JEE Main 29 January 2023 Shift 2 question paper with solutions
JEE Main 29 January 2023 Shift 2: all 90 questions in paper order (Physics, Chemistry, Maths) with the answer key and worked solutions. Free to read; attempt it as a timed 3-hour mock test.
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Physics
Question 1
Physics · Mathematics in Physics · Numerical
In an experiment of measuring the refractive index of a glass slab using travelling microscope in physics lab, a student measures real thickness of the glass slab as 5.25 mm and apparent thickness of the glass slab at 5.00 mm. Travelling microscope has 20 divisions in one cm on main scale and 50 divisions on Vernier scale is equal to 49 divisions on main scale. The estimated uncertainty in the measurement of refractive index of the slab is $\frac{x}{10} \times 10^{-3}$, where $x$ is ________.
Physics · Physical World, Units and Measurements · Single correct
The equation of a circle is given by $x^2 + y^2 = a^2$, where $a$ is the radius. If the equation is modified to change the origin other than $(0, 0)$, then find out the correct dimensions of $A$ and $B$ in a new equation: $(x - At)^2 + \left( y - \frac{t}{B} \right)^2 = a^2$. The dimensions of $t$ is given as $[T^{-1}]$.
$A = [L^{-1} \, T], \ B = [LT^{-1}]$
$A = (LT), \ B = [L^{-1}T^{-1}]$
$A = [L^{-1}T^{-1}], \ B = [LT^{-1}]$
$A = [L^{-1}T^{-1}], \ B = [LT]$
Answer: (b)
Solution
Given $\left( x - At \right)^2 + \left( y - \frac{t}{B} \right)^2 = a^2$. $[At] = A \times \frac{1}{T} = L$. Therefore, $[A] = T^1 L^1$. $\frac{t}{B}$ is in meters. Therefore, $\frac{1}{T[B]} = L$. Thus, $[B] = T^{-1} L^{-1}$. Correct Ans. (2)
Question 3
Physics · Motion in a Plane · Single correct
An object moves at a constant speed along a circular path in a horizontal plane with centre at the origin. When the object is at $x = +2 \, \mathrm{m}$, its velocity is $-4\hat{j} \, \mathrm{m/s}$. The object's velocity $(v)$ and acceleration $(a)$ at $x = -2 \, \mathrm{m}$ will be
The centripetal acceleration is given by $a_c = \frac{v^2}{r}$. Substituting the values, we have $$a_c = \frac{4^2}{2} = \frac{16}{2} = 8 \, \mathrm{m/s^2}.$$ The velocity vector is $\vec{V} = 4\hat{j}$. Therefore, the centripetal acceleration vector is $\vec{a_c} = 8\hat{i}$.
Question 4
Physics · Laws of Motion · Numerical
A car is moving on a circular path of radius 600 m such that the magnitudes of the tangential acceleration and centripetal acceleration are equal. The time taken by the car to complete first quarter of revolution, if it is moving with an initial speed of 54 km/hr is $t(1-e^{-\pi/2})$ s. The value of $t$ is.
Answer: 40
Solution
Given $v \frac{dv}{dx} = \frac{v^2}{R}$, we have $\int_{15}^{v} \frac{dv}{v} = \frac{1}{R} \int_{0}^{x} dx$. This gives $v = 15 e^{x/R}$. Then, $\frac{dx}{dt} = 15 e^{x/R}$. Integrating, we have $$\frac{\pi R}{2} \int_{0}^{0} e^{-x/R} dx = 15 \int_{0}^{t_0} dt$$ which results in $$t_0 = 40 \left(1 - e^{-\pi/2}\right).$$
Question 5
Physics · Motion in a Plane · Numerical
A particle of mass 100 g is projected at time $t = 0$ with a speed $20 \, \mathrm{ms}^{-1}$ at an angle $45^\circ$ to the horizontal as given in the figure. The magnitude of the angular momentum of the particle about the starting point at time $t = 2 \, \mathrm{s}$ is found to be $\sqrt{K} \, \mathrm{kgm}^2 / \mathrm{s}$. The value of $K$ is _______. (Take $g = 10 \, \mathrm{ms}^{-2}$)
The time taken by an object to slide down $45^\circ$ rough inclined plane is $n$ times as it takes to slide down a perfectly smooth $45^\circ$ incline plane. The coefficient of kinetic friction between the object and the incline plane is
$\sqrt{\frac{1}{1-n^2}}$
$\sqrt{1-\frac{1}{n^2}}$
$1+\frac{1}{n^2}$
$1-\frac{1}{n^2}$
Answer: (d)
Solution
Given $a_1 = g \sin \theta = \frac{g}{\sqrt{2}}$. $a_2 = g \sin \theta - K g \cos \theta = \frac{g}{\sqrt{2}} - \frac{K g}{\sqrt{2}}$. $t_2 = n t_1$ and $a_1 t_1^2 = a_2 t_2^2$. $$\frac{g}{\sqrt{2}} t_1^2 = \left( \frac{g}{\sqrt{2}} - \frac{K g}{\sqrt{2}} \right) n^2 t_1^2$$ $K = 1 - \frac{1}{n^2}$. Ans. 4
Question 7
Physics · Laws of Motion · Single correct
Force acts for 20 s on a body of mass 20 kg, starting from rest, after which the force ceases and then body describes 50 m in the next 10 s. The value of force will be :
40 N
5 N
20 N
10 N
Answer: (b)
Solution
Given the problem, we start with the equation for distance: $$50 = V \times 10$$ Solving for $V$, we get $$V = 5 \, \mathrm{m/s}$$ Using the equation for velocity, $$V = 0 + a \times 20$$ Substituting the value of $V$, $$5 = a \times 20$$ Solving for $a$, we find $$a = \frac{1}{4} \, \mathrm{m/s^2}$$ Using Newton's second law, $$F = ma = 20 \times \frac{1}{4} = 5 \, \mathrm{N}$$
Question 8
Physics · Work, Energy and Power · Single correct
Identify the correct statements from the following: (A) Work done by a man in lifting a bucket out of a well by means of a rope tied to the bucket is negative. (B) Work done by gravitational force in lifting a bucket out of a well by a rope tied to the bucket is negative. (C) Work done by friction on a body sliding down an inclined plane is positive. (D) Work done by an applied force on a body moving on a rough horizontal plane with uniform velocity in zero. (E) Work done by the air resistance on an oscillating pendulum in negative. Choose the correct answer from the options given below:
B and E only
A and C only
B, D and E only
B and D only
Answer: (a)
Solution
No Solution Available
Question 9
Physics · Gravitation · Single correct
The time period of a satellite of earth is 24 hours. If the separation between the earth and the satellite is decreased to one fourth of the previous value, then its new time period will become.
Physics · Mechanical Properties of Fluids · Single correct
A fully loaded boeing aircraft has a mass of $5.4 \times 10^5 \, \mathrm{kg}$. Its total wing area is $500 \, \mathrm{m}^2$. It is in level flight with a speed of $1080 \, \mathrm{km/h}$. If the density of air $\rho$ is $1.2 \, \mathrm{kg \, m^{-3}}$, the fractional increase in the speed of the air on the upper surface of the wing relative to the lower surface in percentage will be $(g = 10 \, \mathrm{m/s^2})$
Physics · Mechanical Properties of Fluids · Numerical
A metal block of base area $0.20 \, \mathrm{m}^2$ is placed on a table, as shown in figure. A liquid film of thickness $0.25 \, \mathrm{mm}$ is inserted between the block and the table. The block is pushed by a horizontal force of $0.1 \, \mathrm{N}$ and moves with a constant speed. If the viscosity of the liquid is $5.0 \times 10^{-3} \, \mathrm{Pl}$, the speed of block is _______ $\times 10^{-3} \, \mathrm{m/s}$.
Physics · Thermal Properties of Matter · Single correct
\[ \text{Heat energy of }184\ \text{kJ is given to ice of mass }600\ \text{g} \] \[ \text{at }-12^\circ\text{C}, \text{ Specific heat of ice is } 2222.3\ \text{J kg}^{-1}\,^\circ\text{C}^{-1} \] \[ \text{and latent heat of ice is } 336\ \text{kJ kg}^{-1} \] \[ \text{(A) Final temperature of system will be }0^\circ\text{C.} \] \[ \text{(B) Final temperature of the system will be} \] \[ \text{greater than }0^\circ\text{C.} \] \[ \text{(C) The final system will have a mixture of ice and} \] \[ \text{water in the ratio of }5:1. \] \[ \text{(D) The final system will have a mixture of ice and} \] \[ \text{water in the ratio of }1:5. \] \[ \text{(E) The final system will have water only.} \] \[ \text{Choose the correct answer from the options given} \] \[ \text{below:} \]
A and D only
B and D only
A and E only
A and C only
Answer: (a)
Solution
Given $\Delta Q = 184 \times 10^3$. $m = 0.600 \, \mathrm{kg}$ at $-12^\circ \mathrm{C}$. $S = 222.3 \, \mathrm{J/kg}^\circ \mathrm{C}$. $L = 336 \times 10^3 \, \mathrm{J/kg}$. $Q_1 = 0.600 \times 2222.3 \times 12 = 16000.56 \, \mathrm{J}$. Remaining heat $\Delta Q_1 = 184000 - 16000.56 = 167999.44 \, \mathrm{J}$. For meeting at $0^\circ \mathrm{C}$, $\Delta Q_2 = 0.600 \times 336000 = 201600 \, \mathrm{J}$ needed. Therefore, 100$\%$ ice is not melted. Amount of ice melted: $167999.44 = m \times 336000 = 0.4999 \, \mathrm{kg}$. Therefore, mass of water $= 0.4999 \, \mathrm{kg}$. Mass of ice $= 0.1001$. Therefore, Ratio $= \frac{0.1001}{0.4999} \approx 1 : 5$.
Question 13
Physics · Kinetic Theory · Single correct
At 300 K, the rms speed of oxygen molecules is $\sqrt{\frac{\alpha + 5}{\alpha}}$ times to that of its average speed in the gas. Then, the value of $\alpha$ will be (used $\pi = \frac{22}{7}$)
32
28
24
27
Answer: (b)
Solution
Given the equation $$\sqrt{\frac{3RT}{M}} = \sqrt{\frac{\alpha + 5}{\alpha}} \sqrt{\frac{8}{\pi} \frac{RT}{M}}$$. Simplifying, we have $$3 = \frac{\alpha + 5}{\alpha} \frac{8}{\pi}$$. Solving for $\alpha$, we find $$\alpha = 28$$.
Question 14
Physics · Oscillations · Numerical
A particle of mass 250 \, $\mathrm{g}$ executes a simple harmonic motion under a periodic force $F = (-25 \, x) \, \mathrm{N}$. The particle attains a maximum speed of $4 \, \mathrm{m/s}$ during its oscillation. The amplitude of the motion is \______ $\mathrm{cm}$.
Answer: 40
Solution
Given $\($ $\frac{1}{4}$ a = -25x $\)$, we have $\($ a = -100x $\)$. Since $\($ $\omega$^2 = 100 $\)$, it follows that $\($ $\omega$ = 10 $\)$. Given $\($ $\omega$ A = 4 $\)$, we find $\($ A = $\frac{4}{10}$ = 0.4 \, $\mathrm{m}$ $\)$. Thus, $\($ A = 40 \, $\mathrm{cm}$ $\)$.
Question 15
Physics · Electric Charges and Fields · Single correct
A point charge $2 \times 10^{-2} \, \mathrm{C}$ is moved from $P$ to $S$ in a uniform electric field of $30 \, \mathrm{NC}^{-1}$ directed along positive x-axis. If coordinates of $P$ and $S$ are $(1, 2, 0) \, \mathrm{m}$ and $(0, 0, 0) \, \mathrm{m}$ respectively, the work done by electric field will be
1200 mJ
600 mJ
$-600$ mJ
$-1200$ mJ
Answer: (c)
Solution
The work done by the electric field is given by $\omega_E = q \vec{E} \cdot \vec{S}$. Substituting the given values, we have: $$\omega_E = 2 \times 10^{-2} \left[ 30 \hat{i} \cdot (-\hat{i}) \right]$$ This simplifies to: $$= 2 \times 10^{-2} (-30)$$ Further simplifying: $$= -60 \times 10^{-2}$$ Converting to joules: $$= \frac{-60}{100} = -0.6 \, \mathrm{J}$$ Finally, converting to millijoules: $$= -600 \, \mathrm{mJ}$$
Question 16
Physics · Electric Charges and Fields · Numerical
For a charged spherical ball, electrostatic potential inside the ball varies with $r$ as $V = 2ar^2 + b$. Here, $a$ and $b$ are constant and $r$ is the distance from the center. The volume charge density inside the ball is $-\lambda a \varepsilon$. The value of $\lambda$ is ________. $\varepsilon =$ permittivity of medium.
With the help of potentiometer, we can determine the value of emf of a given cell. The sensitivity of the potentiometer is \begin{enumerate} \item[(A)] directly proportional to the length of the potentiometer wire \item[(B)] directly proportional to the potential gradient of the wire \item[(C)] inversely proportional to the potential gradient of the wire \item[(D)] inversely proportional to the length of the potentiometer wire \end{enumerate} Choose the correct option for the above statements:
B and D only
A and C only
A only
C only
Answer: (b)
Solution
Sensitivity of potentiometer wire is inversely proportional to potential gradient.
Question 18
Physics · Experimental Physics · Numerical
A null point is found at 200 cm in potentiometer when cell in secondary circuit is shunted by $5 \, \Omega$. When a resistance of $15 \, \Omega$ is used for shunting null point moves to 300 cm. The internal resistance of the cell is $\_$$\_$$\_$$\_$ $\Omega$.
Answer: 5
Solution
Given the equation $$\frac{\varepsilon}{r+5} \times 5 = 200x \ldots (1)$$ and $$\frac{\varepsilon \times 15}{r+15} = 300x \ldots (2)$$ solving these equations gives $$\Rightarrow r = 5 \, \Omega$$ Ans. 5
Question 19
Physics · Moving Charges and Magnetism · Single correct
The electric current in a circular coil of four turns produces a magnetic induction 32 T at its centre. The coil is unwound and is rewound into a circular coil of single turn, the magnetic induction at the centre of the coil by the same current will be:
8T
4T
2T
16T
Answer: (c)
Solution
Given $B = \frac{\mu_0 i}{2R} \times 4$. Then $B' = \frac{\mu_0 i}{2R'}$. Given $R' = 4R$, we have $$B' = \frac{\mu_0 i}{8R}$$ Thus, $$\frac{B'}{B} = \frac{1}{16}$$ Finally, $B' = 2T$.
Question 20
Physics · Moving Charges and Magnetism · Single correct
A square loop of area $25 \mathrm{cm}^2$ has a resistance of $10 \Omega$. The loop is placed in uniform magnetic field of magnitude $40.0 \, \mathrm{T}$. The plane of loop is perpendicular to the magnetic field. The work done in pulling the loop out of the magnetic field slowly and uniformly in $1.0 \, \mathrm{sec}$, will be
$2.5 \times 10^{-3} \, \mathrm{J}$
$1.0 \times 10^{-3} \, \mathrm{J}$
$1.0 \times 10^{-4} \, \mathrm{J}$
$5 \times 10^{-3} \, \mathrm{J}$
Answer: (b)
Solution
Given $\ell = 50 \, \mathrm{cm}$ and $t = 1 \, \mathrm{sec}$. Therefore, $$V = \frac{0.05}{1} = 0.05 \, \mathrm{m/s}.$$ The current $i$ is given by $$i = \frac{40 \times 0.05 \times 0.05}{10} = 0.01 \, \mathrm{A}.$$ The force $F$ is calculated as $$F = B i \ell = 40 \times 0.01 \times 0.05.$$ Thus, $$F = 0.02 \, \mathrm{N}.$$ Therefore, the work $W$ is $$W = 0.02 \times \ell = 0.02 \times 0.05.$$ Finally, $$W = 1 \times 10^{-3} \, \mathrm{J}.$$
Question 21
Physics · Alternating Current · Multiple correct
For the given figures, choose the correct options:
The rms current in circuit (b) can never be larger than that in (a)
The rms current in figure (a) is always equal to that in figure (b)
The rms current in circuit (b) can be larger than that in (a)
At resonance, current in (b) is less than that in (a)
Answer: (a)
Solution
Given a circuit with a resistance of $40 \, \Omega$ and a voltage of $220 \, \mathrm{V}$ at $50 \, \mathrm{Hz}$, the rms current $I_{\mathrm{rms}}$ is calculated as follows: $$I_{\mathrm{rms}} = \frac{220}{40} = 5.5 \, \mathrm{A}$$ In the second circuit, with a resistance of $40 \, \Omega$, an inductance of $50 \, \mathrm{mH}$, and a capacitance of $0.5 \, \mu\mathrm{F}$, $X_L$ is not equal to $X_C$. So rms current in (b) can never be larger than (a).
Question 22
Physics · Alternating Current · Numerical
An inductor of inductance 2 $\mu$$\mathrm{H}$ is connected in series with a resistance, a variable capacitor and an AC source of frequency 7 $\mathrm{kHz}$. The value of capacitance for which maximum current is drawn into the circuit is $\frac{1}{x}$ $\mathrm{F}$, where the value of x is _____. (Take $\pi=\frac{22}{7}$)
Answer: 3872
Solution
Given $\frac{1}{2\pi f C}=2\pi f L$. $C=\frac{1}{4\pi^2f^2L}=\frac{1}{4\times\pi^2\times49\times10^6\times2\times10^{-6}}$ $C=\frac{1}{3872}\,\mathrm{F}$ $x=3872$
Question 23
Physics · Electromagnetic Waves · Single correct
Given below are two statements: Statement I : Electromagnetic waves are not deflected by electric and magnetic field. Statement II : The amplitude of electric field and the magnetic field in electromagnetic waves are related to each other as $E_0 = \sqrt{\frac{\mu_0}{\varepsilon_0}} B_0$ In the light of the above statements, choose the correct answer from the options given below:
Statement I is true but statement II is false
Both Statement I and Statement II are true
Statement I is false but statement II is true
Both Statement I and Statement II are false
Answer: (a)
Solution
Statement-I is correct as EMW are neutral. Statement-II is wrong. $$E_0 = \sqrt{\frac{1}{\mu_0 \varepsilon_0}} B_0$$
Question 24
Physics · Ray Optics and Optical Instruments · Single correct
A scientist is observing a bacteria through a compound microscope. For better analysis and to improve its resolving power he should. (Select the best option)
Increase the wave length of the light
Increase the refractive index of the medium between the object and objective lens
Decrease the focal length of the eye piece
Decrease the diameter of the objective lens
Answer: (a)
Solution
The formula for P is given by $$P = \frac{2 \mu \sin \theta}{1.22 \lambda}.$$
Question 25
Physics · Wave Optics · Numerical
Unpolarised light is incident on the boundary between two dielectric media, whose dielectric constants are 2.8 (medium –1) and 6.8 (medium –2), respectively. To satisfy the condition, so that the reflected and refracted rays are perpendicular to each other, the angle of incidence should be $\tan^{-1}\left(1 + \frac{10}{\theta}\right)^{\frac{1}{2}}$ the value of $\theta$ is _____. (Given for dielectric media, $\mu_r = 1$)
Answer: 7
Solution
Given $\mu_1 = \sqrt{2.8 \times 1} = \sqrt{2.8}$. $\mu_2 = \sqrt{6.8 \times 1} = \sqrt{6.8}$. $\mu_1 \sin i = \mu_2 \cos i$ $\tan i = \frac{\mu_2}{\mu_1} = \sqrt{\frac{6.8}{2.8}}$ $\tan i = \left( \frac{2.8 + 4}{2.8} \right)^{1/2}$ $i = \tan^{-1} \left( 1 + \frac{10}{7} \right)^{1/2}$ $\theta = 7$ Ans.
Question 26
Physics · Dual Nature of Radiation and Matter · Single correct
The ratio of de-Broglie wavelength of an $\alpha$-particle and a proton accelerated from rest by the same potential is $\frac{1}{\sqrt{m}}$, the value of $m$ is
4
16
8
2
Answer: (c)
Solution
Given $\($ $\frac{\lambda_\alpha}{\lambda_p}$ = $\frac{\frac{h}{\sqrt{2m_\alpha q_\alpha V}}}{\frac{h}{\sqrt{2m_p q_p V}}}$ $\)$. This simplifies to $\($ $\frac{\lambda_\alpha}{\lambda_p}$ = $\sqrt{\frac{1}{8}}$ $\)$ when $\($ m = 8 $\)$. Ans. 3
Question 27
Physics · Nuclei · Single correct
Substance A has atomic mass number 16 and half life of 1 day. Another substance B has atomic mass number 32 and half life of $\frac{1}{2}$ day. If both A and B simultaneously start undergo radio activity at the same time with initial mass 320 g each, how many total atoms of A and B combined would be left after 2 days.
Physics · Semiconductor Electronics: Materials, Devices and Simple Circuits · Single correct
For the given logic gates combination, the correct truth table will be
Answer: (b)
Solution
Question 29
Physics · Communication Systems · Single correct
The modulation index for an A.M. wave having maximum and minimum peak to peak voltages of 14 $\mathrm{mV}$ and 6 $\mathrm{mV}$ respectively is:
1.4
0.4
0.2
0.6
Answer: (b)
Solution
The modulation index $\mu$ is given by the formula: $$\mu = \frac{A_{max} - A_{min}}{A_{max} + A_{min}}.$$ Substituting the given values: $$\mu = \frac{14 - 6}{14 + 6} = 0.4.$$
Question 30
Physics · Current Electricity · Numerical
When two resistance $R_1$ and $R_2$ connected in series and introduced into the left gap of a meter bridge and a resistance of $10 \, \Omega$ is introduced into the right gap, a null point is found at $60 \, \mathrm{cm}$ from left side. When $R_1$ and $R_2$ are connected in parallel and introduced into the left gap, a resistance of $3 \, \Omega$ is introduced into the right-gap to get null point at $40 \, \mathrm{cm}$ from left end. The product of $R_1 \, R_2$ is _____ $\Omega^2$
Assume that the radius of the first Bohr orbit of hydrogen atom is 0.6 Å. The radius of the third Bohr orbit of He$^+$ is _______ picometer. (Nearest Integer)
Answer: 270
Solution
The radius $r$ is proportional to $\frac{n^2}{Z}$. $$r_{\mathrm{He}^+} = r_{\mathrm{H}} \times \frac{n^2}{Z}$$ Substituting the values, $$r_{\mathrm{He}^+} = 0.6 \times \frac{(3)^2}{2}$$ $$= 2.7 \, \mathrm{\AA}$$ Therefore, $$r_{\mathrm{He}^+} = 270 \, \mathrm{pm}$$
Question 32
Chemistry · The p-Block Elements (Group-13 and 14) · Single correct
Given below are two statements: Statement I : The decrease in first ionization enthalpy from B to Al is much larger than that from Al to Ga. Statement II : The d orbitals in Ga are completely filled. In the light of the above statements, choose the most appropriate answer from the options given below
Statement I is incorrect but statement II is correct.
Both the statements I and II are correct
Statement I is correct but statement II is incorrect
Both the statements I and II are incorrect
Answer: (b)
Solution
The first ionization energies (as in NCERT) are as follows: B: $801 \, \mathrm{kJ/mol}$ Al: $577 \, \mathrm{kJ/mol}$ Ga: $579 \, \mathrm{kJ/mol}$ Ga: $[\mathrm{Ar}]3d^{10}4s^24p^1$
Question 33
Chemistry · Chemical Bonding and Molecular Structure · Single correct
According to MO theory the bond orders for $\mathrm{O}_2^{2-}$, CO and $\mathrm{NO}^+$ respectively, are
1, 3 and 3
1, 3 and 2
1, 2 and 3
2, 3 and 3
Answer: (a)
Solution
Theory based.
Question 34
Chemistry · Thermodynamics · Single correct
Which of the following relations are correct? A. $\Delta U = q + p \Delta V$ B. $\Delta G = \Delta H - T \Delta S$ C. $\Delta S = \frac{q_{rev}}{T}$ D. $\Delta H = \Delta U - \Delta nRT$ Choose the most appropriate answer from the options given below:
C and D only
B and C only
A and B only
B and D only
Answer: (b)
Solution
Only (B) and (C) are correct. (B) $G = H - TS$ At constant $T$ $\Delta G = \Delta H - T\Delta S$ (A) First law is given by $\Delta U = Q + W$ If we apply constant $P$ and reversible work, $\Delta U = Q - P\Delta V$ (C) By definition of entropy change $dS = \dfrac{dq_{\mathrm{rev}}}{T}$ At constant $T$ $\Delta S = \dfrac{q_{\mathrm{rev}}}{T}$ (D) $H = U + PV$ For ideal gas $H = U + nRT$ At constant $T$ $\Delta H = \Delta U + \Delta(nRT)$ $\Delta H = \Delta U + nR\Delta T$ Since $\Delta T = 0$ at constant $T$ $\Delta H = \Delta U$ Choose the most appropriate answer from the options given below:
Question 35
Chemistry · Equilibrium · Numerical
At 298 K $\mathrm{N_2(g) + 3H_2(g) \rightleftharpoons 2NH_3(g)}, \ K_1 = 4 \times 10^5$ $\mathrm{N_2(g) + O_2(g) \rightleftharpoons 2NO(g)}, \ K_2 = 1.6 \times 10^{12}$ $\mathrm{H_2(g) + \frac{1}{2}O_2(g) \rightleftharpoons H_2O(g)}, \ K_3 = 1.0 \times 10^{-13}$ Based on above equilibria, the equilibrium constant of the reaction, $\mathrm{2NH_3(g) + \frac{5}{2}O_2(g) \rightleftharpoons 2NO(g) + 3H_2O(g)}$ is ___ $\times 10^{-33}$ (Nearest integer)
Chemistry · Some Basic Concepts of Chemistry · Numerical
The volume of HCl, containing 73 $\mathrm{g \, L^{-1}}$, required to completely neutralise NaOH obtained by reacting 0.69 $\mathrm{g}$ of metallic sodium with water, is _______ $\mathrm{mL}$. (Nearest Integer) (Given : molar Masses of Na, Cl, O, H are 23, 35.5, 16 and 1 $\mathrm{g \, mol^{-1}}$ respectively)
Answer: 15
Solution
Mole of Na $=\dfrac{0.69}{23}=3\times10^{-2}$ $\mathrm{Na + H_2O \rightarrow NaOH + \dfrac{1}{2}H_2}$ By using POAC Moles of NaOH $=3\times10^{-2}$ NaOH reacts with HCl No. of equivalent of NaOH $=$ No. of equivalent of HCl $3\times10^{-2}\times1=\dfrac{73}{36.5}\times V\text{(in L)}\times1$ $V=1.5\times10^{-2}\ \mathrm{L}$ Volume of HCl $=15\ \mathrm{mL}$
Question 37
Chemistry · Redox Reactions · Single correct
An indicator 'X' is used for studying the effect of variation in concentration of iodide on the rate of reaction of iodide ion with $\mathrm{H_2O_2}$ at room temp. The indicator 'X' forms blue colored complex with compound 'A' present in the solution. The indicator 'X' and compound 'A' respectively are
Starch and iodine
Methyl orange and $\mathrm{H_2O_2}$
Starch and $\mathrm{H_2O_2}$
Methyl orange and iodine
Answer: (a)
Solution
The reaction is given by: $$\mathrm{I^- + H_2O_2 \rightarrow I_2 (\mathrm{A}) + H_2O} $$ Then, $\mathrm{I_2}$ reacts with starch as an indicator to form a blue color: $$\mathrm{I_2 + Starch (\mathrm{Indicator}) \rightarrow Blue}$$
Question 38
Chemistry · The s-Block Elements · Numerical
On heating, $\mathrm{LiNO_3}$ gives how many compounds among the following? $\mathrm{Li_2O}$, $\mathrm{N_2}$, $\mathrm{O_2}$, $\mathrm{LiNO_2}$, $\mathrm{NO_2}$
Answer: 3
Solution
The reaction is given by: $$2 \mathrm{LiNO_3} \xrightarrow{\Delta} \mathrm{Li_2O} + 2\mathrm{NO_2} + \frac{1}{2} \mathrm{O_2}$$ Hence three products $\mathrm{Li_2O}$, $\mathrm{NO_2}$, and $\mathrm{O_2}$.
Question 39
Chemistry · Hydrogen · Single correct
Given below are two statements: Statement I : Nickel is being used as the catalyst for producing syn gas and edible fats. Statement II : Silicon forms both electron rich and electron deficient hydrides. In the light of the above statements, choose the most appropriate answer from the options given below:
Both the statements I and II are correct
Statement I is incorrect but statement II is correct
Both the statements I and II are incorrect
Statement I is correct but statement II is incorrect
Answer: (d)
Solution
Statement–I is correct. Ni is used in Hydrogenation of unsaturated fat to make edible fats. Statement–II is false as hydride of Silicon is electron precise and neither electron deficient nor electron rich.
Question 40
Chemistry · Some Basic Concepts of Chemistry · Single correct
When a hydrocarbon A undergoes combustion in the presence of air, it requires 9.5 equivalents of oxygen and produces 3 equivalents of water. What is the molecular formula of A?
C_8H_6
C_9H_9
C_6H_6
C_9H_6
Answer: (a)
Solution
The balanced chemical equation is: $$\mathrm{C_xH_y} + \left( x + \frac{y}{4} \right) \mathrm{O_2} \rightarrow x \mathrm{CO_2} + \frac{y}{2} \mathrm{H_2O}$$ Solving the equations: $$x + \frac{y}{4} = 9.5$$ $$\frac{y}{2} = 3$$ Thus, $x = 8$ and $y = 6$.
Question 41
Chemistry · Some Basic Concepts of Chemistry · Numerical
When $0.01 \, \mathrm{mol}$ of an organic compound containing $60\%$ carbon was burnt completely, $4.4 \, \mathrm{g}$ of $\mathrm{CO}_2$ was produced. The molar mass of compound is _______ $\mathrm{g \, mol^{-1}}$ (Nearest integer)
Answer: 200
Solution
Let $M$ be the molar mass of the compound (g/mol). The mass of the compound is $0.01 \, M \, \mathrm{gm}$. The mass of carbon is $0.01 \, M \times \frac{60}{100}$. The moles of carbon are given by: $$\frac{0.01 \, M}{12} \times \frac{60}{100}$$ The moles of $\mathrm{CO_2}$ from combustion are: $$\frac{4.4}{44} = moles of carbon$$ Equating the moles of carbon: $$\frac{0.01 \, M}{12} \times \frac{60}{100} = \frac{4.4}{44}$$ Solving for $M$: $$M = \frac{4.4}{44} \times \frac{100}{60} \times \frac{12}{0.01} = 200 \, \mathrm{gm/mol}$$
Question 42
Chemistry · Environmental Chemistry · Single correct
The concentration of dissolved Oxygen in water for growth of fish should be more than $X$ ppm and Biochemical Oxygen Demand in clean water should be less than $Y$ ppm. $X$ and $Y$ in ppm are, respectively.
X Y 6 5
X Y 4 8
X Y 4 15
X Y 6 12
Answer: (a)
Solution
The growth of fish gets inhibited if the concentration of dissolved Oxygen in water is less than 6 ppm and Biochemical Oxygen demand in clean water should be less than 5 ppm.
Question 43
Chemistry · The Solid State · Numerical
A metal M forms hexagonal close-packed structure. The total number of voids in 0.02 mol of it is _______ $\times 10^{21}$ (Nearest integer) (Given $N_A = 6.02 \times 10^{23}$)
Answer: 36
Solution
One unit cell of hcp contains 18 voids. No. of voids in 0.02 mol of hcp $$= \frac{18}{6} \times 6.02 \times 10^{23} \times 0.02$$ $$\approx 3.6 \times 10^{22}$$ $$\approx 36 \times 10^{21}$$
Question 44
Chemistry · Co-ordination Compounds · Single correct
Match List I with List II. Choose the correct answer from the options given below:
A-III, B-I, C-II, D-IV
A-III, B-II, C-I, D-IV
A-III, B-I, C-IV, D-II
A-I, B-III, C-II, D-IV
Answer: (a)
Solution
$(A)$ van't Hoff factor, $i$ $$i = \frac{\text{Normal molar mass}}{\text{Abnormal molar mass}}$$ $(B)$ $k_f =$ Cryoscopic constant $(C)$ Solutions with same osmotic pressure are known as isotonic solutions. $(D)$ Solutions with same composition of vapour over them are called Azeotrope.
Question 45
Chemistry · Electrochemistry · Numerical
The equilibrium constant for the reaction $Zn(s)+Sn^{2+}(aq)\rightleftharpoons Zn^{2+}(aq)+Sn(s)$ is $1\times10^{20}$ at $298\ K$. The magnitude of standard electrode potential of $Sn/Sn^{2+}$ if $E^\circ_{Zn^{2+}/Zn}=-0.76\ V$ is $\underline{\hspace{1cm}}\times10^{-2}\ V$ (Nearest integer) Given $\dfrac{2.303RT}{F}=0.059\ V$
Chemistry · Chemical Kinetics and Nuclear Chemistry · Fill in the blank
For conversion of compound $A \rightarrow B$, the rate constant of the reaction was found to be $4.6 \times 10^{-5} \, \mathrm{L \, mol^{-1} \, s^{-1}}$. The order of the reaction is ______.
Answer: 2
Solution
As unit of rate constant is $(conc.)^{1-n} time^{-1}$ $$\Rightarrow (\mathrm{L\ mol^{-1}}) \Rightarrow 1-n = -1$$ $$n = 2$$
Question 47
Chemistry · Solutions · Single correct
Match List-I and List-II. Match List-I with List-II \begin{tabular}{|l|l|} \hline \textbf{List-I} & \textbf{List-II} \\ & \\ \hline A. Osmosis & I. Solvent molecules pass through \\ & semi-permeable membrane towards \\ & solvent side. \\ \hline B. Reverse osmosis & II. Movement of charged colloidal \\ & particles under the influence of \\ & applied electric potential towards \\ & oppositely charged electrodes. \\ \hline C. Electro osmosis & III. Solvent molecules pass through \\ & semi-permeable membrane towards \\ & solution side. \\ \hline D. Electrophoresis & IV. Dispersion medium moves \\ & in an electric field. \\ \hline \end{tabular} Choose the correct answer from the options given below:
A-I, B-III, C-IV, D-II
A-III, B-I, C-IV, D-II
A-III, B-I, C-II, D-IV
A-I, B-III, C-II, D-IV
Answer: (b)
Solution
A. Osmosis III B. Reverse osmosis I C. Electro osmosis IV D. Electrophoresis II
Question 48
Chemistry · General Principles and Processes of Isolation of Elements · Single correct
The major component of which of the following ore is sulphide based mineral?
Chemistry · The p-Block Elements (Group 15, 16, 17 & 18) · Numerical
Total number of acidic oxides among $\mathrm{N_2O_3}$, $\mathrm{NO_2}$, $\mathrm{N_2O}$, $\mathrm{Cl_2O_7}$, $\mathrm{SO_2}$, $\mathrm{CO}$, $\mathrm{CaO}$, $\mathrm{Na_2O}$ and $\mathrm{NO}$ is .
Answer: 4
Solution
Acidic oxides are $\mathrm{N_2O_3}$, $\mathrm{NO_2}$, $\mathrm{Cl_2O_7}$, $\mathrm{SO_2}$.
Question 50
Chemistry · The d-and f-Block Elements · Single correct
A solution of $\mathrm{CrO_5}$ in amyl alcohol has a....colour
Green
Orange–Red
Yellow
Blue
Answer: (d)
Solution
A solution of $\mathrm{CrO_5}$ in amyl alcohol has a blue colour. So, option (4) is correct.
Question 51
Chemistry · The d-and f-Block Elements · Single correct
The set of correct statements is: (i) Manganese exhibits +7 oxidation state in its oxide. (ii) Ruthenium and Osmium exhibit +8 oxidation in their oxides. (iii) Sc shows +4 oxidation state which is oxidizing in nature. (iv) Cr shows oxidising nature in +6 oxidation state.
(ii) and (iii)
, (ii) and (iv)
and (iii)
(ii), (iii) and (iv)
Answer: (b)
Solution
(i), (ii) and (iv) correct. Manganese exhibits $+7$ oxidation state in its oxide ($\mathrm{Mn_2O_7}$). Ru and Os from $\mathrm{RuO_4}$ and $\mathrm{OsO_4}$ oxide in $+8$ oxidation state. Cr in $+6$ oxidation act is oxidizing. Sc does not show $+4$ oxidation state.
Question 52
Chemistry · Co-ordination Compounds · Single correct
Correct order of spin only magnetic moment of the following complex ions is: (Given At. No. Fe: 26, Co: 27)
For $[\mathrm{FeF}_6]^{3-}$: $\mathrm{Fe}^{3+} = 3d^5$, $\Delta_o P$. Number of unpaired $e^- = 0$. Therefore, $\mu = 0 \, \mathrm{BM}$.
Question 53
Chemistry · Co-ordination Compounds · Fill in the blank
The denticity of the ligand present in the Fehling's reagent is _______.
Answer: 4
Solution
Copper tartarate complex. Denticity = 2
Question 54
Chemistry · Hydrocarbons · Single correct
The one giving maximum number of isomeric alkenes on dehydrohalogenation reaction is (excluding rearrangement)
1-Bromo-2-methylbutane
2-Bromopropane
2-Bromopentane
2-Bromo-3,3-dimethylpentane
Answer: (c)
Solution
The reaction starts with $\mathrm{CH_3 - CH_2 - CH(CH_3) - CH_2 - Br}$ which undergoes a reaction to form $\mathrm{C - C - C = C}$ with a $\mathrm{CH_3}$ group attached. This is labeled as (1). Next, $\mathrm{CH_3 - CH - CH_3}$ with a $\mathrm{Br}$ group undergoes a reaction to form $\mathrm{CH_3CH=CH_2}$, also labeled as (1). Then, $\mathrm{CH_3 - CH_2 - CH_2 - CH(CH_3) - CH_3}$ with a $\mathrm{Br}$ group reacts to form $\mathrm{C - C - C - C - C = C}$ and $\mathrm{C - C - C = C - C}$, with cis and trans isomers, labeled as (3). Finally, $\mathrm{C - C - C - C - C}$ with a $\mathrm{CH_3}$ and $\mathrm{Br}$ group reacts to form $\mathrm{C - C - C - C = C}$ with a $\mathrm{C}$ group attached, labeled as (1).
Question 55
Chemistry · Hydrocarbons · Single correct
Find out the major product for the following reaction.
Answer: (b)
Solution
Question 56
Chemistry · Aldehydes, Ketones and Carboxylic Acids · Single correct
Find out the major products from the following reaction sequence.
Answer: (b)
Solution
The reaction starts with the compound reacting with $NaCN$ to form a cyanohydrin. This intermediate is then treated with $EtOH, H_3O^+$ to form an ester. The ester undergoes a reaction with $MeMgBr$ to form a tertiary alcohol. Further reaction with $MeMgBr$ leads to the formation of a diol.
Question 57
Chemistry · Amines · Single correct
Reaction of propanamide with $\mathrm{Br_2} / \mathrm{KOH} \,(aq)$ produces:
Ethylnitrile
Propylamine
Propanenitrile
Ethylamine
Answer: (d)
Solution
The reaction shown is the Hoffmann Bromamide reaction. It involves the conversion of an amide to an amine with one less carbon atom. The given amide is converted to ethylamine using $\mathrm{Br_2/KOH}$. This reaction results in the removal of the carbonyl group and the formation of an amine.
Question 58
Chemistry · Analytical Chemistry · Single correct
Match List-I and List-II. Choose the correct answer from the options given below:
Chemistry · Chemistry in Everyday Life · Single correct
A doctor prescribed the drug Equanil to a patient. The patient was likely to have symptoms of which disease?
Stomach ulcers
Hyperacidity
Anxiety and stress
Depression and hypertension
Answer: (d)
Solution
Theory based.
Question 60
Chemistry · Biomolecules · Single correct
Following tetrapeptide can be represented as (F, L, D, Y, I, Q, P are one letter codes for amino acids)
FIQY
FLDY
YQLF
PLDY
Answer: (b)
Solution
Hydrolysis of the given tetrapeptide will give the following: Phenylalanine (F), Leucine (L), Aspartic acid (D), Tyrosine (Y).
Maths
Question 61
Maths · Applications of Derivatives · Fill in the blank
Let $\alpha_1$, $\alpha_2$, $\ldots$, $\alpha_7$ be the roots of the equation $x^7 + 3x^5 - 13x^3 - 15x = 0$ and $|\alpha_1| \geq |\alpha_2| \geq \ldots \geq |\alpha_7|$. Then $\alpha_1 \alpha_2 - \alpha_3 \alpha_4 + \alpha_5 \alpha_6$ is equal to _____.
Answer: 9
Solution
Then $\alpha_1 \alpha_2 - \alpha_3 \alpha_4 + \alpha_5 \alpha_6$ is equal to ______. Given equation can be rearranged as $$x(x^6 + 3x^4 - 13x^2 - 15) = 0$$ clearly $x = 0$ is one of the root and other part can be observed by replacing $x^2 = t$ from which we have $$t^3 + 3t^2 - 13t - 15 = 0$$ $$\Rightarrow (t - 3)(t^2 + 6t + 5) = 0$$ So, $t = 3$, $t = -1$, $t = -5$. Now we are getting $x^2 = 3$, $x^2 = -1$, $x^2 = -5$. $$\Rightarrow x = \pm \sqrt{3}, x = \pm i, x = \pm \sqrt{5}i$$ From the given condition $|\alpha_1| \geq |\alpha_2| \geq \ldots \geq |\alpha_7|$ We can clearly say that $|\alpha_7| = 0$ and $|\alpha_6| = \sqrt{5} = |\alpha_5|$ $|\alpha_4| = \sqrt{3} = |\alpha_3|$ and $|\alpha_2| = 1 = |\alpha_1|$ So we can have, $\alpha_1 = \sqrt{5}i$, $\alpha_2 = -\sqrt{5}i$, $\alpha_3 = \sqrt{3}i$, $\alpha_4 = -\sqrt{3}$, $\alpha_5 = i$, $\alpha_6 = -i$. Hence $$\alpha_1 \alpha_2 - \alpha_3 \alpha_4 + \alpha_5 \alpha_6$$ $$= 1 - (-3) + 5 = 9$$
Question 62
Maths · Complex Numbers and Quadratic Equations · Numerical
Let $\alpha=8-14i$, \[ A=\left\{ z\in\mathbb{C}: \frac{\alpha z-\overline{\alpha}\,\overline{z}} {z^2-(\overline{z})^2-112i} =1 \right\} \] and \[ B=\left\{ z\in\mathbb{C}: |z+3i|=4 \right\}. \] Then \[ \sum_{z\in A\cap B}\left(\operatorname{Re}z-\operatorname{Im}z\right) \] is equal to
Answer: 14
Solution
Given $\alpha = 8 - 14i$ and $z = x + iy$. Then, $$az = (8x + 14y) + i(-14x + 8y)$$ $$z + \bar{z} = 2x z - \bar{z} = 2iy$$ Set A: $$\frac{2i(-14x + 8y)}{i(4xy - 112)} = 1$$ $$(x - 4)(y + 7) = 0$$ $$x = 4 or y = -7$$ Set B: $$x^2 + (y + 3)^2 = 16$$ When $x = 4$, $y = -3$ When $y = -7$, $x = 0$ Therefore, $A \cap B = \{4 - 3i, 0 - 7i\}$ So, $$\sum_{z \in A \cap B} (Rez - Imz) = 4 - (-3) + (0 - (-7)) = 14$$
Question 63
Maths · Permutations and Combinations · Single correct
The letters of the word OUGHT are written in all possible ways and these words are arranged as in a dictionary, in a series. Then the serial number of the word TOUGH is :
89
84
86
79
Answer: (a)
Solution
Let's arrange the letters of OUGHT in alphabetical order. G, H, O, T, U Words starting with G$\_$$\_$$\_$$\_$ $\rightarrow$ 4! H$\_$$\_$$\_$$\_$ $\rightarrow$ 4! O$\_$$\_$$\_$$\_$ $\rightarrow$ 4! TG$\_$$\_$$\_$ $\rightarrow$ 3! TH$\_$$\_$$\_$ $\rightarrow$ 3! TOG$\_$$\_$ $\rightarrow$ 2! TOH$\_$$\_$ $\rightarrow$ 2! TOUGH $\rightarrow$ 1! Total = 89
Question 64
Maths · Permutations and Combinations · Numerical
The total number of 4-digit numbers whose greatest common divisor with 54 is 2, is _____.
Answer: 3000
Solution
N should be divisible by 2 but not by 3. N = (Numbers divisible by 2) - (Numbers divisible by 6) $$N = \frac{9000}{2} - \frac{9000}{6} = 4500 - 1500 = 3000$$
Question 65
Maths · Sequences and Series · Numerical
Let $a_1 = b_1 = 1$ and $a_n = a_{n-1} + (n-1)$, $b_n = b_{n-1} + a_{n-1}$, $\forall \, n \geq 2$. If $S = \sum_{n=1}^{10} \frac{b_n}{2^n}$ and $T = \sum_{n=1}^{8} \frac{n}{2^{n-1}}$, then $2^7(2S - T)$ is equal to .
Let $\{a_k\}$ and $\{b_k\}$, $k \in \mathbb{N}$, be two G.P.s with common ratio $r_1$ and $r_2$ respectively such that $a_1 = b_1 = 4$ and $r_1 < r_2$. Let $c_k = a_k + b_k$, $k \in \mathbb{N}$. If $c_2 = 5$ and $c_3 = \frac{13}{4}$ then $$\sum_{k=1}^{\infty} c_k - (12a_6 + 8b_4)$$ is equal to _______.
Maths · Permutations and Combinations · Single correct
The number of 3 digit numbers, that are divisible by either 3 or 4 but not divisible by 48, is
472
432
507
400
Answer: (b)
Solution
Total 3 digit number = 900 Divisible by 3 = 300 (Using $\frac{900}{3} = 300$) Divisible by 4 = 225 (Using $\frac{900}{4} = 225$) Divisible by 3 $\&$ 4 = 108, .... (Using $\frac{900}{12} = 75$) Number divisible by either 3 or 4 = 300 + 225 - 75 = 450 We have to remove divisible by 48, 144, 192, ....., 18 terms Required number of numbers = 450 - 18 = 432
Question 68
Maths · Binomial Theorem · Single correct
Let K be the sum of the coefficients of the odd powers of x in the expansion of $(1+x)^{99}$. Let a be the middle term in the expansion of $$\left(2+\frac{1}{\sqrt{2}}\right)^{200}$$. If $$\frac{{^{200}C_{99}K}}{a} = \frac{2^\ell m}{n}$$, where m and n are odd numbers, then the ordered pair $(\ell, n)$ is equal to:
(50, 51)
(51, 99)
(50, 101)
(51, 101)
Answer: (c)
Solution
In the expansion of $(1+x)^{99}$ $=C_{0}+C_{1}x+C_{2}x^{2}+\cdots+C_{99}x^{99}$ $K=C_{1}+C_{3}+\cdots+C_{99}$ $=2^{98}$ Let $a=$ middle term in the expansion of $\left(2+\frac{1}{\sqrt{2}}\right)^{200}$ $T_{200/2+1}$ $={}^{200}C_{100}(2)^{100}\left(\frac{1}{\sqrt{2}}\right)^{100}$ $={}^{200}C_{100}2^{50}$ So, $\frac{{}^{200}C_{99}\times2^{98}}{{}^{200}C_{100}\times2^{50}}$ $=\frac{100\times2^{48}}{101}$ So,$\frac{25}{m}\times2^{50}=\frac{n}{2^{k}}$ $\therefore$ $m,n$ are odd. $(\ell,n)$ become $(50,101)$.
Question 69
Maths · Trigonometric Functions · Single correct
The set of all values of $\lambda$ for which the equation $$\cos^2 2x - 2\sin^4 x - 2\cos^2 x = \lambda$$
[-2, -1]
[-2, -$\frac{3}{2}$]
[-1, -$\frac{1}{2}$]
[$\frac{3}{2}$, -1]
Answer: (d)
Solution
Given $\lambda = \cos^2 x - 2 \sin^4 x - 2 \cos^2 x$. Convert all in to $\cos x$. $$\lambda = (2 \cos^2 x - 1)^2 - 2(1 - \cos^2 x)^2 - 2 \cos^2 x$$ $$= 4 \cos^4 x - 4 \cos^2 x + 1 - 2(1 - 2 \cos^2 x + \cos^4 x) - 2 \cos^2 x$$ $$= 2 \cos^4 x - 2 \cos^2 x + 1 - 2$$ $$= 2 \cos^4 x - 2 \cos^2 x - 1$$ $$= 2 \left[ \cos^4 x - \cos^2 x - \frac{1}{2} \right]$$ $$= 2 \left[ \left( \cos^2 x - \frac{1}{2} \right)^2 - \frac{3}{4} \right]$$ $$\lambda_{\max} = 2 \left[ \frac{1}{4} - \frac{3}{4} \right] = 2 \times \left( -\frac{2}{4} \right) = -1 (max Value)$$ $$\lambda_{\min} = 2 \left[ 0 - \frac{3}{4} \right] = -\frac{3}{2} (Minimum Value)$$ So, Range = $\left$[ -$\frac{3}{2}$, -1 $\right$].
Question 70
Maths · Conic Sections · Numerical
A circle with centre $(2, 3)$ and radius $4$ intersects the line $x + y = 3$ at the points $P$ and $Q$. If the tangents at $P$ and $Q$ intersect at the point $S(\alpha, \beta)$, then $4\alpha - 7\beta$ is equal to .
Answer: 11
Solution
The given line is polar or $P(2, \beta)$ with respect to the given circle $$x^2 + y^2 - 4x - 6y - 3 = 0$$ Chord or contact $$\alpha x + \beta y - 2(x + \alpha) - 3(y + \beta) - 3 = 0$$ $$\Rightarrow (\alpha - 2)x + (\beta - 3)y - (2\alpha + 3\beta + 3) = 0 \ldots (i)$$ But the equation of chord of contact is given as $$x + y - 3 = 0 \ldots (ii)$$ Comparing the coefficients $$\frac{\alpha - 2}{1} = \frac{\beta - 3}{1} = -\left(\frac{2\alpha + 3\beta + 3}{-3}\right)$$ On solving $\alpha = -6$ $\beta = -5$ Now $$4\alpha - 7\beta = 11$$
Question 71
Maths · Conic Sections · Fill in the blank
A triangle is formed by the tangents at the point (2, 2) on the curves $y^2 = 2x$ and $x^2 + y^2 = 4x$, and the line $x + y + 2 = 0$. If $r$ is the radius of its circumcircle, then $r^2$ is equal to _______.
Answer: 10
Solution
Given $S_1 : y^2 = 2x$ and $S_2 : x^2 + y^2 = 4x$. The point $P(2,2)$ is a common point on $S_1$ and $S_2$. $T_1$ is tangent to $S_1$ at $P$, therefore $T_1 : y \cdot 2 = x + 2$. This implies $T_1 : x - 2y + 2 = 0$. $T_2$ is tangent to $S_2$ at $P$, therefore $T_2 : x \cdot 2 + y \cdot 2 = 2(x+2)$. This implies $T_2 : y = 2$. And $L_3 : x + y + 2 = 0$ is the third line. For the triangle $\triangle PQR$, $$PQ = a = \sqrt{20}$$ $$QR = b = \sqrt{8}$$ $$RP = c = 6$$ The area of $\triangle PQR = \Delta = \frac{1}{2} \times 6 \times 2 = 6$. Therefore, $\frac{abc}{4\Delta} = \frac{\sqrt{160}}{4} = \sqrt{10} \implies r^2 = 10$.
Question 72
Maths · Conic Sections · Single correct
If the tangent at a point P on the parabola $y^2 = 3x$ is parallel to the line $x + 2y = 1$ and the tangents at the points Q and R on the ellipse $\frac{x^2}{4} + \frac{y^2}{1} = 1$ are perpendicular to the line $x - y = 2$, then the area of the triangle PQR is:
The statement $B \Rightarrow ((\sim A) \lor B)$ is equivalent to
$B \Rightarrow (A \Rightarrow B)$
$A \Rightarrow (A \Rightarrow B)$
$A \Rightarrow ((\sim A) \Rightarrow B)$
$B \Rightarrow ((\sim A) \Rightarrow B)$
Answer: (b)
Solution
\begin{tabular}{|l|l|l|l|} \hline p & q & (p $\rightarrow$ q) & (p $\lor$ q) & (p $\rightarrow$ q) $\land$ (p $\lor$ q) \\ \hline T & T & F & T & T \\ \hline T & F & F & F & T \\ \hline F & T & T & T & T \\ \hline F & F & T & T & T \\ \hline \end{tabular} \begin{tabular}{|l|l|l|l|} \hline A $\Rightarrow$ B & $\neg$ A $\Rightarrow$ B & B $\Rightarrow$ (A $\Rightarrow$ B) & A $\Rightarrow$ (($\neg$ A) $\Rightarrow$ B) & B $\Rightarrow$ (($\neg$ A) $\Rightarrow$ B) \\ \hline T & T & T & T & T \\ \hline F & T & T & T & T \\ \hline T & T & T & T & T \\ \hline T & F & T & T & T \\ \hline \end{tabular}
Question 74
Maths · Statistics · Numerical
Let X = {11, 12, 13, $\ldots$, 40, 41$\}$ and Y = {61, 62, 63, $\ldots$, 90, 91$\}$ be the two sets of observations. If $\bar{x}$ and $\bar{y}$ are their respective means and $\sigma^2$ is the variance of all the observations in X $\cup$ Y, then | $\bar{x}$ + $\bar{y}$ - $\sigma^2$| is equal to .
Let R be a relation defined on $\mathbb{N}$ as $a \, R \, b$ is $2a + 3b$ is a multiple of 5, $a, b \in \mathbb{N}$. Then R is
not reflexive
transitive but not symmetric
symmetric but not transitive
an equivalence relation
Answer: (d)
Solution
Given $a \, R \, a \Rightarrow 5a$ is multiple of $5$. So reflexive. $a \, R \, b \Rightarrow 2a + 3b = 5\alpha$. Now $b \, R \, a$. $$2b + 3a = 2b + \left(\frac{5\alpha - 3b}{2}\right) \cdot 3$$ $$= \frac{15}{2}\alpha - \frac{5}{2}b = \frac{5}{2}(3\alpha - b)$$ $$= \frac{5}{2}(2a + 2b - 2\alpha)$$ $$= 5(a + b - \alpha)$$ Hence symmetric. $a \, R \, b \Rightarrow 2a + 3b = 5\alpha$. $b \, R \, c \Rightarrow 2b + 3c = 5\beta$. Now $$2a + 5b + 3c = 5(\alpha + \beta)$$ $$\Rightarrow 2a + 5b + 3c = 5(\alpha + \beta)$$ $$\Rightarrow 2a + 3c = 5(\alpha + \beta - b)$$ $$\Rightarrow a \, R \, c$$ Hence relation is equivalence relation.
Question 76
Maths · Matrices · Single correct
The set of all values of $t \in \mathbb{R}$, for which the matrix $$\begin{bmatrix} e^t & e^{-t}(\sin t - 2 \cos t) & e^{-t}(-2 \sin t - \cos t) \\ e^t & e^{-t}(2 \sin t + \cos t) & e^{-t}(\sin t - 2 \cos t) \\ e^t & e^{-t} \cos t & e^{-t} \sin t \end{bmatrix}$$ is invertible, is
If it is invertible, then determinant value $\neq 0$. So, $$\begin{vmatrix} e^t & e^{-t}(\sin t - 2 \cos t) & e^{-t}(-2 \sin t - \cos t) \\ e^t & e^{-t}(2 \sin t + \cos t) & e^{-t}(\sin t - 2 \cos t) \\ e^t & e^{-t} \cos t & e^{-t} \sin t \end{vmatrix} \neq 0$$ $$\Rightarrow e^t \cdot e^{-t} \cdot e^{-t} \begin{vmatrix} 1 & \sin t - 2 \cos t & -2 \sin t - \cos t \\ 1 & 2 \sin t + \cos t & \sin t - 2 \cos t \\ 1 & \cos t & \sin t \end{vmatrix} \neq 0$$ Applying, $R_1 \rightarrow R_1 - R_2$ then $R_2 \rightarrow R_2 - R_3$, we get $$e^{-t} \begin{vmatrix} 0 & -\sin t - \cos t & -3 \sin t + \cos t \\ 0 & 2 \sin t & -2 \cos t \\ 1 & \cos t & \sin t \end{vmatrix} \neq 0$$ By expanding we have, $$e^{-t} \times 1 (2 \sin t \cos t + 6 \cos^2 t + 6 \sin^2 t - 2 \sin t \cos t) \neq 0$$ $$\Rightarrow e^{-t} \times 6 \neq 0$$ for $\forall \ t \in \mathbb{R}$
Question 77
Maths · Matrices · Numerical
Let A be a symmetric matrix such that $|A| = 2$ and $$\begin{bmatrix} 2 & 1 \\ 3 & \frac{3}{2} \end{bmatrix} A = \begin{bmatrix} 1 & 2 \\ \alpha & \beta \end{bmatrix}$$. If the sum of the diagonal elements of $A$ is $s$, then $\frac{\beta s}{\alpha^2}$ is equal to .
Answer: 5
Solution
Now $ac - b^2 = 2$ and $2a + b = 1$ and $2b + c = 2$. Solving all these above equations we get $$\frac{1-b}{2} \times \frac{(2-2b)}{1} - b^2 = 2$$ $$\Rightarrow (1-b)^2 - b^2 = 2$$ $$\Rightarrow 1 - 2b = 2$$ $$\Rightarrow b = -\frac{1}{2} and a = \frac{3}{4} and c = 3$$ Hence $\alpha = 3a + \frac{3b}{2} = \frac{9}{4} - \frac{3}{4} = \frac{3}{2}$ and $\beta = 3b + \frac{3c}{2} = -\frac{3}{2} + \frac{9}{2} = 3$. Also $s = a + c = \frac{15}{4}$. Therefore, $$\frac{\beta s}{\alpha^2} = \frac{3 \times 15}{4 \times \frac{9}{4}} = 5$$
Question 78
Maths · Relations and Functions · Single correct
Consider a function $f : \mathbb{N} \to \mathbb{R}$, satisfying $f(1) + 2f(2) + 3f(3) + \ldots + xf(x) = x(x+1) f(x); \ x \geq 2$ with $f(1)=1$. Then $\frac{1}{f(2022)} + \frac{1}{f(2028)}$ is equal to
Maths · Continuity and Differentiability · Single correct
Let f and g be twice differentiable functions on R such that $$f''(x) = g''(x) + 6x$$ $$f'(1) = 4g'(1) - 3 = 9$$ $$f(2) = 3g(2) = 12$$ Then which of the following is NOT true?
$g(-2) - f(-2) = 20$
If $-1 < x < 2$, then $|f(x) - g(x)| < 8$
$|f'(x) - g'(x)| < 6 \Rightarrow -1 < x < 1$
There exists $x_0 \in \left(1, \frac{3}{2}\right)$ such that $f(x_0) = g(x_0)$
Maths · Applications of Derivatives · Fill in the blank
If the equation of the normal to the curve $$y = \frac{x-a}{(x+b)(x-2)}$$ at the point (1, -3) is $x - 4y = 13$, then the value of $a + b$ is equal to _____.
Answer: 4
Solution
Given $\($ y = $\frac{x-a}{(x+b)(x-2)}$ $\)$. At point $\($(1, -3)$\)$, $\[$ -3 = $\frac{1-9}{(1+b)(1-2)}$ $\]$ $\($ $\Rightarrow$ 1-a = 3(1+b) $\)$ $\($ $\ldots$ $\)$ (1) Now, $\($ y = $\frac{x-a}{(x+b)(x-2)}$ $\)$ $\[$ $\Rightarrow$ $\frac{dy}{dx}$ = $\frac{(x+b)(x-2)(1)-(x-a)(2x+b-2)}{(x+b)^2(x-2)^2}$ $\]$ At $\($(1, -3)$\)$ slope of normal is $\($ $\frac{1}{4}$ $\)$ hence $\($ $\frac{dy}{dx}$ = -4 $\)$, So, $\[$ -4 = $\frac{(1+b)(-1)-(1-a)b}{(1+b)^2(-1)^2}$ $\]$ Using equation (1) $\[$ $\Rightarrow$ -4 = $\frac{(1+b)(-1)-3(b+1)b}{(1+b)^2}$ $\]$ $\[$ $\Rightarrow$ -4 = $\frac{(-1)-3b}{(1+b)}$ (b $\neq$ -1) $\]$ $\($ $\Rightarrow$ b = -3 $\)$ So, $\($ a = 7 $\)$ Hence, $\($ a+b = 7-3 = 4 $\)$
Question 81
Maths · Integrals · Single correct
The value of the integral $$\int_{1}^{2} \left( \frac{t^4 + 1}{t^6 + 1} \right) dt$$ is
Maths · Applications of Integrals · Single correct
The area of the region $$A = \left\{ (x, y) : |\cos x - \sin x| \leq y \leq \sin x, 0 \leq x \leq \frac{\pi}{2} \right\}$$
$1 - \frac{3}{\sqrt{2}} + \frac{4}{\sqrt{5}}$
$\sqrt{5} + 2\sqrt{2} - 4.5$
$\frac{3}{\sqrt{5}} - \frac{3}{\sqrt{2}} + 1$
$\sqrt{5} - 2\sqrt{2} + 1$
Answer: (d)
Solution
Given $|\cos x - \sin x| \leq y \leq \sin x$. Intersection point of $\cos x - \sin x = \sin x$ implies $\tan x = \frac{1}{2}$. Let $\psi = \tan^{-1} \frac{1}{2}$. So, $\tan \psi = \frac{1}{2}$, $\sin \psi = \frac{1}{\sqrt{5}}$, $\cos \psi = \frac{2}{\sqrt{5}}$. Area $= \int_{\psi}^{\pi/2} (\sin x - |\cos x - \sin x|) \, dx$ $= \int_{\psi}^{\pi/4} (\sin x - (\cos x - \sin x)) \, dx$ $+ \int_{\pi/4}^{\pi/2} (\sin x - (\sin x - \cos x)) \, dx$ $= \int_{\psi}^{\pi/4} (2 \sin x - \cos x) \, dx + \int_{\pi/4}^{\pi/2} \cos x \, dx$ $= [-2 \cos x - \sin x]_{\psi}^{\pi/4} + [\sin x]_{\pi/4}^{\pi/2}$ $= -\sqrt{2} - \frac{1}{\sqrt{2}} + 2 \cos \psi + \sin \psi + \left(1 - \frac{1}{\sqrt{2}}\right)$
Question 84
Maths · Differential Equations · Single correct
Let $y = y(x)$ be the solution of the differential equation $x \log_e x \frac{dy}{dx} + y = x^2 \log_e x$, $(x > 1)$. If $y(2) = 2$, then $y(e)$ is equal to
If $\vec{a} = \hat{i} + 2\hat{k}$, $\vec{b} = \hat{i} + \hat{j} + \hat{k}$, $\vec{c} = 7\hat{i} - 3\hat{k} + 4\hat{k}$, $\vec{r} \times \vec{b} + \vec{b} \times \vec{c} = \vec{0}$ and $\vec{r} \cdot \vec{a} = 0$ then $\vec{r} \cdot \vec{c}$ is equal to
34
12
36
30
Answer: (a)
Solution
$$\vec{r}\times\vec{b}-\vec{c}\times\vec{b}=0$$ $$\Rightarrow (\vec{r}-\vec{c})\times\vec{b}=0$$ $$\Rightarrow \vec{r}-\vec{c}=\lambda\vec{b}$$ $$\Rightarrow \vec{r}=\vec{c}+\lambda\vec{b}$$ And given that $$\vec{r}\cdot\vec{a}=0$$ $$\Rightarrow (\vec{c}+\lambda\vec{b})\cdot\vec{a}=0$$ $$\Rightarrow \vec{c}\cdot\vec{a}+\lambda\,\vec{b}\cdot\vec{a}=0$$ $$\Rightarrow \lambda=\frac{-\,\vec{c}\cdot\vec{a}}{\vec{b}\cdot\vec{a}}$$ Now $$\vec{r}\cdot\vec{c}=(\vec{c}+\lambda\vec{b})\cdot\vec{c}$$ $$=\left(\vec{c}-\frac{\vec{c}\cdot\vec{a}}{\vec{b}\cdot\vec{a}}\vec{b}\right)\cdot\vec{c}$$ $$=|\vec{c}|^{2}-\left(\frac{\vec{c}\cdot\vec{a}}{\vec{b}\cdot\vec{a}}\right)(\vec{b}\cdot\vec{c})$$ $$=74-\left(\frac{15}{3}\right)8$$ $$=74-40=34$$
Question 86
Maths · Vector Algebra · Single correct
Let $\vec{a}=4\hat{i}+3\hat{j}$ and $\vec{b}=3\hat{i}-4\hat{j}+5\hat{k}$ and $\vec{c}$ is a vector such that \[ \vec{c}\cdot(\vec{a}\times\vec{b})+25=0, \qquad \vec{c}\cdot(\hat{i}+\hat{j}+\hat{k})=4 \] and projection of $\vec{c}$ on $\vec{a}$ is $1$, then the projection of $\vec{c}$ on $\vec{b}$ equals:
$\frac{5}{\sqrt{2}}$
$\frac{1}{5}$
$\frac{1}{\sqrt{2}}$
$\frac{3}{\sqrt{2}}$
Answer: (a)
Solution
Given $\vec{a} \times \vec{b} = 15\hat{i} - 20\hat{j} - 25\hat{k}$. Let $\vec{c} = x\hat{i} + y\hat{j} + z\hat{k}$. Therefore, $15x - 20y - 25z + 25 = 0$. This simplifies to $3x - 4y - 5z = -5$. Also, $x + y + z = 4$. And $\frac{\vec{c} \cdot \vec{a}}{|\vec{a}|} = 1$ implies $4x + 3y = 5$. Therefore, $\vec{c} = 2\hat{i} - \hat{j} + 3\hat{k}$. The projection of $\vec{c}$ or $\vec{b}$ is $\frac{25}{5\sqrt{2}} = \frac{5}{\sqrt{2}}$.
Question 87
Maths · Three Dimensional Geometry · Single correct
Shortest distance between the lines $\($ $\frac{x-1}{2}$ = $\frac{y+8}{-7}$ = $\frac{z-4}{5}$ $\)$ and $\($ $\frac{x-1}{2}$ = $\frac{y-2}{1}$ = $\frac{z-6}{-3}$ $\)$ is
Maths · Three Dimensional Geometry · Single correct
The plane $2x - y + z = 4$ intersects the line segment joining the points $A(a, -2, 4)$ and $B(2, b, -3)$ at the point $C$ in the ratio $2 : 1$ and the distance of the point $C$ from the origin is $\sqrt{5}$. If $ab < 0$ and $P$ is the point $(a - b, b, 2b - a)$ then $CP^2$ is equal to:
$\($ $\frac{17}{3}$ $\)$
$\($ $\frac{16}{3}$ $\)$
$\($ $\frac{73}{3}$ $\)$
$\($ $\frac{97}{3}$ $\)$
Answer: (a)
Solution
Given points A(a, -2, 4), B(2, b, -3). The ratio AC : CB = 2 : 1. Therefore, $$C \equiv \left( \frac{a+4}{3}, \frac{2b-2}{3}, \frac{-2}{3} \right)$$ C lies on the line $2x - y + 2 = 4$. Thus, $$\frac{2a+8}{3} - \frac{2b-2}{3} - \frac{2}{3} = 4$$ This implies $a - b = 2 \ldots (1)$ Also, $OC = \sqrt{5}$ Therefore, $$\left( \frac{a+4}{3} \right)^2 + \left( \frac{2b-2}{3} \right)^2 + \frac{4}{9} = 5 \ldots (2)$$ Solving equations (1) and (2), $$(b+6)^2 + (2b-2)^2 = 41$$ This implies $$5b^2 + 4b - 1 = 0$$ Thus, $b = -1$ or $\frac{1}{5}$ Therefore, $a = 1$ or $\frac{11}{5}$ But $ab < 0$ implies $(a, b) = (1, -1)$ Thus, $$C \equiv \left( \frac{5}{3}, -\frac{4}{3}, -\frac{2}{3} \right), \ P \equiv (2, -1, -3)$$ Finally, $$CP^2 = \frac{1}{9} + \frac{1}{9} + \frac{49}{9} = \frac{51}{9} = \frac{17}{3}$$
Question 89
Maths · Three Dimensional Geometry · Single correct
If the lines $\frac{x-1}{1} = \frac{y-2}{2} = \frac{z+3}{1}$ and $\frac{x-a}{2} = \frac{y+2}{3} = \frac{z-3}{1}$ intersects at the point P, then the distance of the point P from the plane $z = a$ is:
16
28
10
22
Answer: (b)
Solution
Point on $L_1 \equiv (\lambda + 1, 2\lambda + 2, \lambda - 3)$ Point on $L_2 \equiv (2\mu + a, 3\mu - 2, \mu + 3)$ $\lambda - 3 = \mu + 3 \Rightarrow \lambda = \mu + 6 \ldots (1)$ $2\lambda + 2 = 3\mu - 2 \Rightarrow 2\lambda = 3\mu - 4 \ldots (2)$ Solving, (1) and (2) $\Rightarrow \lambda = 22 and \mu = 16$ $\Rightarrow P \equiv (23, 46, 19)$ $\Rightarrow a = -9$
Question 90
Maths · Probability · Single correct
Let \(S=\{w_1,w_2,\ldots\}\) be the sample space associated with a random experiment. Let \[ P(w_n)=\frac{P(w_{n-1})}{2}, \qquad n\ge 2. \] Let \[ A=\{2k+3\ell \,;\, k,\ell\in\mathbb{N}\} \] and \[ B=\{w_n \,;\, n\in A\}. \] Then \(P(B)\) is equal to