JEE Main 26 June 2022 Shift 1 question paper with solutions

JEE Main 26 June 2022 Shift 1: 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 · Relations and Functions · Single correct

Let $f(x) = \frac{x-1}{x+1}$, $x \in \mathbb{R} - \{0, -1, 1\}$. If $f^{n+1}(x) = f(f^n(x))$ for all $n \in \mathbb{N}$, then $f^6(6) + f^7(7)$ is equal to:

  1. $\frac{7}{6}$
  2. $-\frac{3}{2}$
  3. $\frac{7}{12}$
  4. $-\frac{11}{12}$

Answer: (b)

Solution

Given $f(x) = \frac{x-1}{x+1}$. Therefore, $f^2(x) = f(f(x)) = \frac{x-1}{x+1} \cdot \frac{-1}{x-1} = \frac{-1}{x}$. Then, $f^3(x) = f(f^2(x)) = f\left(\frac{-1}{x}\right) = \frac{x+1}{1-x}$. Thus, $f^4(x) = f\left(\frac{x+1}{1-x}\right) = \frac{-1}{x}$. Therefore, $f^6(x) = \frac{-1}{x} \Rightarrow f^6(6) = \frac{-1}{8}$. Next, $f^7(x) = \left(\frac{-1}{x}\right) = \frac{x+1}{1-x}$. Thus, $f^7(7) = \frac{8}{-6} = \frac{-4}{3}$. Therefore, $\frac{1}{6} + \frac{4}{3} = \frac{3}{2}$.

Question 2

Maths · Complex Numbers and Quadratic Equations · Single correct

Let $A = \left\{ z \in \mathbb{C} : \left| \frac{z+1}{z-1} \right| < 1 \right\}$ and $B = \left\{ z \in \mathbb{C} : \arg \left( \frac{z-1}{z+1} \right) = \frac{2\pi}{3} \right\}$. Then $A \cap B$ is:

  1. a portion of a circle centred at $\left( 0, -\frac{1}{\sqrt{3}} \right)$ that lies in the second and third quadrants only
  2. a portion of a circle centred at $\left( 0, -\frac{1}{\sqrt{3}} \right)$ that lies in the second quadrant only
  3. an empty set
  4. a portion of a circle of radius $\frac{2}{\sqrt{3}}$ that lies in the third quadrant only

Answer: (b)

Solution

Set A implies $\($ $\left$| $\frac{z+1}{z-1}$ $\right$| < 1 $\)$ which implies $\($ |z+1| < |z-1| $\)$. This leads to $\($ (x+1)^2 + y^2 < (x-1)^2 + y^2 $\)$ which implies $\($ x < 0 $\)$. Set B implies $\($ $\arg$ $\left$( $\frac{z-1}{z+1}$ $\right$) = $\frac{2\pi}{3}$ $\)$. This leads to $\($ $\tan$^{-1} $\left$( $\frac{y}{x-1}$ $\right$) - $\tan$^{-1} $\left$( $\frac{y}{x+1}$ $\right$) = $\frac{2\pi}{3}$ $\)$. This results in $\($ x^2 + y^2 + $\frac{2y}{\sqrt{3}}$ - 1 = 0 $\)$. The intersection $\($ A $\cap$ B $\)$ implies the center is $\($ $\left$( 0, -$\frac{1}{\sqrt{3}}$ $\right$) $\)$.

Question 3

Maths · Matrices · Single correct

Let A be a 3 $\times$ 3 invertible matrix. If $|adj \, (24A)| = adj(3adj(2A))|$, then $|A|^2$ is equal to:

  1. 6^6
  2. 2^{12}
  3. 2^6
  4. 1

Answer: (c)

Solution

Given $adj(24A)=adj(3(adj(2A)))$ $\Rightarrow |24A|^2=(3\,adj(2A))^2$ $\Rightarrow (24^3|A|)^2=(3^3|adj(2A)|)^2$ $=3^6(|2A|^2)^2$ $\Rightarrow 24^6|A|^2=3^6\times2^{12}|A|^4$ $\Rightarrow |A|^2=\frac{24^6}{3^6\times2^{12}}$ $=64$

Question 4

Maths · Determinants · Single correct

The ordered pair (a, b), for which the system of linear equations 3x - 2y + z = b 5x - 8y + 9z = 3 2x + y + az = -1 has no solution, is :

  1. (3, $\frac{1}{3}$)
  2. (-3, $\frac{1}{3}$)
  3. (-3, -$\frac{1}{3}$)
  4. (3, -$\frac{1}{3}$)

Answer: (c)

Solution

Given the determinant: $$\begin{vmatrix} 3 & -2 & 1 \\ 5 & -8 & 9 \\ 2 & 1 & a \end{vmatrix} = 0$$ Expanding, we have: $$3(-8a - 9) + 2(5a - 18) + 1(21) = 0$$ This implies $a = -3$. Also, consider $$\Delta_2 = \begin{vmatrix} 3 & -2 & b \\ 5 & 8 & 3 \\ 2 & 1 & -1 \end{vmatrix}$$ If $b = \frac{1}{3}$, then $\Delta_2 = 0$. So $b$ must be equal to $$-\frac{1}{3}$$

Question 5

Maths · Binomial Theorem · Single correct

The remainder when $(2021)^{2023}$ is divided by 7 is :

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

Answer: (c)

Solution

Given $ (2021)^{2023} = (7\lambda - 2)^{2023} $. $$ = \binom{2023}{0} (7A)^{2023} - \ldots - \binom{2023}{2023} 2^{2023} $$ $$ = 7t - 2^{2023} $$ Therefore, $ -2^{2023} = -2 \times 2^{2022} $. $$ = -2 \times (2^3)^{674} $$ $$ = -2 (1 + 7\mu)^{674} $$ $$ = -(7\alpha + 2) $$ Thus, the remainder is $ -2 $ or $ +5 $.

Question 6

Maths · Limits and Derivatives · Single correct

$\lim$_{x $\to$ $\frac{1}{\sqrt{2}}$} $\frac{\sin(\cos^{-1} x) - x}{1 - \tan(\cos^{-1} x)}$ is equal to:

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

Answer: (d)

Solution

Evaluate the limit: $$\lim_{x \to \frac{1}{\sqrt{2}}} \frac{\sin(\cos^{-1} x) - x}{1 - \tan(\cos^{-1} x)}$$ Substitute the trigonometric identities: $$\lim_{x \to \frac{1}{\sqrt{2}}} \frac{\sin\left(\sin^{-1}\sqrt{1-x^2}\right) - x}{1 - \tan\left(\tan^{-1}\left(\frac{\sqrt{1-x^2}}{x}\right)\right)}$$ Simplify the expression: $$\lim_{x \to \frac{1}{\sqrt{2}}} \frac{\sqrt{1-x^2} - x}{1 - \frac{\sqrt{1-x^2}}{x}}$$ Evaluate the limit: $$\lim_{x \to \frac{1}{\sqrt{2}}} (-x) = -\frac{1}{\sqrt{2}}$$

Question 7

Maths · Continuity and Differentiability · Single correct

Let $f, g : \mathbb{R} \to \mathbb{R}$ be two real valued functions defined as $f(x) = \begin{cases} -|x+3|, & x < 0 \\ e^x, & x \geq 0 \end{cases}$ and $g(x) = \begin{cases} x^2 + k_1 x, & x < 0 \\ 4x + k_2, & x \geq 0 \end{cases}$, where $k_1$ and $k_2$ are real constants. If (gof) is differentiable at $x = 0$, then (gof)(-4) + (gof)(4) is equal to:

  1. 4(e^4 + 1)
  2. 2(2e^4 + 1)
  3. 4e^4
  4. 2(2e^4 - 1)

Answer: (d)

Solution

Given $$f(x) = \begin{cases} x+3 & ; \ x 0 \end{cases}$$ Check continuity at $x = 0$ $$gof(0) = g\left(f(0^-)\right) = g\left(f(0^+)\right)$$ $$4 + k_2 = 9 - 3k_1 = 4 + k_2$$ $$3k_1 + k_2 = 5 \ldots (a)$$ Differentiate $$\left(g(f(x))\right)' = \begin{cases} 2(x+3) + k_1 & ; \ x < -3 \\ 2(x+3) - k_1 & ; \ -3 \leq x < 0 \\ 4e^x & ; \ x \geq 0 \end{cases}$$ $$6 - k_1 = 4$$ $$k_1 = 2 \ldots (b)$$ Therefore, $k_1 = 2, k_2 = -1$ $$gof(x) = \begin{cases} (x+3)^2 + 2(x+3) & ; \ x < -3 \\ (x+3)^2 - 2(x+3) & ; \ -3 \leq x < 0 \\ 4e^x - 1 & ; \ x \geq 0 \end{cases}$$ $$gof(-4) + gof(4) = 4e^4 - 2$$ $$\Rightarrow 2\left(2e^4 - 1\right)$$

Question 8

Maths · Applications of Derivatives · Single correct

The sum of the absolute minimum and the absolute maximum values of the function $f(x) = |3x - x^2 + 2| - x$ in the interval $[-1, 2]$ is :

  1. $\frac{\sqrt{17} + 3}{2}$
  2. $\frac{\sqrt{17} + 5}{2}$
  3. 5
  4. $\frac{9 - \sqrt{17}}{2}$

Answer: (a)

Solution

Given $$f(x) = \begin{cases} x^2 - 4x - 2, & \forall x \in \left(-1, \frac{3 - \sqrt{17}}{2}\right) \\ -x^2 + 2x + 2, & \forall x \in \left(\frac{3 - \sqrt{17}}{2}, 2\right) \end{cases}$$ $f'(x)$ when $x \in \left(-1, \frac{3 - \sqrt{17}}{2}\right)$ $$f'(x) = 2x - 4 = 0 \implies x = 2$$ $$f'(x) = 2(x - 2) \implies f'(x) is always \downarrow$$ $$f(2) = 2$$ $$f(-1) = 3$$ $$f\left(\frac{3 - \sqrt{17}}{2}\right) = \frac{\sqrt{17} - 3}{2}$$ $f'(x)$ when $x \in \left(\frac{3 - \sqrt{17}}{2}, 2\right)$ $$f'(x) = -2x + 2$$ $$f'(x) = -2(x - 1)$$ $$f'(x) = 0 when x = 1$$ $$f(1) = 3$$ absolute minimum value $= \frac{\sqrt{17} - 3}{2}$ absolute maximum value $= 3$ Sum $= \frac{\sqrt{17} - 3}{2} + 3 = \frac{\sqrt{17} + 3}{2}$

Question 9

Maths · Applications of Derivatives · Single correct

Let S be the set of all the natural numbers, for which the line $\frac{x}{a} + \frac{y}{b} = 2$ is a tangent to the curve $$\left( \frac{x}{a} \right)^n + \left( \frac{y}{b} \right)^n = 2$$ at the point $(a, b)$, $ab \neq 0$. Then:

  1. S = $\phi$
  2. n(S) = 1
  3. S = {$2k : k$ $\in$ $\mathbb{N}$\}
  4. S = $\mathbb{N}$

Answer: (d)

Solution

Given $\($ $\left$( $\frac{x}{a}$ $\right$)^n + $\left$( $\frac{y}{b}$ $\right$)^n = 2 $\)$. Slope of tangent at $\($(a, b)$\)$ is calculated as follows: $\[$ n $\left$( $\frac{x}{a}$ $\right$)^{n-1} $\cdot$ $\frac{1}{a}$ + n $\left$( $\frac{y}{b}$ $\right$)^{n-1} $\cdot$ $\frac{1}{b}$ $\frac{dy}{dx}$ = 0 $\]$ $\[$ $\left$. $\frac{dy}{dx}$ $\right$|_{(a,b)} = -$\frac{b}{a}$ $\]$ Therefore, the equation of the tangent is: $\[$ y - b = -$\frac{b}{a}$ (x - a) $\]$ $\[$ $\frac{x}{a}$ + $\frac{y}{b}$ = 2 $\forall$ $\ $n $\in$ $\mathbb{N}$ $\]$

Question 10

Maths · Applications of Integrals · Single correct

The area bounded by the curve $y = |x^2 - 9|$ and the line $y = 3$ is :

  1. 4(2$\\sqrt{3}$ + $\\sqrt{6}$ - 4)
  2. 4(4$\\sqrt{3}$ + $\\sqrt{6}$ - 4)
  3. 8(4$\\sqrt{3}$ + 3$\\sqrt{6}$ - 9)
  4. 8(4$\\sqrt{3}$ + $\\sqrt{6}$ - 9)

Answer: (d)

Solution

Area of shaded region $$= 2 \int_{0}^{3} \left( \sqrt{9+y} - \sqrt{9-y} \right) \, dy + 2 \int_{3}^{9} \left( \sqrt{9-y} \right) \, dy$$ $$= 2 \left[ \int_{0}^{3} (9+y)^{1/2} \, dy - \int_{0}^{3} (9-y)^{1/2} \, dy + \int_{3}^{9} (9-y)^{1/2} \, dy \right]$$ $$= 2 \left[ \frac{2}{3} (9+y)^{3/2} \bigg|_{0}^{3} + \frac{2}{3} (9-y)^{3/2} \bigg|_{3}^{9} - \frac{2}{3} (9-y)^{3/2} \bigg|_{0}^{3} \right]$$ $$= \frac{4}{3} \left[ 12\sqrt{12} - 27 + 6\sqrt{6} - 27 - (0 - 6\sqrt{6}) \right]$$ $$= \frac{4}{3} \left[ 24\sqrt{3} + 12\sqrt{6} - 54 \right]$$ $$= 8 \left( 4\sqrt{3} + 2\sqrt{6} - 9 \right)$$

Question 11

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

Let R be the point (3, 7) and let P and Q be two points on the line x + y = 5 such that PQR is an equilateral triangle. Then the area of $\triangle$ PQR is :

  1. $\frac{25}{4\sqrt{3}}$
  2. $\frac{25\sqrt{3}}{2}$
  3. $\frac{25}{\sqrt{3}}$
  4. $\frac{25}{2\sqrt{3}}$

Answer: (d)

Solution

Given $x + y = 5$ and $\frac{5}{\sqrt{2}}$. We have $\sin 60^\circ = \frac{\frac{5}{\sqrt{2}}}{a}$. Solving for $a$, we get $a = \frac{5\sqrt{2}}{3}$. The area of $\triangle PQR$ is $\frac{\sqrt{3}}{4} a^2 = \frac{25}{2\sqrt{3}}$.

Question 12

Maths · Conic Sections · Single correct

Let C be a circle passing through the points A(2, -1) and B(3, 4). The line segment AB is not a diameter of C. If r is the radius of C and its centre lies on the circle $(x - 5)^2 + (y - 1)^2 = \frac{13}{2}$, then $r^2$ is equal to:

  1. 32
  2. $\frac{65}{2}$
  3. $\frac{61}{2}$
  4. 30

Answer: (b)

Solution

AB = $\sqrt{26}$. The equation for the radius squared is given by $r^2 = CM^2 + AM^2$. Substituting the values, we have: $$r^2 = \left(2 \times \frac{\sqrt{13}}{2}\right)^2 + \left(\frac{\sqrt{13}}{2}\right)^2$$ Simplifying, we find: $$r^2 = \frac{65}{2}$$

Question 13

Maths · Conic Sections · Single correct

Let the normal at the point P on the parabola $y^2 = 6x$ pass through the point $(5, -8)$. If the tangent at P to the parabola intersects its directrix at the point Q, then the ordinate of the point Q is:

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

Answer: (b)

Solution

Equation of normal: $y = -tx + 2at + at^3$ $\($ $\left$( a = $\frac{3}{2}$ $\right$) $\)$ since passing through $(5, -8)$, we get $t = -2$. Co-ordinate of $Q$: $(6, -6)$. Equation of tangent at $Q$: $x + 2y + 6 = 0$. Put $x = -\frac{3}{2}$ to get $R \left( -\frac{3}{2}, -\frac{9}{4} \right)$.

Question 14

Maths · Three Dimensional Geometry · Single correct

If the two lines $l_1: \frac{x-2}{3} = \frac{y+1}{-2}$, $z = 2$ and $l_2: \frac{x-1}{1} = \frac{2y+3}{\alpha} = \frac{z+5}{2}$ are perpendicular, then an angle between the lines $l_2$ and $l_3: \frac{1-x}{3} = \frac{2y-1}{-4} = \frac{z}{4}$ is:

  1. $\cos^{-1}\left(\frac{29}{4}\right)$
  2. $\sec^{-1}\left(\frac{29}{4}\right)$
  3. $\cos^{-1}\left(\frac{2}{29}\right)$
  4. $\cos^{-1}\left(\frac{2}{\sqrt{29}}\right)$

Answer: (b)

Solution

For $l_1$: $\($ $\frac{x-2}{3}$ = $\frac{y+1}{-2}$ = $\frac{z-2}{0}$ $\)$ For $l_2$: $\($ $\frac{x-1}{1}$ = $\frac{y+3/2}{\alpha/2}$ = $\frac{z+5}{2}$ $\)$ For $l_3$: $\($ $\frac{x-1}{-3}$ = $\frac{y-1/2}{-2}$ = $\frac{z-0}{4}$ $\)$ $l_1 \perp l_2 \Rightarrow \frac{|3-\alpha+0|}{\sqrt{13} \sqrt{1+\frac{\alpha^2}{4}+4}} = 0 \Rightarrow \alpha = 3$ Angle between $l_2$ and $l_3$: $$\cos \theta = \frac{|1 \times (-3) + (-2)(\alpha/2) + 2 \times 4|}{\sqrt{1+4+\frac{\alpha^2}{4}} \sqrt{9+16+4}}$$ $$\cos \theta = \frac{|-3-\alpha+8|}{\sqrt{5+\frac{\alpha^2}{4}} \sqrt{29}}$$ Put $\alpha = 3$ $$\cos \theta = \frac{2}{\sqrt{\frac{29}{4}}} = \frac{4}{29}$$ $$\theta = \cos^{-1} \left( \frac{4}{29} \right) \Rightarrow \theta = \sec^{-1} \left( \frac{29}{4} \right)$$

Question 15

Maths · Three Dimensional Geometry · Single correct

Let the plane $2x + 3y + z + 20 = 0$ be rotated through a right angle about its line of intersection with the plane $x - 3y + 5z = 8$. If the mirror image of the point $\left(2, -\frac{1}{2}, 2\right)$ in the rotated plane is $B(a, b, c)$, then:

  1. $\frac{a}{8} = \frac{b}{5} = \frac{c}{-4}$
  2. $\frac{a}{4} = \frac{b}{5} = \frac{c}{-2}$
  3. $\frac{a}{8} = \frac{b}{-5} = \frac{c}{4}$
  4. $\frac{a}{4} = \frac{b}{5} = \frac{c}{2}$

Answer: (a)

Solution

Let equation of rotated plane be: $$(2x + 3y + z + 20) + \lambda (x - 3y + 5z - 8) = 0$$ $$(2 + \lambda)x + (3 - 3\lambda)y + (1 + 5\lambda)z + 20 - 8\lambda = 0$$ Above plane is perpendicular to $2x + 3y + z + 20 = 0$. So, $(2 + \lambda) \cdot 2 + (3 - 3\lambda) \cdot 3 + (1 + 5\lambda) \cdot 1 = 0 \Rightarrow \lambda = 7$. Therefore, equation of rotated plane is: $$x - 2y + 4z - 4 = 0$$ Mirror image of $A \left(2, \frac{-1}{2}, 2\right)$ in rotated plane is $B(a, b, c)$. Equation of $AB$: $$\frac{x - 2}{1} = \frac{y + 1/2}{-2} = \frac{z - 2}{4} = k$$ Let coordinate of $B$ be $(2 + k, \frac{-1}{2} - 2k, 2 + 4k)$. Midpoint of $AB$ is: $$\left(2 + \frac{k}{2}, \frac{-1}{2} - k, 2 + 2k\right)$$ which will lie on the plane $x - 2y + 4z - 4 = 0$. Hence $k = \frac{-2}{3}$. Therefore $B$ is: $$\left(\frac{4}{3}, \frac{5}{6}, \frac{-2}{3}\right) \equiv \left(\frac{8}{6}, \frac{5}{6}, \frac{-4}{6}\right)$$ So, $\frac{a}{8} = \frac{b}{5} = \frac{c}{-4}$.

Question 16

Maths · Vector Algebra · Single correct

If $\vec{a} \cdot \vec{b} = 1$, $\vec{b} \cdot \vec{c} = 2$ and $\vec{c} \cdot \vec{a} = 3$, then the value of $$\begin{vmatrix} \vec{a} \times (\vec{b} \times \vec{c}), \vec{b} \times (\vec{c} \times \vec{a}), \vec{c} \times (\vec{b} \times \vec{a}) \end{vmatrix}$$ is:

  1. 0
  2. -6 $\vec{a}$ $\cdot$ ($\vec{b}$ $\times$ $\vec{c}$)
  3. 12 $\vec{c}$ $\cdot$ ($\vec{a}$ $\times$ $\vec{b}$)
  4. -12 $\vec{b}$ $\cdot$ ($\vec{c}$ $\times$ $\vec{a}$)

Answer: (a)

Solution

Given $\vec{a} \times (\vec{b} \times \vec{c}) = (\vec{a} \cdot \vec{c}) \vec{b} - (\vec{a} \cdot \vec{b}) \vec{c} = 3 \vec{b} - \vec{c}$. $\vec{b} \times (\vec{c} \times \vec{a}) = (\vec{b} \cdot \vec{a}) \vec{c} - (\vec{b} \cdot \vec{c}) \vec{a} = \vec{c} - 2 \vec{a}$. $\vec{c} \times (\vec{b} \times \vec{a}) = (\vec{c} \cdot \vec{a}) \vec{b} - (\vec{c} \cdot \vec{b}) \vec{a} = 3 \vec{b} - 2 \vec{a}$. $[3 \vec{b} - \vec{c}, \vec{c} - 2 \vec{a}, 3 \vec{b} - 2 \vec{a}]$. $(3 \vec{b} - \vec{c}) \cdot [(\vec{c} - 2 \vec{a}) \times (3 \vec{b} - 2 \vec{a})]$. $(3 \vec{b} - \vec{c}) \cdot [3 (\vec{c} \times \vec{b}) - 2 (\vec{c} \times \vec{a}) - 6 (\vec{a} \times \vec{b})]$. $-6 [\vec{b} \ \vec{c} \ \vec{a}] + 6 [\vec{c} \ \vec{a} \ \vec{b}]$

Question 17

Maths · Probability · Single correct

Let a biased coin be tossed 5 times. If the probability of getting 4 heads is equal to the probability of getting 5 heads, then the probability of getting atmost two heads is:

  1. $\frac{275}{6^5}$
  2. $\frac{36}{5^4}$
  3. $\frac{181}{5^5}$
  4. $\frac{46}{6^4}$

Answer: (d)

Solution

Given $\mathrm{P(H)} = x$, $\mathrm{P(T)} = 1 - x$. $\mathrm{P(4H, 1T)} = \mathrm{P(5H)}$ $$\binom{5}{1} x^4 (1-x)^1 = \binom{5}{5} x^5$$ $$5(1-x) = x$$ $$6x = 5 = 0 x = \frac{5}{6}$$ $\mathrm{P(atmost\ 2H)}$ $= \mathrm{P(0H, 5T)} + \mathrm{P(1H, 4T)} + \mathrm{P(2H, 3T)}$ $$= \binom{5}{0} \left(\frac{1}{6}\right)^5 + \binom{5}{1} \cdot \frac{5}{6} \cdot \left(\frac{1}{6}\right)^4 + \binom{5}{2} \left(\frac{5}{6}\right)^3 \left(\frac{1}{6}\right)^3$$ $$= \frac{1}{6^5} (1 + 25 + 250) = \frac{276}{6^5}$$ $$= \frac{46}{6^4}$$

Question 18

Maths · Statistics · Single correct

The mean of the numbers a, b, 8, 5, 10 is 6 and their variance is 6.8. If M is the mean deviation of the numbers about the mean, then 25 M is equal to:

  1. 60
  2. 55
  3. 50
  4. 45

Answer: (a)

Solution

Given $$\sigma^2 = \frac{\sum_{i=1}^{5} (x_i - \bar{x})^2}{n}$$ Mean = 6 $$\frac{a + b + 8 + 5 + 10}{5} = 6$$ $$a + b = 7$$ $$b = 7 - a$$ $$6.8 = \frac{(a-6)^2 + (b-6)^2 + (8-6)^2 + (5-6)^2 + (10-6)^2}{5}$$ $$34 = (a-6)^2 + (7-a-6)^2 + 4 + 1 + 18$$ $$a^2 - 7a + 12 = 0 \Rightarrow a = 4 or a = 3$$ $$a = 4 a = 3$$ $$b = 3 b = 4$$ $$M = \frac{\sum_{i=1}^{5} |x_i - \bar{x}|}{n}$$ $$M = \frac{|a-6| + |b-6| + |8-6| + |5-6| + |10-6|}{5}$$ When $$a = 3, b = 4$$ $$M = \frac{3 + 2 + 2 + 1 + 4}{5}$$ When $$a = 4, b = 3$$ $$M = \frac{2 + 3 + 2 + 1 + 7}{5}$$ $$M = \frac{12}{5}$$ $$M = \frac{12}{5}$$ $$25M = 25 \times \frac{12}{5} = 60$$

Question 20

Maths · Mathematical Reasoning · Single correct

Let $\Delta, \nabla \in \{\land, \lor\}$ be such that $p \nabla q \Rightarrow ((p \nabla q) \nabla r)$ is a tautology. Then $(p \nabla q) \Delta r$ is logically equivalent to:

  1. $(p \Delta r) \lor q$
  2. $(p \Delta r) \land q$
  3. $(p \land r) \Delta q$
  4. $(p \nabla r) \land q$

Answer: (a)

Solution

Case-I If $\Delta \equiv \nabla \equiv \wedge$ then $\left( p \land q \right) \to \left( \left( p \land q \right) \land r \right)$ it can be false if $r$ is false, so not a tautology. Case-II If $\Delta \equiv \nabla \equiv \lor$ then $\left( p \lor q \right) \to \left( \left( p \lor q \right) \lor r \right) \equiv$ tautology then $\left( p \lor q \right) \lor r \equiv \left( p \Delta r \right) \lor q$. Case-III if $\Delta = \lor$, $\nabla = \land$ then $\left( p \land q \right) \to \left\{ \left( p \lor q \right) \land r \right\}$ Not a tautology (Check $p \to T$, $q \to T$, $r \to F$). Case-IV if $\Delta = \land$, $\nabla = \lor$ then $\left( p \land q \right) \to \left\{ \left( p \land q \right) \lor r \right\}$ Not a tautology.

Question 21

Maths · Complex Numbers and Quadratic Equations · Fill in the blank

The sum of the cubes of all the roots of the equation $x^4 - 3x^3 - 2x^2 + 3x + 1 = 10$ is .

Answer: 36

Solution

Given the equation $x^4 - 3x^3 - 2x^2 + 3x + 1 = 10$. Since $x = 0$ is not the root of this equation, divide it by $x^2$. $$x^2 - 3x - 2 + \frac{3}{x} + \frac{1}{x^2} = 0$$ Rewriting, we have: $$x^2 + \frac{1}{x^2} - 2 + 2 - 3 \left( x - \frac{1}{x} \right) - 2 = 0$$ Simplifying further: $$\left( x - \frac{1}{x} \right)^2 - 3 \left( x - \frac{1}{x} \right) = 0$$ Solving for $x$: $$x - \frac{1}{x} = 0, x - \frac{1}{x} = 3$$ For $x - \frac{1}{x} = 0$: $$x^2 - 1 = 0$$ Thus, $x = \pm 1$. For $x - \frac{1}{x} = 3$: $$x^2 - 3x - 1 = 0$$ Let $\alpha = 1$, $\beta = -1$, $\gamma + \delta = 3$, $\gamma \delta = -1$. Calculating $\alpha^3 + \beta^3 + \gamma^3 + \delta^3$: $$1 - 1 + (\gamma + \delta)((\gamma + \delta)^2 - 3\gamma \delta)$$ $$0 + 3(9 - 3(-1))$$ $$+ 3(12) = 36$$

Question 22

Maths · Permutations and Combinations · Numerical

There are ten boys $B_1, B_2, \ldots, B_{10}$ and five girls $G_1, G_2, \ldots, G_5$ in a class. Then the number of ways of forming a group consisting of three boys and three girls, if both $B_1$ and $B_2$ together should not be the members of a group, is

Answer: 1120

Solution

Given $n(B) = 10$ and $n(a) = 5$. The number of ways of forming a group of 3 girls and 3 boys is given by: $$\binom{10}{3} \times \binom{5}{3}$$ Calculating this, we have: $$= \frac{10 \times 9 \times 8}{3 \times 2} \times \frac{5 \times 4}{2} = 1200$$ The number of ways when two particular boys $B_1$ and $B_2$ are members of the group together is: $$\binom{8}{1} \times \binom{5}{3} = 8 \times 10 = 80$$ The number of ways when boys $B_1$ and $B_2$ are in the same group together is: $$= 1200 \times 80 = 1120$$

Question 23

Maths · Conic Sections · Fill in the blank

Let the common tangents to the curves $4(x^2 + y^2) = 9$ and $y^2 = 4x$ intersect at the point $Q$. Let an ellipse, centered at the origin $O$, has lengths of semi-minor and semi-major axes equal to $OQ$ and $6$, respectively. If $e$ and $l$ respectively denote the eccentricity and the length of the latus rectum of this ellipse, then $\frac{l}{e^2}$ is equal to __________.

Answer: d

Solution

Given $x^2 + y^2 = \frac{9}{4}$ and $y = 4x$. The equation of the line is $y = mx + \frac{1}{m}$. Compare equations (1) and (2): $$\pm \frac{3}{2} \sqrt{(1 + m^2)} = \frac{1}{m^2}$$ $$9m^2(1 + m^2) = 4$$ $$9m^4 + 9m^2 - 4 = 0$$ $$9m^4 + 12m^2 - 3m^2 - 4 = 0$$ $$3m^2(3m^2 + 4) - (3m^2 + 4) = 0$$ $$m^2 = -\frac{4}{3} (Rejected)$$ $$m^2 = \frac{1}{3} \implies m = \pm \frac{1}{\sqrt{3}}$$ Equation of common tangent: $$y = \frac{1}{\sqrt{3}} x + \sqrt{3}$$ On the X-axis, $y = 0$. $OQ = -3$ $b = |OQ| = 3$ $a = 6$ $$b^2 = a^2(1 - e^2) \implies e^2 = 1 - \frac{9}{36} = \frac{3}{4}$$ $$e = \frac{2b^2}{a} = \frac{2 \times 9}{6} = 3$$ $$\frac{e}{e^2} = \frac{3}{3/4} = 4$$

Question 24

Maths · Applications of Integrals · Numerical

Let $f(x) = \max\{|x + 1|, |x + 2|, \ldots, |x + 5|\}$. Then $$\int_{-6}^{0} f(x) \, dx$$ is equal to ________.

Answer: 21

Solution

Given $f(x) = \max\{|x+1|, |x+2|, |x+3|, |x+4|, |x+5|\}$. The integral is evaluated as follows: $$\int_{-6}^{0} f(x) \, dx = \int_{-6}^{-3} |x+1| \, dx + \int_{-3}^{0} |x+5| \, dx$$ This simplifies to: $$= -\int_{-6}^{-3} (x+1) \, dx + \int_{-3}^{0} (x+5) \, dx$$ Evaluating the integrals: $$= -\left[ \frac{x^2}{2} + x \right]_{-6}^{-3} + \left[ \frac{x^2}{2} + 5x \right]_{-3}^{0}$$ Substituting the limits: $$= -\left( \frac{9}{2} - 3 \right) - (18 - 6) + \left( 0 - \left( \frac{9}{2} - 15 \right) \right)$$ Simplifying further: $$= -\left[ \frac{3}{2} - 12 \right] + \frac{21}{2} = \frac{21}{2} + \frac{21}{2} = 21$$

Question 25

Maths · Differential Equations · Numerical

Let the solution curve $y = y(x)$ of the differential equation $(4 + x^2)dy - 2x(x^2 + 3y + 4)dx = 0$ pass through the origin. Then $y(2)$ is equal to _______.

Answer: 12

Solution

Given the differential equation $(4 + x^2) dy - 2x(x^2 + 3y + 4) dx$. Rewriting, we have: $$(x^2 + 4) \frac{dy}{dx} = 2x^3 + 6xy + 8x$$ $$(x^2 + 4) \frac{dy}{dx} - 6xy = 2x^3 + 8x$$ This can be written as: $$\frac{dy}{dx} - \frac{6x}{x^2 + 4} y = \frac{2x^3 + 8x}{x^2 + 4}$$ This is a linear differential equation of the form $\frac{dy}{dx} + py = \phi$. The integrating factor is given by: $$e^{\log_e(x^2 + 4)^{-3}} = \frac{1}{(x^2 + 4)^3}$$ Solution: Multiply through by the integrating factor: $$\frac{1}{(x^2 + 4)^3} y = \int \frac{2x^3 + 8x}{(x^2 + 4)^3} (x^2 + 4) \, dx$$ Simplifying, we have: $$\frac{y}{(x^2 + 4)^3} = \int \frac{2x(x^2 + 4)}{(x^2 + 4)^3} \, dx$$ Let $x^2 + 4 = t$, then $2x \, dx = dt$. Thus, $$\frac{y}{(x^2 + 4)^3} = \int \frac{dt}{t^3}$$ Integrating, we get: $$\frac{y}{(x^2 + 4)^3} = \frac{-1}{2(x^2 + 4)^2} + C$$ Since the curve passes through the origin $(0, 0)$, $$0 = \frac{-1}{2 \times 16} + C$$ Solving for $C$, $$C = \frac{1}{32}$$ Thus, $$\frac{y}{(x^2 + 4)^3} = \frac{-1}{2(x^2 + 4)^2} + \frac{1}{32}$$ Simplifying, $$y = \frac{-(x^2 + 4)}{2} + \frac{(x^2 + 4)^3}{32}$$ Evaluating at $x = 2$, $$y(2) = -8 + \frac{8 \times 8 \times 8}{32}$$ $$y(2) = -8 + 16 = 8$$

Question 26

Maths · Trigonometric Functions · Numerical

If $\sin^2(10^\circ) \sin(20^\circ) \sin(40^\circ) \sin(50^\circ) \sin(70^\circ) = \alpha - \frac{1}{16} \sin(10^\circ)$, then $16 + \alpha^{-1}$ is equal to .

Answer: 80

Solution

Given $\sin 10^\circ \left( \frac{1}{2} \cdot 2 \sin 20^\circ \sin 40^\circ \right) \cdot \sin 10^\circ \sin(60^\circ - 10^\circ) \sin(60^\circ + 10^\circ)$. $$\sin 10^\circ \frac{1}{2} \left( \cos 20^\circ - \cos 60^\circ \right) \cdot \frac{1}{4} \sin 30^\circ$$ $$\frac{1}{2} \cdot \frac{1}{4} \cdot \frac{1}{2} \cdot \sin 10^\circ \left( \cos 20^\circ - \frac{1}{2} \right)$$ $$= \frac{1}{32} \left( 2 \sin 10^\circ \cos 20^\circ - \sin 10^\circ \right)$$ $$= \frac{1}{32} \left( \sin 30^\circ - \sin 10^\circ - \sin 10^\circ \right)$$ $$= \frac{1}{32} \left( \frac{1}{2} - 2 \sin 10^\circ \right)$$ $$= \frac{1}{64} \left( 1 - 4 \sin 10^\circ \right)$$ $$= \frac{1}{64} - \frac{1}{16} \sin 10^\circ$$ Hence $\alpha = \frac{1}{64}$

Question 27

Maths · Sets · Fill in the blank

Let A = $\{$ n $\in$ $\mathbb{N}$ : $\mathrm{H.C.F.}$ (n, 45) = 1 $\}$ and Let B = $\{$ 2k : k $\in$ $\{$ 1, 2, ..., 100 $\}$ $\}$. Then the sum of all the elements of A $\cap$ B is ________.

Answer: 5264

Solution

Sum of elements in $A \cap B$ $$= (2 + 4 + 6 + \ldots + 200) - (6 + 12 + \ldots + 198)$$ Multiple of 2, Multiple of 2 $\&$ 3 i.e. 6 $$- (10 + 20 + \ldots + 200) + (30 + 60 + \ldots + 180)$$ Multiple of 5 $\&$ 2 i.e. 10, Multiple of 2, 5 $\&$ 3 i.e. 30 $$= 5264$$

Question 28

Maths · Integrals · Numerical

The value of the integral $$\frac{48}{\pi^4} \int_{0}^{\pi} \left( \frac{3\pi x^2}{2} - x^3 \right) \frac{\sin x}{1 + \cos^2 x} \, dx$$ is equal to ________.

Answer: 6

Solution

Given $$I = \frac{48}{\pi^4} \int_0^\pi x^2 \left( \frac{3\pi}{2} - x \right) \frac{\sin x}{1 + \cos^2 x} \, dx \ldots (1)$$ Apply king property $$I = \frac{48}{\pi^4} \int_0^\pi (\pi - x)^2 \left( \frac{\pi}{2} + x \right) \frac{\sin x}{1 + \cos^2 x} \, dx \ldots (2)$$ (1) + (2) $$I = \frac{12}{\pi^3} \int_0^\pi \frac{\sin x}{1 + \cos^2 x} \left[ \pi^2 + (\pi - 2).x(\pi - 2x) \right] dx \ldots (3)$$ Apply king again $$I = \frac{12}{\pi^3} \int_0^\pi \frac{\sin x}{1 + \cos^2 x} \left[ \pi^2 + (\pi - 2)(\pi - x)(2x - \pi) \right] dx \ldots (4)$$ (3) + (4) $$I = \frac{6}{\pi^2} \int_0^\pi \frac{\sin x}{1 + \cos^2 x} \left[ 2\pi + (\pi - 2)(\pi - 2x) \right] dx \ldots (5)$$ Apply king $$I = \frac{6}{\pi^2} \int_0^\pi \frac{\sin x}{1 + \cos^2 x} \left[ 2\pi + (\pi - 2)(2x - \pi) \right] dx \ldots (6)$$ (5) + (6) $$I = \frac{12}{\pi} \int_0^\pi \frac{\sin x}{1 + \cos^2 x} \, dx$$ Let $\($ $\cos$ x = t $\Rightarrow$ $\sin$ x dx = -dt $\)$ $$I = \frac{12}{\pi} \int_1^{-1} \frac{-dt}{1 + t^2} = 6$$

Question 29

Maths · Sequences and Series · Numerical

Let $A = \sum_{i=1}^{10} \sum_{j=1}^{10} \min \{i,j\}$ and $B = \sum_{i=1}^{10} \sum_{j=1}^{10} \max \{i,j\}$. Then $A + B$ is equal to

Answer: 1100

Solution

Given $$A = \sum_{i=1}^{10} \sum_{j=1}^{10} \min \{i, j\}$$ $$B = \sum_{i=1}^{10} \sum_{j=1}^{10} \max \{i, j\}$$ For A: $$A = \sum_{j=1}^{10} \min(i, 1) + \min(j, 2) + \ldots + \min(i, 10)$$ $$= (1 + 1 + 1 + \ldots + 1)_{19 times} + (2 + 2 + \ldots + 2)_{17 times} + (3 + 3 + \ldots + 3)_{15 times}$$ $$+ \ldots + (1)_{1 time}$$ For B: $$B = \sum_{j=1}^{10} \max(i, 1) + \max(j, 2) + \ldots + \max(i, 10)$$ $$= (10 + 10 + \ldots + 10)_{19 times} + (9 + 9 + \ldots + 9)_{17 times} + \ldots + 1_{1 time}$$ Combining A and B: $$A + B = 20(1 + 2 + 3 + \ldots + 10)$$ $$= 20 \times \frac{10 \times 11}{2} = 10 \times 110 = 1100$$

Question 30

Maths · Differential Equations · Numerical

Let $S = (0, 2\pi) - \left\{ \frac{\pi}{2}, \frac{3\pi}{4}, \frac{3\pi}{2}, \frac{7\pi}{4} \right\}$. Let $y = y(x)$, $x \in S$, be the solution curve of the differential equation $\frac{dy}{dx} = \frac{1}{1 + \sin 2x}$, $y\left(\frac{\pi}{4}\right) = \frac{1}{2}$. If the sum of abscissas of all the points of intersection of the curve $y = y(x)$ with the curve $y = \sqrt{2} \sin x$ is $\frac{k\pi}{12}$, then $k$ is equal to .

Answer: 42

Solution

Given $\($ $\frac{dy}{dx}$ = $\frac{1}{1 + \sin 2x}$ $\)$. Integrating both sides, we have: $$ y(x) = -\frac{1}{1 + \tan x} + C $$ Given $\($ y$\left$( $\frac{\pi}{4}$ $\right$) = $\frac{1}{2}$ = -$\frac{1}{2}$ + C $\)$, we find $\($ C = 1 $\)$. Thus, $$ y(x) = \frac{-1}{1 + \tan x} + 1 $$ Simplifying, $$ y(x) = \frac{-1 + 1 + \tan x}{1 + \tan x} $$ $$ y(x) = \frac{\tan x}{1 + \tan x} $$ Solving with $\($ y = $\sqrt{2}$ $\sin$ x $\)$, $$ \frac{\tan x}{1 + \tan x} = \sqrt{2} \sin x $$ For $\($ $\sin$ x = 0 $\)$, $\($ $\frac{1}{\sqrt{2}}$ = $\sin$ x + $\cos$ x $\)$. Thus, $\($ x = $\pi$ $\)$ and $\($ $\frac{1}{2}$ = $\sin$ $\left$( x + $\frac{\pi}{4}$ $\right$) $\)$. Also, $\($ $\sin$ $\frac{\pi}{6}$ = $\sin$ $\left$( x + $\frac{\pi}{4}$ $\right$) $\)$. Therefore, $$ x + \frac{\pi}{4} = \pi - \frac{\pi}{6}, 2\pi + \frac{\pi}{6} $$ The sum of solutions is: $$ x = \frac{5\pi}{12}, \frac{13\pi}{12} - \frac{\pi}{12} $$ Thus, $$ = \pi + \frac{7\pi}{12} + \frac{23\pi}{12} $$ $$ = \frac{12\pi + 7\pi + 23}{12} = \frac{42\pi}{12} = \frac{k\pi}{12} $$ Therefore, $\($ k = 42 $\)$.

Physics

Question 31

Physics · Physical World, Units and Measurements · Single correct

An expression for a dimensionless quantity P is given by $P = \frac{\alpha}{\beta} \log_e \left( \frac{kt}{\beta x} \right)$; where $\alpha$ and $\beta$ are constants, $x$ is distance; $k$ is Boltzmann constant and $t$ is the temperature. Then the dimensions of $\alpha$ will be:

  1. $[M^0L^{-1}T^0]$
  2. $[ML^0T^{-2}]$
  3. $[MLT^{-2}]$
  4. $[ML^2T^{-2}]$

Answer: (c)

Solution

Given $P = \frac{\alpha}{\beta} \log_e \left( \frac{kt}{\beta x} \right)$. $$\frac{kt}{\beta x} = 1 \implies \beta = \frac{kt}{x} = \frac{\mathrm{ML}^2 \mathrm{T}^{-2}}{\mathrm{L}}$$ Therefore, $E = \frac{1}{2} kt$. As $P$ is dimensionless, $$\Rightarrow [\alpha] = [\beta] = [\mathrm{MLT}^{-2}]$$

Question 32

Physics · Motion in a Straight Line · Single correct

A person is standing in an elevator. In which situation, he experiences weight loss?

  1. When the elevator moves upward with constant acceleration
  2. When the elevator moves downward with constant acceleration
  3. When the elevator moves upward with uniform velocity
  4. When the elevator moves downward with uniform velocity

Answer: (b)

Solution

Given the forces acting on the person in the lift, we have: $$mg - N = ma$$ Solving for $N$, we get: $$N = m(g - a)$$ Therefore, the person experiences weight loss when the acceleration of the lift is downward.

Question 33

Physics · Motion in a Straight Line · Single correct

An object is thrown vertically upwards. At its maximum height, which of the following quantity becomes zero?

  1. Momentum
  2. Potential energy
  3. Acceleration
  4. Force

Answer: (a)

Solution

At maximum height, $V = 0$. Therefore, the momentum of the object is zero.

Question 34

Physics · Laws of Motion · Single correct

A ball is released from rest from point P of a smooth semi-spherical vessel as shown in figure. The ratio of the centripetal force and normal reaction on the ball at point Q is A while angular position of point Q is $\alpha$ with respect to point P. Which of the following graphs represent the correct relation between A and $\alpha$ when ball goes from Q to R?

Answer: (c)

Solution

Given $V = \sqrt{2gR \sin \alpha}$. $N - mg \sin \alpha = \frac{mv^2}{R} = 2mg \sin \alpha$ $$\frac{N}{2mg \sin \alpha} = \frac{1}{2} + 1 = \frac{3}{2}$$ Therefore, $A = constant$.

Question 35

Physics · System of Particles and Rotational Motion · Single correct

A thin circular ring of mass M and radius R is rotating with a constant angular velocity 2 rads$^{-1}$ in a horizontal plane about an axis vertical to its plane and passing through the center of the ring. If two objects each of mass m be attached gently to the opposite ends of a diameter of ring, the ring will then rotate with an angular velocity (in rads$^{-1}$).

  1. $\frac{M}{(M + m)}$
  2. $\frac{(M + 2m)}{2M}$
  3. $\frac{2M}{(M + 2m)}$
  4. $\frac{2(M + 2m)}{M}$

Answer: (c)

Solution

Applying conservation of angular momentum $$MR^2 \omega = (MR^2 + 2mR^2) \omega'$$ $$\omega' = \frac{2M}{M + 2m}$$

Question 36

Physics · Gravitation · Single correct

The variation of acceleration due to gravity ($g$) with distance ($r$) from the center of the earth is correctly represented by: (Given $R =$ radius of earth)

Answer: (a)

Solution

The gravitational field strength $g$ is given by the piecewise function: $$g = \begin{cases} \frac{GMr}{R^3}, & r \leq R \\ \frac{GM}{r^2}, & r \geq R \end{cases}$$ The graph shows $g$ as a function of $r$, with a linear increase up to $R$ and a decrease following an inverse square law beyond $R$.

Question 37

Physics · Thermodynamics · Single correct

The efficiency of a Carnot's engine, working between steam point and ice point, will be:

  1. 26.81$\%$
  2. 37.81$\%$
  3. 47.81$\%$
  4. 57.81$\%$

Answer: (c)

Solution

The period is given by the formula $$T = 2\pi \sqrt{\frac{\ell}{g_{eff}}}$$. (a) When $a = 0$, the period is $$T = 2\pi \sqrt{\frac{\ell}{g}}$$. (b) When $a = \frac{g}{6}$, the period is $$T' = 2\pi \sqrt{\frac{\ell}{g + \frac{g}{6}}}$$. Therefore, $$T' = \sqrt{\frac{6}{7}} T$$.

Question 38

Physics · Oscillations · Single correct

Time period of a simple pendulum in a stationary lift is $T$. If the lift accelerates with $\frac{g}{6}$ vertically upwards then the time period will be : (where $g =$ acceleration due to gravity)

  1. $\sqrt{\frac{6}{5}} T$
  2. $\sqrt{\frac{5}{6}} T$
  3. $\sqrt{\frac{6}{7}} T$
  4. $\sqrt{\frac{7}{6}} T$

Answer: (c)

Solution

Question 39

Physics · Thermodynamics · Single correct

A thermally insulated vessel contains an ideal gas of molecular mass $M$ and ratio of specific heats 1.4. Vessel is moving with speed $v$ and is suddenly brought to rest. Assuming no heat is lost to the surrounding and vessel temperature of the gas increases by : (R = universal gas constant)

  1. $\frac{Mv^2}{7R}$
  2. $\frac{Mv^2}{5R}$
  3. $\frac{2Mv^2}{7R}$
  4. $\frac{7Mv^2}{5R}$

Answer: (b)

Solution

Question 40

Physics · Electrostatic Potential and Capacitance · Single correct

Two capacitors having capacitance $C_1$ and $C_2$ respectively are connected as shown in figure. Initially, capacitor $C_1$ is charged to a potential difference $V$ volt by a battery. The battery is then removed and the charged capacitor $C_1$ is now connected to uncharged capacitor $C_2$ by closing the switch $S$. The amount of charge on the capacitor $C_2$, after equilibrium is:

  1. $\frac{C_1 C_2}{C_1 + C_2} V$
  2. $\frac{(C_1 + C_2)}{C_1 C_2} V$
  3. $(C_1 + C_2) V$
  4. $(C_1 - C_2) V$

Answer: (a)

Solution

Charge on capacitor $C_2$ $$= \frac{C_2 \times Q_{total}}{C_{total}} = \frac{C_2 [C_1 V]}{C_1 + C_2} = \frac{C_1 C_2 V}{C_1 + C_2}$$

Question 41

Physics · Magnetism and Matter · Single correct

Assertion (A) : Non-polar materials do not have any permanent dipole moment. Reason (R) : When a non-polar material is placed in an electric field, the centre of the positive charge distribution of its individual atom or molecule coincides with the centre of the negative charge distribution. In the light of above statements, choose the most appropriate answer from the options given below.

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

Answer: (c)

Solution

S1: In nonpolar molecules, centre of positive charge coincides with centre of negative charge, hence net dipole moment comes to zero. S2: When nonpolar material is placed in external field, centre of charges does not coincide, hence gives non-zero moment in field.

Question 42

Physics · Electromagnetic Induction · Single correct

The magnetic flux through a coil perpendicular to its plane is varying according to the relation $\phi = (5t^3 + 4t + 2t - 5)$ Weber. If the resistant of the coil is $5 \, \mathrm{ohm}$, then the induced current through the coil at $t = 2 \, \mathrm{sec}$ will be:

  1. 15.6 A
  2. 16.6 A
  3. 17.6 A
  4. 18.6 A

Answer: (a)

Solution

Given $\phi = 5t^3 + 4t^2 + 2t - 5$. The magnitude of $e$ is given by $\left| e \right| = \left| \frac{d\phi}{dt} \right| = 15t^2 + 8t + 2$. At $t = 2$, $\left| e \right| = 15 \times 2^2 + 8 \times 2 + 2$. Therefore, $e = 78 \, \mathrm{V}$ implies $I = \frac{e}{R} = \frac{78}{5} = 15.60$.

Question 43

Physics · Current Electricity · Single correct

An aluminium wire is stretched to make its length, 04$\%$ larger. Then percentage change in resistance is:

  1. 0.4 $\%$
  2. 0.2 $\%$
  3. 0.8 $\%$
  4. 0.6 $\%$

Answer: (c)

Solution

Given the formula for resistance, $$R = \frac{\rho \ell}{A}$$ we have the relative change in resistance as $$\frac{\Delta R}{R} = \frac{\Delta \ell}{\ell} - \frac{\Delta A}{A}$$ Given that $$\ell A = k$$ we have $$\frac{\Delta \ell}{\ell} + \frac{\Delta A}{A} = 0$$ Therefore, $$\frac{\Delta R}{R} = \frac{2 \Delta \ell}{\ell}$$ Substituting the given values, $$\frac{\Delta R}{R} = 2 \times 0.4 = 0.8\%$$

Question 44

Physics · Moving Charges and Magnetism · Single correct

A proton and an alpha particle of the same enter in a uniform magnetic field which is acting perpendicular to their direction of motion. The ratio of the circular paths described by the alpha particle and proton is:

  1. 1 : 4
  2. 4 : 1
  3. 2 : 1
  4. 1 : 2

Answer: (c)

Solution

Given $\($ $\frac{R_{\alpha}}{R_{P}}$ = $\frac{M_{\alpha}}{M_{P}}$ $\times$ $\frac{q_{P}}{q_{\alpha}}$ $\)$. $\($ $\frac{R_{\alpha}}{R_{P}}$ = $\frac{4}{1}$ $\times$ $\frac{1}{2}$ = 2 $\)$

Question 45

Physics · Electromagnetic Waves · Single correct

If electric field intensity of a uniform plane electro magnetic wave is given as $$\mathbf{E} = -301.6 \sin(kz - \omega t) \hat{a}_x + 452.4 \sin(kz - \omega t) \hat{a}_y \frac{\mathrm{V}}{\mathrm{m}}$$ Then, magnetic intensity $\mathbf{H}$ of this wave in $\mathrm{Am}^{-1}$ will be: [Given: Speed of light in vacuum $c = 3 \times 10^8 \, \mathrm{ms}^{-1}$, permeability of vacuum $\mu_0 = 4\pi \times 10^{-7} \, \mathrm{NA}^{-2}$]

  1. $+0.8 \sin(kz - \omega t) \hat{a}_y + 0.8 \sin(kz - \omega t) \hat{a}_x$
  2. $+1.0 \times 10^{-6} \sin(kz - \omega t) \hat{a}_y + 1.5 \times 10^{-6} (kz - \omega t) \hat{a}_x$
  3. $-0.8 \sin(kz - \omega t) \hat{a}_y - 1.2 \sin(kz - \omega t) \hat{a}_x$
  4. $-1.0 \times 10^{-6} \sin(kz - \omega t) \hat{a}_y - 1.5 \times 10^{-6} \sin(kz - \omega t) \hat{a}_x$

Answer: (c)

Solution

Given $\($ $\mathbf{E}$ = 301.6 $\sin$ (kz - $\omega$ t)(-$\hat{a}$_x) + 452.4 $\sin$ (kz - $\omega$ t) $\hat{a}$_y $\)$. $\($ $\mathbf{B}$ = $\frac{301.6}{C}$ $\sin$ (kz - $\omega$ t)(-$\hat{a}$_y) + $\frac{452.4}{C}$ $\sin$ (kz - $\omega$ t)(-$\hat{a}$_x) $\)$. $\($ $\mathbf{H}$ = $\frac{\mathbf{B}}{\mu_0}$ = $\frac{301.6}{\mu C}$ $\sin$ (kz - $\omega$ t)(-$\hat{a}$_y) + $\frac{452.4}{\mu C}$ $\sin$ (kz - $\omega$ t)(-$\hat{a}$_x) $\)$. $\($ $\mathbf{H}$ = -0.8 $\sin$ (kz - $\omega$ t) $\hat{a}$_y - 1.2 $\sin$ (kz - $\omega$ t) $\hat{a}$_x $\)$. For direction $\($ $\mathbf{E}$ $\times$ $\mathbf{B}$ $\)$ is direction of $\($ $\mathbf{C}$ $\)$. For first part $\($ $\hat{E}$ = -$\hat{i}$, $\hat{B}$ = ? $\)$ $\($ $\hat{E}$ $\times$ $\hat{B}$ = $\hat{k}$ $\Rightarrow$ $\hat{B}$ = -$\hat{j}$ $\)$ Similarly for second $\($ $\hat{E}$ = $\hat{j}$, $\hat{B}$ = ? $\)$ $\($ $\hat{E}$ $\times$ $\hat{B}$ = $\hat{k}$ $\Rightarrow$ $\hat{B}$ = -$\hat{i}$ $\)$

Question 46

Physics · Wave Optics · Single correct

In free space, an electromagnetic wave of 3 GHz of 3 GHz frequency strikes over the edge of an object of size $\frac{\lambda}{100}$, where $\lambda$ is the wavelength of the wave in free space. The phenomenon, which happens there will be:

  1. Reflection
  2. Refraction
  3. Diffraction
  4. Scattering

Answer: (d)

Solution

For reflection, size of obstacle must be much larger than wavelength, for diffraction size should be order of wavelength. Since the object is of size $\frac{\lambda}{100}$, much smaller than wavelength, so scattering will occur.

Question 47

Physics · Dual Nature of Radiation and Matter · Single correct

An electron with speed $v$ and a photon with speed $c$ have the same de-Broglie wavelength. If the kinetic energy and momentum of electron are $E_e$ and $p_e$ and that of photon are $E_{ph}$ and $p_{ph}$ respectively. Which of the following is correct?

  1. $\frac{E_e}{E_{ph}} = \frac{2c}{v}$
  2. $\frac{E_e}{E_{ph}} = \frac{v}{2c}$
  3. $\frac{p_e}{p_{ph}} = \frac{2c}{v}$
  4. $\frac{p_e}{p_{ph}} = \frac{v}{2c}$

Answer: (b)

Solution

Given $\lambda_e = \lambda_{photon}$. $$\frac{h}{mv} = \frac{h}{P_{photon}} \implies P_{photon} = mv$$ $$\frac{E_e}{E_{ph}} = \frac{\frac{1}{2}mv^2}{\frac{hc}{\lambda}} = \frac{1}{2} \frac{mv}{P_{ph} C} \times v = \frac{v}{2C}$$

Question 48

Physics · Nuclei · Single correct

How many alpha and beta particles are emitted when Uranium $_{92}^{238}\mathrm{U}$ decays to lead $_{82}^{206}\mathrm{Pb}$?

  1. 3 alpha particles and 5 beta particles
  2. 6 alpha particles and 4 beta particles
  3. 4 alpha particles and 5 beta particles
  4. 8 alpha particles and 6 beta particles

Answer: (d)

Solution

The reaction is given by: $$^{238}_{92} \mathrm{U} \rightarrow \boxed{8} \; ^{4}_{2} \mathrm{He} + \boxed{6} \; ^{0}_{-1} \mathrm{e} + ^{206}_{82} \mathrm{Pb}$$ 8 $\alpha$ particles and 6 $\beta$ particles are emitted.

Question 49

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

The I-V characteristics of a p-n junction diode in forward bias is shown in the figure. The ratio of dynamic resistance, corresponding to forward bias voltages of 2V and 4V respectively, is:

  1. 1 : 2
  2. 5 : 1
  3. 1 : 40
  4. 20 : 1

Answer: (b)

Solution

Given the formula for resistance, $R = \frac{\Delta V}{\Delta i}$. We have: $$\frac{R_1}{R_2} = \frac{\Delta v_1}{\Delta v_2} \frac{\Delta i_2}{\Delta i_1} = \frac{0.1}{0.2} \times \frac{50}{5} = 5$$

Question 50

Physics · Communication Systems · Single correct

Choose the correct statement for amplitude modulation:

  1. Amplitude of modulating is varied in accordance with the information signal.
  2. Amplitude of modulated is varied in accordance with the information signal.
  3. Amplitude of carrier signal is varied in accordance with the information signal.
  4. Amplitude of modulated is varied in accordance with the modulating signal.

Answer: (c)

Solution

In amplitude modulation, the amplitude of high frequency carrier wave is varied in accordance with message signal.

Question 51

Physics · Motion in a Plane · Numerical

A fighter jet is flying horizontally at a certain altitude with a speed of $200 \, \mathrm{m/s}$. When it passes directly overhead an anti-aircraft gun, bullet is fired from the gun, at an angle $\theta$ with the horizontal, to hit the jet. If the bullet speed is $400 \, \mathrm{m/s}$, the value of $\theta$ will be .......... $^\circ$.

Answer: 60

Solution

Both should have same horizontal component of velocity. $$200 = 400 \cos \theta$$ $$\theta = 60^\circ$$

Question 52

Physics · Motion in a Straight Line · Numerical

A ball of mass $0.5 \, \mathrm{kg}$ is dropped from the height of $10 \, \mathrm{m}$. The height, at which the magnitude of velocity becomes equal to the magnitude of acceleration due to gravity, is .............. m. (Use $g = 10 \, \mathrm{m/s^2}$).

Answer: 5

Solution

Given $v^2 = u^2 + 2as$. $$100 = 0 + 2(10)s$$ Therefore, $S = 5 \, \mathrm{m}$. Height from ground $= 10 - 5 = 5 \, \mathrm{m}$.

Question 53

Physics · Mechanical Properties of Solids · Numerical

The elastic behaviour of material for linear stress and linear strain, is shown in the figure. The energy density for a linear strain of $5 \times 10^{-4}$ is ............ $\mathrm{kJ/m^3}$. Assume that material is elastic upto the linear strain of $5 \times 10^{-4}$.

Answer: 25

Solution

Given $\($ y = $\frac{stress}{strain}$ = 2.0 $\times$ 10^{10} $\)$. Energy density = $\($ $\frac{1}{2}$ stress $\times$ strain $\)$ $\[$ = $\frac{1}{2}$ (strain)^2 $\cdot$ y = $\frac{1}{2}$ (5 $\times$ 10^{-4})^2 $\times$ 20 $\times$ 10^{10} $\]$ $\[$ = 25 $\times$ 10^2 $\times$ 10 = 25 $\frac{kJ}{m^3}$ $\]$ Ans. 25

Question 54

Physics · Gravitation · Numerical

The elongation of a wire on the surface of the earth is $10^{-4} \, \mathrm{m}$. The same wire of same dimensions is elongated by $6 \times 10^{-5} \, \mathrm{m}$ on another planet. The acceleration due to gravity on the planet will be ............ $\mathrm{ms^{-2}}$. (Take acceleration due to gravity on the surface of earth = $10 \, \mathrm{m/s^{2}}$)

Answer: 6

Solution

Given $\Delta \ell \propto g$. $$\frac{\Delta \ell_{earth}}{\Delta \ell_{planet}} = \frac{g_{earth}}{g_{planet}} = \frac{10^{-4}}{6 \times 10^{-5}}$$ Therefore, $g_{planet} = 6 \, \mathrm{m/s^2}$.

Question 55

Physics · Electromagnetic Induction · Numerical

A $10\,\Omega$, $20\,\mathrm{mH}$ coil carrying constant current is connected to a battery of $20\,\mathrm{V}$ through a switch is opened current becomes zero in $100\mu\mathrm{s}$. The average emf induced in the coil is $\ldots$ V.

Answer: 400

Solution

Question 56

Physics · Ray Optics and Optical Instruments · Numerical

A light ray is incident, at an incident angle $\theta_1$, on the system of two plane mirrors $M_1$ and $M_2$ having an inclination angle $75^\circ$ between them (as shown in figure). After reflecting from mirror $M_1$ it gets reflected back by the mirror $M_2$ with an angle of reflection $30^\circ$. The total deviation of the ray will be ............. degree.

Answer: 210

Solution

Given $\delta_{total} = 360^\circ - 2\theta$. $$= 360^\circ - 2 \times 75^\circ$$ $$\delta_{total} = 210^\circ$$ From the diagram, $\theta_1 = 45^\circ$. In the second diagram, $\delta = 120^\circ + 90^\circ = 210^\circ$.

Question 57

Physics · Experimental Physics · Numerical

In a vernier callipers, each cm on the main scale is divided into 20 equal parts. If tenth vernier scale division coincides with nineth main scale division. Then the value of vernier constant will be ............. $\times 10^{-2} \, \mathrm{mm}$.

Answer: 5

Solution

20 MSD = 1 cm 1 MSD = $\frac{1}{20}$ cm 10 VSD = 9 MSD 1 VSD = $\frac{9}{10}$ MSD = $\frac{9}{10}$ $\times$ $\frac{1}{20}$ cm 1 VSD = $\frac{9}{200}$ cm VC = 1 MSD - 1 VSD = $\frac{1}{20}$ cm - $\frac{9}{200}$ cm = $\frac{1}{200}$ $\times$ 10 mm VC = 5 $\times$ 10^{-2} mm Ans. 5

Question 58

Physics · Semiconductor Electronics: Materials, Devices and Simple Circuits · Numerical

As per the given circuit, the value of current through the battery will be .......... A.

Answer: 1

Solution

Given $V = IR_{net}$. $$10 = I \times 10$$ Therefore, $I = 1 \, \mathrm{A}$. Ans. 1

Question 59

Physics · Alternating Current · Numerical

A 110 V , 50 Hz, AC source is connected in the circuit (as shown in figure). The current through the resistance 55 Ω, at resonance in the circuit, will be .............. A.

Answer: 0

Solution

At resonance $I_L = I_C$. Alternatively, $$\frac{1}{Z} = \sqrt{\left(\frac{1}{X_L} - \frac{1}{X_C}\right)^2}$$ At resonance, $X_L = X_C$ and $Z \to \infty$. Therefore, $Z_{total circuit} \to \infty$, i.e., $I = 0$. Ans. 0

Question 60

Physics · Mechanical Properties of Fluids · Numerical

An ideal fluid of density $800 \, \mathrm{kgm^{-3}}$, flows smoothly through a bent pipe (as shown in figure) that tapers in cross-sectional area from $a$ to $\frac{a}{2}$. The pressure difference between the wide and narrow sections of pipe is $4100 \, \mathrm{Pa}$. At wider section, the velocity of fluid is $\frac{\sqrt{x}}{6} \, \mathrm{ms^{-1}}$ for $x = \ldots\ldots\ldots\ldots\ldots\ldots\ldots\ldots\ldots$. (Given $g = 10 \, \mathrm{m^{2}}$)

Answer: 363

Solution

From continuity equation $$a v_1 = \frac{a}{2} v_2$$ $$v_2 = 2 v_1$$ From Bernoulli's theorem, $$P_1 + \rho g h_1 + \frac{1}{2} \rho v_1^2 = P_2 + \rho g h_2 + \frac{1}{2} \rho v_2^2$$ $$P_1 - P_2 = \rho \left[ \frac{v_2^2 - v_1^2}{2} + g(h_2 - h_1) \right]$$ $$4100 = 800 \left[ \frac{4 v_1^2 - v_1^2}{2} \right] + 10 \times (0 - 1)$$ $$\frac{41}{8} + 10 = \frac{3 v_1^2}{2}$$ $$\frac{121}{8} \times \frac{2}{3} = v_1^2$$ $$v_1 = \sqrt{\frac{121}{4 \times 3} \times \frac{3}{3}}$$ $$v_1 = \frac{\sqrt{363}}{6} \, \mathrm{m/s}$$ $$X = 363.$$

Chemistry

Question 61

Chemistry · Some Basic Concepts of Chemistry · Single correct

A commercially sold conc. HCl is 35$\%$ HCl by mass. If the density of this commercial acid is 1.46 $\mathrm{g/mL}$, the molarity of this solution is : (Atomic mass : $\mathrm{Cl}$ = 35.5 $\mathrm{amu}$, $\mathrm{H}$ = 1 $\mathrm{amu}$)

  1. 10.2 $\mathrm{M}$
  2. 12.5 $\mathrm{M}$
  3. 14.0 $\mathrm{M}$
  4. 18.2 $\mathrm{M}$

Answer: (c)

Solution

Let total volume = 1000 $\mathrm{mL}$ = 1 $\mathrm{L}$. Total mass of solution = 1460 $\mathrm{g}$. Mass of $\mathrm{HCl}$ = $\frac{35}{100}$ $\times$ 1460. Moles of $\mathrm{HCl}$ = $\frac{35 \times 1460}{100 \times 36.5}$. So molarity = $\frac{35 \times 1460}{100 \times 36.5}$ = 14 $\mathrm{M}$.

Question 62

Chemistry · States of Matter · Single correct

An evacuated glass vessel weighs 40.0 $\mathrm{g}$ when empty, 135.0 $\mathrm{g}$ when filled with a liquid of density 0.95 $\mathrm{g}$ \, $\mathrm{mL}^{-1}$ and 40.5 $\mathrm{g}$ when filled with an ideal gas at 0.82 $\mathrm{atm}$ at 250 $\mathrm{K}$. The molar mass of the gas in $\mathrm{g}$ \, $\mathrm{mol}^{-1}$ is: (Given : R = 0.082 \, $\mathrm{L}$ \, $\mathrm{atm}$ \, $\mathrm{K}^{-1}$ \, $\mathrm{mol}^{-1}$)

  1. 35
  2. 50
  3. 75
  4. 125

Answer: (d)

Solution

Mass of liquid $=135-40=95\,\mathrm{g}$ Volume of liquid $=\frac{\text{mass}}{\text{density}}=\frac{95}{0.95}\,\mathrm{mL}=100\,\mathrm{mL}=0.1\,\mathrm{L}$ Mass of ideal gas $=40.5-40\,\mathrm{g}=0.5\,\mathrm{g}$ $PV=nRT$ $0.82\times0.1=\left(\frac{0.5}{M}\right)\times0.082\times250$ $M=125$

Question 63

Chemistry · Structure of Atom · Single correct

If the radius of the 3rd Bohr's orbit of hydrogen atom is $r_3$ and the radius of 4th Bohr's orbit is $r_4$. Then:

  1. $r_4 = \frac{9}{16} r_3$
  2. $r_4 = \frac{16}{9} r_3$
  3. $r_4 = \frac{3}{4} r_3$
  4. $r_4 = \frac{4}{3} r_3$

Answer: (b)

Solution

Given the formula for the radius: $$r = 0.529 \times \frac{n^2}{z} \, Å$$ Calculate $r_3$: $$r_3 = 0.529 \times \frac{3^2}{1}$$ Calculate $r_4$: $$r_4 = 0.529 \times \frac{4^2}{1}$$ The ratio $\frac{r_4}{r_3}$ is: $$\frac{r_4}{r_3} = \frac{4^2}{3^2} = \frac{16}{9}$$ Thus, $$r_4 = \frac{16r_3}{9}$$

Question 64

Chemistry · Chemical Bonding and Molecular Structure · Single correct

Consider the ions/molecule $O_2^+$, $O_2$, $O_2^-$, $O_2^{2-}$ For increasing bond order the correct option is:

  1. $O_2^{2-} < O_2^- < O_2 < O_2^+$
  2. $O_2^- < O_2^{2-} < O_2 < O_2^+$
  3. $O_2^- < O_2^{2-} < O_2^+ < O_2
  4. $O_2^- < O_2^+ < O_2^{2-} < O_2

Answer: (a)

Solution

\begin{tabular}{|l|c|c|c|} \hline \textbf{ion/molecule} & \textbf{Number of $e^-$ in BMO} & \textbf{Number of $e^-$ in ABMO} & \textbf{Bond order} \\ \hline O$_2^+$ & 10 & 5 & 2.5 \\ \hline O$_2$ & 10 & 6 & 2 \\ \hline O$_2^-$ & 10 & 7 & 1.5 \\ \hline O$_2^{2-}$ & 10 & 8 & 1 \\ \hline \end{tabular} Bond order $O_2^{2-}<O_2^-<O_2<O_2^+$

Question 65

Chemistry · Electrochemistry · Single correct

The $\left(\frac{\partial E}{\partial T}\right)_P$ values of different types of half-cells are as follows: A: $1\times10^{-4}$ B: $2\times10^{-4}$ C: $0.1\times10^{-4}$ D: $0.2\times10^{-4}$ (Where $E$ is the electromotive force.) Which of the above half-cells would be preferred for use as a reference electrode?

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

Answer: (c)

Solution

A cell with less variation in EMF with temperature is preferred as a reference electrode because it can be used over a wider temperature range without much deviation from its standard value. Therefore, a cell with a smaller value of $\left(\frac{\partial E}{\partial T}\right)_P$ is preferred.

Question 66

Chemistry · The p-Block Elements (Group-13 and 14) · Single correct

Choose the correct stability order of group 13 elements in their +1 oxidation state.

  1. Al < Ga < In < Tl
  2. Tl < In < Ga < Al
  3. Al < Ga < Tl < In
  4. Al < Tl < Ga < In

Answer: (a)

Solution

Moving down the group, stability of lower oxidation state increases. $$\mathrm{Al} < \mathrm{Ga} < \mathrm{In} < \mathrm{Tl}$$

Question 67

Chemistry · General Principles and Processes of Isolation of Elements · Single correct

Given below are two statements : Statement I : According to the Ellingham diagram, any metal oxide with higher $\Delta G^\circ$ is more stable than the one with lower $\Delta G^\circ$. Statement II : The metal involved in the formation of oxide placed lower in the Ellingham diagram can reduce the oxide of a metal placed higher in the diagram. In the light of the above statements, choose the most appropriate answer from the options given below :

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

Answer: (d)

Solution

Metal oxide with lower $\Delta G^\circ$ is more stable. Statement II is correct.

Question 68

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

Consider the following reaction: $$2\mathrm{HSO}_4^- (\mathrm{aq}) \xrightarrow{(1) Electrolysis \atop (2) Hydrolysis} 2\mathrm{HSO}_4^- + 2\mathrm{H}^+ + \mathrm{A}$$ The dihedral angle in product A in its solid phase at 110 K is:

  1. $104^\circ$
  2. $111.5^\circ$
  3. $90.2^\circ$
  4. $111.0^\circ$

Answer: (c)

Solution

The reaction involves electrolysis and hydrolysis of $2\mathrm{HSO_4^- (aq.)}$ to form $2\mathrm{HSO_4^-} + 2\mathrm{H^+} + \mathrm{H_2O_2}$. The structure shown is a solid phase with an angle of $90.2^\circ$.

Question 69

Chemistry · The s-Block Elements · Single correct

The correct order of melting point is :

  1. Be > Mg > Ca > Sr
  2. Sr > Ca > Mg > Be
  3. Be > Ca > Mg > Sr
  4. Be > Ca > Sr > Mg

Answer: (d)

Solution

The melting points (M.P) of the elements are given as follows: Beryllium (Be): $1560 \, \mathrm{K}$ Magnesium (Mg): $924 \, \mathrm{K}$ Calcium (Ca): $1124 \, \mathrm{K}$ Strontium (Sr): $1062 \, \mathrm{K}$

Question 70

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

The correct order of melting points of hydrides of group 16 elements is :

  1. H_2S < H_2Se < H_2Te < H_2O
  2. H_2O < H_2S < H_2Se < H_2Te
  3. H_2S < H_2Te < H_2Se < H_2O
  4. H_2Se < H_2S < H_2Te < H_2O

Answer: (a)

Solution

\begin{tabular}{|l|c|} \hline \textbf{Hydride} & \textbf{M.P.} \\ \hline H$_2$O & 273 K \\ \hline H$_2$S & 188 K \\ \hline H$_2$Se & 208 K \\ \hline H$_2$Te & 222 K \\ \hline \end{tabular}

Question 71

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

Consider the following reaction: A + alkali $\rightarrow$ B (Major Product) If B is an oxoacid of phosphorus with no P–H bond, then A is:

  1. White $P_4$
  2. Red $P_4$
  3. $P_2O_3$
  4. $H_3PO_3$

Answer: (b)

Solution

White $\mathrm{P_4}$ + alkali $\rightarrow \mathrm{H_3PO_2}$ Red $\mathrm{P_4}$ + alkali $\rightarrow \mathrm{H_4P_2O_6}$

Question 72

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

Polar stratospheric clouds facilitate the formation of:

  1. ClONO_2
  2. HOCl
  3. ClO
  4. CH_4

Answer: (b)

Solution

Polar stratospheric clouds provide surface on which hydrolysis of $\mathrm{ClONO_2}$ takes place to form $\mathrm{HOCl}$ (Hypochlorous acid). $$\mathrm{ClONO_2(g) + H_2O(g) \rightarrow HOCl(g) + HNO_3(g)}$$

Question 73

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

Given below are two statements : Statement I : In 'Lassaigne's Test, when both nitrogen and sulphur are present in an organic compound, sodium thiocyanate is formed. Statement II : If both nitrogen and sulphur are present in an organic compound, then the excess of sodium used in sodium fusion will decompose the sodium thiocyanate formed to give NaCN and $Na_2S$. In the light of the above statements, choose the most appropriate answer from the options given below :

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

Answer: (a)

Solution

Both statement I and statement II are correct.

Question 74

Chemistry · Alcohols, Phenols and Ethers · Single correct

$(C_7H_5O_2)_2$ $\xrightarrow{h\nu}$ $[X]+2\,\overset{\bullet}{C_6H_5}+2CO_2$ Consider the above reaction and identify the intermediate 'X'

  1. C_6H_5-$\overset{\oplus}{\mathrm{C}}$=O
  2. C_6H_5-$\overset{\ominus}{\mathrm{C}}$=O

Answer: (d)

Solution

The reaction involves the photochemical decomposition of a peroxide compound. Upon exposure to light $h\nu$, the peroxide bond breaks, leading to the formation of a phenyl radical and a benzoate radical. The benzoate radical further decomposes to form a phenyl radical and carbon dioxide $\mathrm{CO_2}$. The overall reaction results in the formation of two phenyl radicals and the release of $\mathrm{CO_2}$.

Question 75

Chemistry · Aldehydes, Ketones and Carboxylic Acids · Single correct

Consider the above reaction sequence and identify the product $\textbf{B}$.

Answer: (a)

Solution

Although Acetyl Acetone predominantly gives Acid base reaction with G.R due to Active methylene group but according to given option ans should be based on nucleophilic addition reaction (NAR).

Question 76

Chemistry · Aldehydes, Ketones and Carboxylic Acids · Single correct

Which will have the highest enol content?

Answer: (c)

Solution

The compound on the left is a tautomer of the compound on the right, which is aromatic in nature.

Question 77

Chemistry · Amines · Single correct

Among the following structures, which will show the most stable enamine formation? (Where Me is $-\mathrm{CH}_3$)

Answer: (c)

Solution

All these enamines are interconvertible through their resonating structures. So most stable form is 'C' due to steric factor.

Question 78

Chemistry · Polymers · Single correct

Which of the following sets are correct regarding polymer ? (A) Copolymer : Buna–S (B) Condensation polymer : Nylon–6,6 (C) Fibre : Nylon–6,6 (D) Thermosetting polymer : Terylene (E) Homopolymer : Buna–N Choose the correct answer from given options below:

  1. (A), (B) and ( C ) are correct
  2. (B), ( C ) and (D) are correct
  3. (A), ( C ) and (E) are correct
  4. (A), (B) and (D) are correct

Answer: (a)

Solution

Which of the following set are correct regarding polymer. Bona - 5 is copolymer of butadiene + styrene Nylon 6.6 is condensation polymer of adipic Acid and hexanediamine. Nylon 6.6 is fiber Terylene is fiber not thermosetting polymer Buna-N is copolymer not Homopolymer

Question 79

Chemistry · Chemistry in Everyday Life · Single correct

A chemical which stimulates the secretion of pepsin is :

  1. Anti histamine
  2. Cimetidine
  3. Histamine
  4. Zantac

Answer: (c)

Solution

Histamine (It is used for secretion of pepsin & HCl in stomach)

Question 80

Chemistry · Co-ordination Compounds · Single correct

Which statement is not true with respect to nitrate ion test?

  1. A dark brown ring is formed at the junction of two solutions.
  2. Ring is formed due to nitroferrous sulphate complex.
  3. The brown complex is $[\mathrm{Fe(H_2O)_5(NO)]SO_4}$.
  4. Heating the nitrate salt with conc. $\mathrm{H_2SO_4}$, light brown fumes are evolved.

Answer: (b)

Solution

Ring is formed due to formation of nitrosoferrous sulphate.

Question 81

Chemistry · Thermodynamics · Numerical

For complete combustion of methanol $\mathrm{CH_3OH}(l)$+$\frac{3}{2}\mathrm{O_2}(g)$ $\rightarrow$ $\mathrm{CO_2}(g)$+$2\mathrm{H_2O}(l)$ the amount of heat produced as measured by bomb calorimeter is $726\ \mathrm{kJ\ mol^{-1}}$ at $27^\circ\mathrm{C}$. The enthalpy of combustion for the reaction is $-x\ \mathrm{kJ\ mol^{-1}}$, where $x$ is ________. (Nearest integer) (Given : R=8.3 \mathrm{J}\,$\mathrm{K^{-1}}$\,$\mathrm{mol^{-1}}$)

Answer: 727

Solution

Given $\Delta U = -726 \, \mathrm{KJ/mol}$. $\Delta ng = 1 - 3/2 = -\frac{1}{2}$. $\Delta H = \Delta U + \Delta ng RT$. $$= -726 - \frac{1}{2} \times \frac{8.3 \times 300}{1000}$$ $$= -727.245$$

Question 82

Chemistry · Solutions · Numerical

A 0.5 percent solution of potassium chloride was found to freeze at $-0.24^\circ \mathrm{C}$. The percentage dissociation of potassium chloride is ________. (Nearest integer) (Molal depression constant for water is $1.80 \, \mathrm{K \, kg \, mol^{-1}}$ and molar mass of KCl is $74.6 \, \mathrm{g \, mol^{-1}}$)

Answer: 98

Solution

For a 0.5% solution of KCl, we have: $$\Delta T_f = i \cdot m_f$$ $$0.24 = i \cdot \frac{0.5}{74.6} \times \frac{1.80}{0.1}$$ $$i = \frac{0.24 \times 74.6}{0.5 \times 1.80} \times 0.1$$ $$= 1.989$$ Now, using the equation: $$1.989 = 1 + \alpha (n-1)$$ $$1.989 = 1 + \alpha$$ $$\alpha = 0.989$$ The percentage of $\alpha$ is $98.9\%$. Answer is $99\%$. If the mass of $\mathrm{H_2O} = 99.5$: $$m = \frac{0.5}{74.5} \times \frac{1}{0.0995}$$ $$i = \frac{0.24 \times 74.6 \times 0.0995}{0.5 \times 1.80}$$ $$= 1.979$$ Again, using the equation: $$1.979 = 1 + \alpha (n-1)$$ The percentage of $\alpha$ is $97.9\%$.

Question 83

Chemistry · Equilibrium · Numerical

50 $\mathrm{mL}$ of 0.1$\mathrm{M}$ $CH_3COOH$ is being titrated against 0.1 $\mathrm{M}$ NaOH. When 25 $\mathrm{mL}$ of NaOH has been added, the pH of the solution will be $\times 10^{-2}$. (Nearest integer) (Given : $pK_a (CH_3COOH)$ = 4.76) $\log$ 2 = 0.30

Answer: 476

Solution

Moles of $\mathrm{CH_3COOH} = 5$ m mole. Moles of $\mathrm{NaOH} = 2.5$ m mole. $$\mathrm{NaOH} + \mathrm{CH_3COOH} \longrightarrow \mathrm{CH_3COONa} + \mathrm{H_2O}$$ $2.5$ m mole $2.5$ m mole $0 2.5$ m mole $ 2.5$ m mole So buffer is formed. $$\mathrm{pH} = \mathrm{pKa} + \log \left( \frac{2.5/75}{2.5/75} \right) = \mathrm{pKa}$$ $$\mathrm{pH} = 4.76$$ $$= 476 \times 10^{-2}$$

Question 84

Chemistry · Chemical Kinetics and Nuclear Chemistry · Numerical

A flask is filled with equal moles of A and B. The half lives of A and B are 100 s and 50 s respectively and are independent of the initial concentration. The time required for the concentration of A to be four times that of B is _________ s. (Given : $\ln 2 = 0.693$)

Answer: 200

Solution

Given $k_A = \frac{\ln 2}{100}$ and $k_B = \frac{\ln 2}{50}$. $A_t = A_0 \times e^{-k_A t}$ $A_t = A_0 \times e^{\left(-\frac{\ln 2}{100} \times t\right)}$ $B_t = B_0 \times e^{\left(-\frac{\ln 2}{50} \times t\right)}$ $A_0 = B_0$ And $A_t = 4B_t$ $e^{-\frac{\ln 2}{100} \times t} = 4 \times e^{-\frac{\ln 2}{50} \times t}$ $e^{\frac{\ln 2}{100} \times t} = 4$ $e^{\frac{\ln 2}{100} \times t} = 4$ $\frac{\ln 2}{100} \times t = \ln 4 = 2 \ln 2$ $t = 200 \, sec$

Question 85

Chemistry · Surface Chemistry · Numerical

2.0 g of $\mathrm{H}_2$ gas is adsorbed on 2.5 g of platinum powder at 300 K and 1 bar pressure. The volume of the gas adsorbed per gram of the adsorbent is ________ mL. (Given: R = 0.083 \, $\mathrm{L}$ \, $\mathrm{bar}$ \, $\mathrm{K}^{-1}$ \, $\mathrm{mol}^{-1}$)

Answer: 9960

Solution

Volume of $\mathrm{H_2} = \frac{nRT}{p} = \frac{2}{2} \times \frac{0.083 \times 300}{1}$ $$= 24.92$$ $$= 24900 \, \mathrm{mL}$$ So 'g platinum adsorb $= \frac{24900}{2.5} \, \mathrm{mL} \mathrm{H_2}$ $$= 9960$$

Question 86

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

The spin–only magnetic moment value of the most basic oxide of vanadium among $\mathrm{V_2O_3}$, $\mathrm{V_2O_4}$ and $\mathrm{V_2O_5}$ is ________ B.M. (Nearest Integer)

Answer: 3

Solution

Most basic oxide is $\mathrm{V_2O_3}$. $\mathrm{V^{+3}} \rightarrow [\mathrm{Ar}] \, 3d^2$ $$\mu = \sqrt{2(2+2)} = 2.84 \, \mathrm{BM} \approx 3$$

Question 87

Chemistry · Co-ordination Compounds · Numerical

The spin–only magnetic moment value of an octahedral complex among $CoCl_3.4NH_3$, $NiCl_2.6H_2O$ and $PtCl_4.2HCl$, which upon reaction with excess of $AgNO_3$ gives 2 moles of $AgCl$ is ________ B.M. (Nearest Integer) $\mathrm{CoCl}_3 \cdot 4\mathrm{NH}_3 \rightarrow [\mathrm{Co(NH}_3)_4\mathrm{Cl}_2]\mathrm{Cl}$ $\mathrm{NiCl}_2 \cdot 6\mathrm{H}_2\mathrm{O} \rightarrow [\mathrm{Ni(H}_2\mathrm{O})_6]\mathrm{Cl}_2$ $\mathrm{PtCl}_4 \cdot 2\mathrm{HCl} \rightarrow \mathrm{H}_2[\mathrm{PtCl}_6]$ $[\mathrm{Ni(H}_2\mathrm{O})_6]\mathrm{Cl}_2 \xrightarrow{2\mathrm{AgNO}_3} 2\mathrm{AgCl} \downarrow + [\mathrm{Ni(H}_2\mathrm{O})_6](\mathrm{NO}_3)_2$ $\mu = \sqrt{2(2+2)} \,\mathrm{B.M.}$ $= 2.84 \approx 3$

Answer: 3

Solution

$\mathrm{CoCl_3 \cdot 4NH_3 \rightarrow [Co(NH_3)_4Cl_2]Cl}$ $\mathrm{NiCl_2 \cdot 6H_2O \rightarrow [Ni(H_2O)_6]Cl_2}$ $\mathrm{PtCl_4 \cdot 2HCl \rightarrow H_2[PtCl_6]}$ $\mathrm{[Ni(H_2O)_6]Cl_2 \xrightarrow{2AgNO_3} 2AgCl \downarrow + [Ni(H_2O)_6](NO_3)_2}$ $\mu = \sqrt{2(2+2)}\,\mathrm{B.M.}$ $= 2.84 \approx 3$

Question 88

Chemistry · Some Basic Concepts of Chemistry · Numerical

On complete combustion 0.30 g of an organic compound gave 0.20 g of carbon dioxide and 0.10 g of water. The percentage of carbon in the given organic compound is ______ (Nearest Integer)

Answer: 18

Solution

The reaction is given by: $$\mathrm{C_xH_yO_z} + \left( x + \frac{y}{4} - \frac{z}{2} \right) \mathrm{O_2} \rightarrow x\mathrm{CO_2} + \frac{y}{2} \mathrm{H_2O}$$ Given 0.3 g of $\mathrm{C_xH_yO_z}$ and 0.2 g of $\mathrm{O_2}$ produce 1 g of products. The moles of $\mathrm{CO_2}$ and $\mathrm{H_2O}$ are: $$n_{\mathrm{CO_2}} = \frac{x}{44} = \frac{0.2}{44}$$ $$n_{\mathrm{H_2O}} = \frac{y}{2} = \frac{1}{18}$$ From the equations: $$\frac{2x}{y} = \frac{36}{44} = \frac{9}{11}$$ Solving for $x$: $$x = \frac{9y}{22}$$ The ratio of moles is: $$\frac{n_{\mathrm{C_xH_yO_z}}}{n_{\mathrm{CO_2}}} = \frac{1}{x}$$ Calculating: $$\frac{0.3}{12x + y + 16z} \times \frac{44}{0.2} = \frac{1}{x}$$ Simplifying: $$66x = 12x + y + 16z$$ $$54x = y + 16z$$ Substituting $x$: $$54 \times \frac{9y}{22} = y = 16z$$ Solving for $y$: $$\frac{464y}{22} = 16z$$ Solving for $z$: $$z = \frac{29y}{22}$$ The empirical formula is: $$\mathrm{C_xH_yO_z} = \mathrm{C_xH_yO_z}$$ The molecular formula is: $$\mathrm{C_9H_{22}O_{29}}$$ Calculating the percentage of carbon: $$\% of C = \frac{12 \times 9}{(12 \times 9 + 22 \times 1 + 16 \times 29)} \times 100 = \frac{108}{594} \times 100$$ The percentage of carbon is 18.18%.

Question 89

Chemistry · Amines · Numerical

Compound 'P' on nitration with dil. HNO_3 yields two isomers (A) and (B). These isomers can be separated by steam distillation. Isomers (A) and (B) show the intramolecular and intermolecular hydrogen bonding respectively. Compound (P) on reaction with conc. $HNO_3$ yields a yellow compound 'C', a strong acid. The number of oxygen atoms is present in compound 'C' ________.

Answer: 7

Solution

Question 90

Chemistry · Biomolecules · Numerical

The number of oxygens present in a nucleotide formed from a base, that is present only in RNA is _________.

Answer: 9

Solution

Uracil is the base which only present is RNA. Structure of nucleotides number of 0-9.