isomers exhibited by the iron complex (A) obtained from the following reaction is ___ $\mathrm{FeCl_3 + KOH + H_2C_2O_4 \rightarrow A}$

Answer: 2

Solution

Given the reaction $\mathrm{FeCl_3} + \mathrm{KOH} + \mathrm{H_2SO_4} \rightarrow \mathrm{K_3[Fe(C_2O_4)_3]}$. The complex $[\mathrm{Fe(C_2O_4)_3}]^{3-}$ is of the $\mathrm{[M(AA)_3]}$ type. So the total optical isomers are $2$.

Question 74

Chemistry · Thermodynamics · Numerical

Given : $$\Delta H^\Theta_{sub} \left[ C( graphite ) \right] = 710 \, kJ mol^{-1}$$ $$\Delta_{C-H}H^\Theta = 414 \, kJ mol^{-1}$$ $$\Delta_{H-H}H^\Theta = 436 \, kJ mol^{-1}$$ $$\Delta_{C=C}H^\Theta = 611 \, kJ mol^{-1}$$ The $$\Delta H^\Theta_{f}$$ for $$CH_2 = CH_2$$ is _____ $$kJ mol^{-1}$$ (nearest integer value)

Answer: 25

Solution

The reaction is given as follows: $$2\mathrm{C}_{(s)} + 2\mathrm{H}_2{(g)} \rightarrow \mathrm{CH}_2 = \mathrm{CH}_2{(g)} : [\Delta H_f^\circ]_{\mathrm{C}_2\mathrm{H}_4{(g)}}$$ The enthalpy change is calculated as: $$[\Delta H_f^\circ]_{\mathrm{C}_2\mathrm{H}_4{(g)}} = 2 \times [\Delta H_{sub}^\circ]_{\mathrm{C}_{(s)}} + 2 \times \Delta H_{H--H}^\circ - 1 \times \Delta H_{C=C}^\circ - 4 \times \Delta H_{CH}^\circ$$ Substituting the values: $$\Rightarrow [\Delta H_f^\circ]_{\mathrm{C}_2\mathrm{H}_4{(g)}} = (2 \times 710) + (2 \times 436) - 611 - 4 \times 414$$ Simplifying gives: $$\Rightarrow [\Delta H_f^\circ]_{\mathrm{C}_2\mathrm{H}_4{(g)}} = 25 \, \mathrm{kJ/mol}$$

Question 75

Chemistry · The p-Block Elements (Group 15, 16, 17 & 18) · Fill in the blank

Consider the following reactions: $A+\overset{\text{Little amount}}{\mathrm{NaCl}}+\mathrm{H_2SO_4}\rightarrow\mathrm{CrO_2Cl_2}+\text{Side Products}$ $\mathrm{CrO_2Cl_2}\,(\text{vapour})+\mathrm{NaOH}\rightarrow B+\mathrm{NaCl}+\mathrm{H_2O}$ $B+\mathrm{H^+}\rightarrow C+\mathrm{H_2O}$ The number of terminal 'O' present in the compound 'C' is ______.

Answer: 6

Solution

$Cr_2O_7^{2-}+NaCl+H_2SO_4\rightarrow CrO_2Cl_2$ $CrO_2Cl_2\ \text{(Vapour)}+NaOH\rightarrow Na_2CrO_4+NaCl+H_2O$ $\mathrm{Na_2Cr_2O_7 \rightarrow 2Na^+ + Cr_2O_7^{2-}}$ No. of terminal "O" = 6