AIEEE 2012 — 29 Apr Offline Set C (Previous Year Paper)

JEE Main · 2012 · with answers and explanations

questions
87
Total marks
348
Duration
180 minutes
Negative marking
−1

Subjects: Mathematics · Physics · Chemistry

Question 1

Mathematics · 4 marks · −1

The equation esin⁡x−e−sin⁡x−4=0e^{\sin x} - e^{-\sin x} - 4 = 0 has

  1. A.infinite number of real roots
  2. B.no real roots
  3. C.exactly one real root
  4. D.exactly four real roots

Correct answer: B

Explanation: With t=esin⁡xt=e^{\sin x}: t2−4t−1=0t^2-4t-1=0, t=2±5t=2\pm\sqrt5; but t∈[e−1,e]t\in[e^{-1},e], so no solution.

Question 2

Mathematics · 4 marks · −1

Let a^\hat{a} and b^\hat{b} be two unit vectors. If the vectors c⃗=a^+2b^\vec{c} = \hat{a} + 2\hat{b} and d⃗=5a^−4b^\vec{d} = 5\hat{a} - 4\hat{b} are perpendicular to each other, then the angle between a^\hat{a} and b^\hat{b} is

  1. A.π6\frac{\pi}{6}
  2. B.π2\frac{\pi}{2}
  3. C.π3\frac{\pi}{3}
  4. D.π4\frac{\pi}{4}

Correct answer: C

Explanation: 5+6a^⋅b^−8=0⇒a^⋅b^=125+6\hat a\cdot\hat b-8=0\Rightarrow\hat a\cdot\hat b=\frac12.

Question 3

Mathematics · 4 marks · −1

A spherical balloon is filled with 4500π4500\pi cubic meters of helium gas. If a leak in the balloon causes the gas to escape at the rate of 72π72\pi cubic meters per minute, then the rate (in meters per minute) at which the radius of the balloon decreases 49 minutes after the leakage began is

  1. A.97\frac{9}{7}
  2. B.79\frac{7}{9}
  3. C.29\frac{2}{9}
  4. D.92\frac{9}{2}

Correct answer: C

Explanation: After 49 min V=972π⇒r=9V=972\pi\Rightarrow r=9; 72π=4πr2drdt⇒drdt=2972\pi=4\pi r^2\frac{dr}{dt}\Rightarrow\frac{dr}{dt}=\frac29.

Question 4

Mathematics · 4 marks · −1

Statement 1: The sum of the series 1+(1+2+4)+(4+6+9)+(9+12+16)+⋯+(361+380+400)1 + (1 + 2 + 4) + (4 + 6 + 9) + (9 + 12 + 16) + \dots + (361 + 380 + 400) is 8000. Statement 2: ∑k=1n(k3−(k−1)3)=n3\sum_{k=1}^{n}\left(k^3 - (k-1)^3\right) = n^3 for any natural number n.

  1. A.Statement 1 is false, statement 2 is true
  2. B.Statement 1 is true, statement 2 is true; statement 2 is a correct explanation for statement 1
  3. C.Statement 1 is true, statement 2 is true; statement 2 is not a correct explanation for statement 1
  4. D.Statement 1 is true, statement 2 is false

Correct answer: B

Explanation: The k-th bracket is (k−1)2+k(k−1)+k2=k3−(k−1)3(k-1)^2+k(k-1)+k^2=k^3-(k-1)^3; 20 brackets telescope to 203=800020^3=8000, so Statement 2 explains Statement 1.

Question 5

Mathematics · 4 marks · −1

The negation of the statement 'If I become a teacher, then I will open a school' is

  1. A.I will become a teacher and I will not open a school
  2. B.Either I will not become a teacher or I will not open a school
  3. C.Neither I will become a teacher nor I will open a school
  4. D.I will not become a teacher or I will open a school

Correct answer: A

Explanation: ∼(p→q)≡p∧∼q\sim(p\to q)\equiv p\wedge\sim q.

Question 6

Mathematics · 4 marks · −1

If the integral ∫5tan⁡xtan⁡x−2 dx=x+aln⁡∣sin⁡x−2cos⁡x∣+k\int\frac{5\tan x}{\tan x - 2}\,dx = x + a\ln|\sin x - 2\cos x| + k, then a is equal to

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

Correct answer: D

Explanation: 5sin⁡x=2(cos⁡x+2sin⁡x)+(sin⁡x−2cos⁡x)5\sin x=2(\cos x+2\sin x)+(\sin x-2\cos x), so the integral is 2ln⁡∣sin⁡x−2cos⁡x∣+x2\ln|\sin x-2\cos x|+x.

Question 7

Mathematics · 4 marks · −1

Statement 1: An equation of a common tangent to the parabola y2=163xy^2 = 16\sqrt{3}x and the ellipse 2x2+y2=42x^2 + y^2 = 4 is y=2x+23y = 2x + 2\sqrt{3}. Statement 2: If the line y=mx+43my = mx + \frac{4\sqrt{3}}{m}, (m≠0)(m \ne 0) is a common tangent to the parabola y2=163xy^2 = 16\sqrt{3}x and the ellipse 2x2+y2=42x^2 + y^2 = 4, then m satisfies m4+2m2=24m^4 + 2m^2 = 24.

  1. A.Statement 1 is false, statement 2 is true
  2. B.Statement 1 is true, statement 2 is true; statement 2 is a correct explanation for statement 1
  3. C.Statement 1 is true, statement 2 is true; statement 2 is not a correct explanation for statement 1
  4. D.Statement 1 is true, statement 2 is false

Correct answer: B

Explanation: Tangency to x22+y24=1\frac{x^2}{2}+\frac{y^2}{4}=1: 48m2=2m2+4⇒m4+2m2=24\frac{48}{m^2}=2m^2+4\Rightarrow m^4+2m^2=24, m2=4m^2=4; m=2m=2 gives y=2x+23y=2x+2\sqrt3.

Question 8

Mathematics · 4 marks · −1

Let A=(100210321)A = \begin{pmatrix} 1 & 0 & 0 \\ 2 & 1 & 0 \\ 3 & 2 & 1 \end{pmatrix}. If u1u_1 and u2u_2 are column matrices such that Au1=(100)Au_1 = \begin{pmatrix} 1 \\ 0 \\ 0 \end{pmatrix} and Au2=(010)Au_2 = \begin{pmatrix} 0 \\ 1 \\ 0 \end{pmatrix}, then u1+u2u_1 + u_2 is equal to

  1. A.(−110)\begin{pmatrix} -1 \\ 1 \\ 0 \end{pmatrix}
  2. B.(−11−1)\begin{pmatrix} -1 \\ 1 \\ -1 \end{pmatrix}
  3. C.(−1−10)\begin{pmatrix} -1 \\ -1 \\ 0 \end{pmatrix}
  4. D.(1−1−1)\begin{pmatrix} 1 \\ -1 \\ -1 \end{pmatrix}

Correct answer: D

Explanation: Forward substitution: u1=(1,−2,1)Tu_1=(1,-2,1)^T, u2=(0,1,−2)Tu_2=(0,1,-2)^T; sum (1,−1,−1)T(1,-1,-1)^T.

Question 9

Mathematics · 4 marks · −1

If n is a positive integer, then (3+1)2n−(3−1)2n\left(\sqrt{3}+1\right)^{2n} - \left(\sqrt{3}-1\right)^{2n} is

  1. A.an irrational number
  2. B.an odd positive integer
  3. C.an even positive integer
  4. D.a rational number other than positive integers

Correct answer: A

Explanation: =(4+23)n−(4−23)n=(4+2\sqrt3)^n-(4-2\sqrt3)^n; only odd powers of 3\sqrt3 survive, giving an integer multiple of 3\sqrt3.

Question 10

Mathematics · 4 marks · −1

If 100 times the 100th100^{th} term of an AP with non zero common difference equals the 50 times its 50th50^{th} term, then the 150th150^{th} term of this AP is

  1. A.−150-150
  2. B.150 times its 50th50^{th} term
  3. C.150
  4. D.zero

Correct answer: D

Explanation: 100(a+99d)=50(a+49d)⇒a+149d=0=T150100(a+99d)=50(a+49d)\Rightarrow a+149d=0=T_{150}.

Question 11

Mathematics · 4 marks · −1

In a △PQR\triangle PQR, if 3sin⁡P+4cos⁡Q=63\sin P + 4\cos Q = 6 and 4sin⁡Q+3cos⁡P=14\sin Q + 3\cos P = 1, then the angle R is equal to

  1. A.5π6\frac{5\pi}{6}
  2. B.π6\frac{\pi}{6}
  3. C.π4\frac{\pi}{4}
  4. D.3π4\frac{3\pi}{4}

Correct answer: B

Explanation: Squaring and adding: 25+24sin⁡(P+Q)=37⇒sin⁡(P+Q)=1225+24\sin(P+Q)=37\Rightarrow\sin(P+Q)=\frac12. If P+Q=π6P+Q=\frac\pi6 then P<π6P<\frac\pi6 and 3sin⁡P+4cos⁡Q<32+4<63\sin P+4\cos Q<\frac32+4<6, impossible; so P+Q=5π6P+Q=\frac{5\pi}6 and R=π6R=\frac\pi6.

Question 12

Mathematics · 4 marks · −1

An equation of a plane parallel to the plane x−2y+2z−5=0x - 2y + 2z - 5 = 0 and at a unit distance from the origin is

  1. A.x−2y+2z−3=0x - 2y + 2z - 3 = 0
  2. B.x−2y+2z+1=0x - 2y + 2z + 1 = 0
  3. C.x−2y+2z−1=0x - 2y + 2z - 1 = 0
  4. D.x−2y+2z+5=0x - 2y + 2z + 5 = 0

Correct answer: A

Explanation: ∣k∣3=1⇒k=±3\frac{|k|}{3}=1\Rightarrow k=\pm3.

Question 13

Mathematics · 4 marks · −1

If the line 2x+y=k2x + y = k passes through the point which divides the line segment joining the points (1, 1) and (2, 4) in the ratio 3 : 2, then k equals

  1. A.295\frac{29}{5}
  2. B.5
  3. C.6
  4. D.115\frac{11}{5}

Correct answer: C

Explanation: Point (85,145)\left(\frac85,\frac{14}5\right); k=16+145=6k=\frac{16+14}{5}=6.

Question 14

Mathematics · 4 marks · −1

Let x1,x2,…,xnx_1, x_2, \dots, x_n be n observations, and let xˉ\bar{x} be their arithmetic mean and σ2\sigma^2 be their variance. Statement 1: Variance of 2x1,2x2,…,2xn2x_1, 2x_2, \dots, 2x_n is 4σ24\sigma^2. Statement 2: Arithmetic mean of 2x1,2x2,…,2xn2x_1, 2x_2, \dots, 2x_n is 4xˉ4\bar{x}.

  1. A.Statement 1 is false, statement 2 is true
  2. B.Statement 1 is true, statement 2 is true; statement 2 is a correct explanation for statement 1
  3. C.Statement 1 is true, statement 2 is true; statement 2 is not a correct explanation for statement 1
  4. D.Statement 1 is true, statement 2 is false

Correct answer: D

Explanation: Scaling by 2 multiplies variance by 4 but the mean only by 2.

Question 15

Mathematics · 4 marks · −1

The population p(t) at time t of a certain mouse species satisfies the differential equation dp(t)dt=0.5 p(t)−450\frac{dp(t)}{dt} = 0.5\,p(t) - 450. If p(0)=850p(0) = 850, then the time at which the population becomes zero is

  1. A.2ln⁡182\ln18
  2. B.ln⁡9\ln9
  3. C.12ln⁡18\frac{1}{2}\ln18
  4. D.ln⁡18\ln18

Correct answer: A

Explanation: p−900=−50et/2p-900=-50e^{t/2}; p=0⇒et/2=18p=0\Rightarrow e^{t/2}=18, t=2ln⁡18t=2\ln18.

Question 16

Mathematics · 4 marks · −1

Let a,b∈Ra, b \in \mathbb{R} be such that the function f given by f(x)=ln⁡∣x∣+bx2+axf(x) = \ln|x| + bx^2 + ax, x≠0x \ne 0 has extreme values at x=−1x = -1 and x=2x = 2. Statement 1: f has local maximum at x=−1x = -1 and at x=2x = 2. Statement 2: a=12a = \frac{1}{2} and b=−14b = \frac{-1}{4}.

  1. A.Statement 1 is false, statement 2 is true
  2. B.Statement 1 is true, statement 2 is true; statement 2 is a correct explanation for statement 1
  3. C.Statement 1 is true, statement 2 is true; statement 2 is not a correct explanation for statement 1
  4. D.Statement 1 is true, statement 2 is false

Correct answer: B

Explanation: f′(−1)=f′(2)=0f'(-1)=f'(2)=0 give a=12a=\frac12, b=−14b=-\frac14; then f′′(x)=−1x2−12<0f''(x)=-\frac1{x^2}-\frac12<0 at both points, so both are maxima.

Question 17

Mathematics · 4 marks · −1

The area bounded between the parabolas x2=y4x^2 = \frac{y}{4} and x2=9yx^2 = 9y, and the straight line y=2y = 2 is

  1. A.20220\sqrt{2}
  2. B.1023\frac{10\sqrt{2}}{3}
  3. C.2023\frac{20\sqrt{2}}{3}
  4. D.10210\sqrt{2}

Correct answer: C

Explanation: A=2∫02(3y−y2)dy=5⋅23⋅23/2=2023A=2\int_0^2\left(3\sqrt y-\frac{\sqrt y}{2}\right)dy=5\cdot\frac23\cdot2^{3/2}=\frac{20\sqrt2}{3}.

Question 18

Mathematics · 4 marks · −1

Assuming the balls to be identical except for difference in colours, the number of ways in which one or more balls can be selected from 10 white, 9 green and 7 black balls is

  1. A.880
  2. B.629
  3. C.630
  4. D.879

Correct answer: D

Explanation: 11⋅10⋅8−1=87911\cdot10\cdot8-1=879.

Question 19

Mathematics · 4 marks · −1

If f:R→Rf : \mathbb{R} \to \mathbb{R} is a function defined by f(x)=[x]cos⁡(2x−12)πf(x) = [x]\cos\left(\frac{2x-1}{2}\right)\pi, where [x] denotes the greatest integer function, then f is

  1. A.continuous for every real x
  2. B.discontinuous only at x=0x = 0
  3. C.discontinuous only at non-zero integral values of x
  4. D.continuous only at x=0x = 0

Correct answer: A

Explanation: f(x)=[x]sin⁡πxf(x)=[x]\sin\pi x; at integers sin⁡πx=0\sin\pi x=0 kills the jump of [x][x].

Question 20

Mathematics · 4 marks · −1

If the lines x−12=y+13=z−14\frac{x-1}{2} = \frac{y+1}{3} = \frac{z-1}{4} and x−31=y−k2=z1\frac{x-3}{1} = \frac{y-k}{2} = \frac{z}{1} intersect, then k is equal to

  1. A.−1-1
  2. B.29\frac{2}{9}
  3. C.92\frac{9}{2}
  4. D.0

Correct answer: C

Explanation: (2t+1,3t−1,4t+1)=(s+3,2s+k,s)(2t+1,3t-1,4t+1)=(s+3,2s+k,s): t=−32t=-\frac32, s=−5s=-5, k=92k=\frac92.

Question 21

Mathematics · 4 marks · −1

Three numbers are chosen at random without replacement from {1, 2, 3, ......, 8}. The probability that their minimum is 3, given that their maximum is 6, is

  1. A.38\frac{3}{8}
  2. B.15\frac{1}{5}
  3. C.14\frac{1}{4}
  4. D.25\frac{2}{5}

Correct answer: B

Explanation: Given max 6: (52)=10\binom52=10 choices for the other two; min 3 needs 3 and one of {4,5}: 2. Probability 15\frac15.

Question 22

Mathematics · 4 marks · −1

If z≠1z \ne 1 and z2z−1\frac{z^2}{z-1} is real, then the point represented by the complex number z lies

  1. A.either on the real axis or on a circle passing through the origin
  2. B.on a circle with centre at the origin
  3. C.either on the real axis or on a circle not passing through the origin
  4. D.on the imaginary axis

Correct answer: A

Explanation: Imaginary part zero gives y(x2+y2−2x)=0y(x^2+y^2-2x)=0.

Question 23

Mathematics · 4 marks · −1

Let P and Q be 3×33\times3 matrices with P≠QP \ne Q. If P3=Q3P^3 = Q^3 and P2Q=Q2PP^2Q = Q^2P, then determinant of (P2+Q2)(P^2 + Q^2) is equal to

  1. A.−2-2
  2. B.1
  3. C.0
  4. D.−1-1

Correct answer: C

Explanation: (P2+Q2)(P−Q)=P3−P2Q+Q2P−Q3=0(P^2+Q^2)(P-Q)=P^3-P^2Q+Q^2P-Q^3=0 with P−Q≠0P-Q\ne0, so P2+Q2P^2+Q^2 is singular.

Question 24

Mathematics · 4 marks · −1

The length of the diameter of the circle which touches the x-axis at the point (1, 0) and passes through the point (2, 3) is

  1. A.103\frac{10}{3}
  2. B.35\frac{3}{5}
  3. C.65\frac{6}{5}
  4. D.53\frac{5}{3}

Correct answer: A

Explanation: Centre (1,k)(1,k): 1+(k−3)2=k2⇒k=531+(k-3)^2=k^2\Rightarrow k=\frac53; diameter 103\frac{10}3.

Question 25

Mathematics · 4 marks · −1

Let X = {1, 2, 3, 4, 5}. The number of different ordered pairs (Y, Z) that can be formed such that Y⊆XY \subseteq X, Z⊆XZ \subseteq X and Y∩ZY \cap Z is empty, is

  1. A.525^2
  2. B.353^5
  3. C.252^5
  4. D.535^3

Correct answer: B

Explanation: Each element is in Y only, Z only, or neither: 353^5.

Question 26

Mathematics · 4 marks · −1

An ellipse is drawn by taking a diameter of the circle (x−1)2+y2=1(x - 1)^2 + y^2 = 1 as its semiminor axis and a diameter of the circle x2+(y−2)2=4x^2 + (y - 2)^2 = 4 as its semi-major axis. If the centre of the ellipse is the origin and its axes are the coordinate axes, then the equation of the ellipse is

  1. A.4x2+y2=44x^2 + y^2 = 4
  2. B.x2+4y2=8x^2 + 4y^2 = 8
  3. C.4x2+y2=84x^2 + y^2 = 8
  4. D.x2+4y2=16x^2 + 4y^2 = 16

Correct answer: D

Explanation: b=2b=2, a=4a=4: x216+y24=1\frac{x^2}{16}+\frac{y^2}{4}=1.

Question 27

Mathematics · 4 marks · −1

Consider the function f(x)=∣x−2∣+∣x−5∣f(x) = |x - 2| + |x - 5|, x∈Rx \in \mathbb{R}. Statement 1: f′(4)=0f'(4) = 0. Statement 2: f is continuous in [2, 5], differentiable in (2, 5) and f(2)=f(5)f(2) = f(5).

  1. A.Statement 1 is false, statement 2 is true
  2. B.Statement 1 is true, statement 2 is true; statement 2 is a correct explanation for statement 1
  3. C.Statement 1 is true, statement 2 is true; statement 2 is not a correct explanation for statement 1
  4. D.Statement 1 is true, statement 2 is false

Correct answer: B

Explanation: f is constant (=3) on [2,5], so f′(4)=0f'(4)=0; Rolle's conditions in Statement 2 hold and explain it.

Question 28

Mathematics · 4 marks · −1

A line is drawn through the point (1, 2) to meet the coordinate axes at P and Q such that it forms a triangle OPQ, where O is the origin. If the area of the triangle OPQ is least, then the slope of the line PQ is

  1. A.−14-\frac{1}{4}
  2. B.−4-4
  3. C.−2-2
  4. D.−12-\frac{1}{2}

Correct answer: C

Explanation: Area =(2−m)22∣m∣=\frac{(2-m)^2}{2|m|} with m<0m<0 is least at m=−2m=-2 (area 4).

Question 29

Mathematics · 4 marks · −1

Let ABCD be a parallelogram such that AB⃗=q⃗\vec{AB} = \vec{q}, AD⃗=p⃗\vec{AD} = \vec{p} and ∠BAD\angle BAD be an acute angle. If r⃗\vec{r} is the vector that coincides with the altitude directed from the vertex B to the side AD, then r⃗\vec{r} is given by

Figure for question 29
  1. A.r⃗=3q⃗−3(p⃗⋅q⃗)(p⃗⋅p⃗)p⃗\vec{r} = 3\vec{q} - \frac{3(\vec{p}\cdot\vec{q})}{(\vec{p}\cdot\vec{p})}\vec{p}
  2. B.r⃗=−q⃗+(p⃗⋅q⃗p⃗⋅p⃗)p⃗\vec{r} = -\vec{q} + \left(\frac{\vec{p}\cdot\vec{q}}{\vec{p}\cdot\vec{p}}\right)\vec{p}
  3. C.r⃗=q⃗−(p⃗⋅q⃗p⃗⋅p⃗)p⃗\vec{r} = \vec{q} - \left(\frac{\vec{p}\cdot\vec{q}}{\vec{p}\cdot\vec{p}}\right)\vec{p}
  4. D.r⃗=−3q⃗+3(p⃗⋅q⃗)(p⃗⋅p⃗)p⃗\vec{r} = -3\vec{q} + \frac{3(\vec{p}\cdot\vec{q})}{(\vec{p}\cdot\vec{p})}\vec{p}

Correct answer: B

Explanation: Foot E on AD: AE⃗=p⃗⋅q⃗p⃗⋅p⃗p⃗\vec{AE}=\frac{\vec p\cdot\vec q}{\vec p\cdot\vec p}\vec p; r⃗=BE⃗=AE⃗−q⃗\vec r=\vec{BE}=\vec{AE}-\vec q.

Question 30

Physics · 4 marks · −1

A wooden wheel of radius R is made of two semicircular parts (see figure). The two parts are held together by a ring made of a metal strip of cross sectional area S and length L. L is slightly less than 2πR2\pi R. To fit the ring on the wheel, it is heated so that its temperature rises by ΔT\Delta T and it just steps over the wheel. As it cools down to surrounding temperature, it presses the semicircular parts together. If the coefficient of linear expansion of the metal is α\alpha, and its Youngs' modulus is Y, the force that one part of the wheel applies on the other part is :

Figure for question 30
  1. A.2πSYαΔT2\pi SY\alpha\Delta T
  2. B.SYαΔTSY\alpha\Delta T
  3. C.πSYαΔT\pi SY\alpha\Delta T
  4. D.2SYαΔT2SY\alpha\Delta T

Correct answer: D

Explanation: Ring tension T=SYαΔTT=SY\alpha\Delta T; each semicircle is pulled by 2T2T.

Question 31

Physics · 4 marks · −1

The figure shows an experimental plot for discharging of a capacitor in an R-C circuit. The time constant τ\tau of this circuit lies between:

Figure for question 31
  1. A.150 sec and 200 sec
  2. B.0 and 50 sec
  3. C.50 sec and 100 sec
  4. D.100 sec and 150 sec

Correct answer: D

Explanation: V falls from 25 V to 12.5 V in about 100 s: τ=100ln⁡2≈144\tau=\frac{100}{\ln2}\approx144 s.

Question 32

Physics · 4 marks · −1

In a uniformly charged sphere of total charge Q and radius R, the electric field E is plotted as a function of distance from the centre. The graph which would correspond to the above will be

Figure for question 32
  1. A.Graph (1)
  2. B.Graph (2)
  3. C.Graph (3)
  4. D.Graph (4)

Correct answer: C

Explanation: E rises linearly inside (∝r\propto r), peaks at R, then falls as 1r2\frac1{r^2}.

Question 33

Physics · 4 marks · −1

If a simple pendulum has significant amplitude (up to a factor of 1/e of original) only in the period between t=0t = 0 s to t=τt = \tau s, then τ\tau may be called the average life of the pendulum. When the spherical bob of the pendulum suffers a retardation (due to viscous drag) proportional to its velocity, with 'b' as the constant of proportionality, the average life time of the pendulum is (assuming damping is small) in seconds:

  1. A.0.693b\frac{0.693}{b}
  2. B.b
  3. C.1b\frac{1}{b}
  4. D.2b\frac{2}{b}

Correct answer: D

Explanation: Amplitude decays as e−bt/2e^{-bt/2}; it reaches 1/e1/e at τ=2b\tau=\frac2b.

Question 34

Physics · 4 marks · −1

Hydrogen atom is excited from ground state to another state with principal quantum number equal to 4. Then the number of spectral lines in the emission spectra will be

  1. A.2
  2. B.3
  3. C.5
  4. D.6

Correct answer: D

Explanation: n(n−1)2=6\frac{n(n-1)}{2}=6.

Question 35

Physics · 4 marks · −1

A coil is suspended in a uniform magnetic field, with the plane of the coil parallel to the magnetic lines of force. When a current is passed through the coil it starts oscillating; it is very difficult to stop. But if an aluminium plate is placed near to the coil, it stops. This is due to :

  1. A.development of air current when the plate is placed.
  2. B.induction of electrical charge on the plate
  3. C.shielding of magnetic lines of force as aluminium is a paramagnetic material.
  4. D.electromagnetic induction in the aluminium plate giving rise to electromagnetic damping.

Correct answer: D

Explanation: Eddy currents induced in the plate oppose the motion (electromagnetic damping).

Question 36

Physics · 4 marks · −1

The mass of a spaceship is 1000 kg. It is to be launched from the earth's surface out into free space. The value of 'g' and 'R' (radius of earth) are 10 m/s2^2 and 6400 km respectively. The required energy for this work will be ;

  1. A.6.4×10116.4\times10^{11} Joules
  2. B.6.4×1086.4\times10^8 Joules
  3. C.6.4×1096.4\times10^9 Joules
  4. D.6.4×10106.4\times10^{10} Joules

Correct answer: D

Explanation: E=GMmR=mgR=103⋅10⋅6.4×106=6.4×1010E=\frac{GMm}{R}=mgR=10^3\cdot10\cdot6.4\times10^6=6.4\times10^{10} J.

Question 37

Physics · 4 marks · −1

Helium gas goes through a cycle ABCDA (consisting of two isochoric and two isobaric lines) as shown in figure. Efficiency of this cycle is nearly: (Assume the gas to be close to ideal gas)

Figure for question 37
  1. A.15.4%
  2. B.9.1%
  3. C.10.5%
  4. D.12.5%

Correct answer: A

Explanation: Work =P0V0=P_0V_0; heat in: A to B 32P0V0\frac32P_0V_0, B to C 5P0V05P_0V_0. η=16.5≈15.4%\eta=\frac{1}{6.5}\approx15.4\%.

Question 38

Physics · 4 marks · −1

In Young's double slit experiment, one of the slit is wider than other, so that the amplitude of the light from one slit is double of that from other slit. If ImI_m be the maximum intensity, the resultant intensity I when they interfere at phase difference ϕ\phi is given by

  1. A.Im9(4+5cos⁡ϕ)\frac{I_m}{9}(4 + 5\cos\phi)
  2. B.Im3(1+2cos⁡2ϕ2)\frac{I_m}{3}\left(1 + 2\cos^2\frac{\phi}{2}\right)
  3. C.Im5(1+4cos⁡2ϕ2)\frac{I_m}{5}\left(1 + 4\cos^2\frac{\phi}{2}\right)
  4. D.Im9(1+8cos⁡2ϕ2)\frac{I_m}{9}\left(1 + 8\cos^2\frac{\phi}{2}\right)

Correct answer: D

Explanation: I∝1+4+4cos⁡ϕI\propto1+4+4\cos\phi, Im∝9I_m\propto9: I=Im9(5+4cos⁡ϕ)=Im9(1+8cos⁡2ϕ2)I=\frac{I_m}{9}(5+4\cos\phi)=\frac{I_m}{9}(1+8\cos^2\frac\phi2).

Question 39

Physics · 4 marks · −1

A liquid in a beaker has temperature θ(t)\theta(t) at time t and θ0\theta_0 is temperature of surroundings, then according to Newton's law of cooling the correct graph between log⁡e(θ−θ0)\log_e(\theta - \theta_0) and t is

Figure for question 39
  1. A.Graph (1)
  2. B.Graph (2)
  3. C.Graph (3)
  4. D.Graph (4)

Correct answer: A

Explanation: ln⁡(θ−θ0)=−kt+c\ln(\theta-\theta_0)=-kt+c: a straight line with negative slope.

Question 40

Physics · 4 marks · −1

A particle of mass m is at rest at the origin at time t=0t = 0. It is subjected to a force F(t)=F0e−btF(t) = F_0e^{-bt} in the x direction. Its speed v(t) is depicted by which of the following curves?

Figure for question 40
  1. A.Graph (1)
  2. B.Graph (2)
  3. C.Graph (3)
  4. D.Graph (4)

Correct answer: C

Explanation: v=F0mb(1−e−bt)v=\frac{F_0}{mb}(1-e^{-bt}), rising from 0 to the asymptote F0mb\frac{F_0}{mb}.

Question 41

Physics · 4 marks · −1

Two electric bulbs marked 25W - 220V and 100W - 220V are connected in series to a 440V supply. Which of the bulbs will fuse?

  1. A.both
  2. B.100 W
  3. C.25 W
  4. D.neither

Correct answer: C

Explanation: R25=4R100R_{25}=4R_{100}; the 25 W bulb gets 45⋅440=352\frac45\cdot440=352 V > 220 V and fuses.

Question 42

Physics · 4 marks · −1

Resistance of a given wire is obtained by measuring the current flowing in it and the voltage difference applied across it. If the percentage errors in the measurement of the current and the voltage difference are 3% each, then error in the value of resistance of the wire is

  1. A.6%
  2. B.zero
  3. C.1%
  4. D.3%

Correct answer: A

Explanation: ΔRR=ΔVV+Δii=6%\frac{\Delta R}{R}=\frac{\Delta V}V+\frac{\Delta i}i=6\%.

Question 43

Physics · 4 marks · −1

A boy can throw a stone up to a maximum height of 10 m. The maximum horizontal distance that the boy can throw the same stone up to will be

  1. A.20220\sqrt{2} m
  2. B.10 m
  3. C.10210\sqrt{2} m
  4. D.20 m

Correct answer: D

Explanation: u22g=10⇒u2g=20\frac{u^2}{2g}=10\Rightarrow\frac{u^2}{g}=20 m.

Question 44

Physics · 4 marks · −1

Statement 1: Davisson - Germer experiment established the wave nature of electrons. Statement 2: If electrons have wave nature, they can interfere and show diffraction.

  1. A.Statement 1 is false, Statement 2 is true
  2. B.Statement 1 is true, Statement 2 is false
  3. C.Statement 1 is true, Statement 2 is the correct explanation for statement 1
  4. D.Statement 1 is true, Statement 2 is true, Statement 2 is not the correct explanation for statement 1.

Correct answer: C

Explanation: The experiment observed electron diffraction from a crystal, which is what establishes wave nature.

Question 45

Physics · 4 marks · −1

A thin liquid film formed between a U-shaped wire and a light slider supports a weight of 1.5×10−21.5\times10^{-2} N (see figure). The length of the slider is 30 cm and its weight negligible. The surface tension of the liquid film is

Figure for question 45
  1. A.0.0125 Nm−1^{-1}
  2. B.0.1 Nm−1^{-1}
  3. C.0.05 Nm−1^{-1}
  4. D.0.025 Nm−1^{-1}

Correct answer: D

Explanation: Two surfaces: 2Tℓ=w⇒T=1.5×10−20.6=0.0252T\ell=w\Rightarrow T=\frac{1.5\times10^{-2}}{0.6}=0.025 N/m.

Question 46

Physics · 4 marks · −1

A charge Q is uniformly distributed over the surface of non conducting disc of radius R. The disc rotates about an axis perpendicular to its plane and passing through its centre with an angular velocity ω\omega. As a result of this rotation a magnetic field of induction B is obtained at the centre of the disc. If we keep both the amount of charge placed on the disc and its angular velocity to be constant and vary the radius of the disc then the variation of the magnetic induction at the centre of the disc will be represented by the figure

Figure for question 46
  1. A.Graph (1)
  2. B.Graph (2)
  3. C.Graph (3)
  4. D.Graph (4)

Correct answer: A

Explanation: B=μ0Qω2πR∝1RB=\frac{\mu_0Q\omega}{2\pi R}\propto\frac1R: a rectangular hyperbola.

Question 47

Physics · 4 marks · −1

Truth table for system of four NAND gates as shown in figure is

Figure for question 47
  1. A.A,B,Y: 00-0, 01-1, 10-1, 11-0
  2. B.A,B,Y: 00-0, 01-0, 10-1, 11-1
  3. C.A,B,Y: 00-1, 01-1, 10-0, 11-0
  4. D.A,B,Y: 00-1, 01-0, 10-0, 11-1

Correct answer: A

Explanation: The standard four-NAND network implements XOR: Y = 1 only when inputs differ.

Question 48

Physics · 4 marks · −1

A radar has a power of 1 Kw and is operating at a frequency of 10 GHz. It is located on a mountain top of height 500 m. The maximum distance upto which it can detect object located on the surface of the earth (Radius of earth = 6.4×1066.4\times10^6 m) is

  1. A.80 km
  2. B.16 km
  3. C.40 km
  4. D.64 km

Correct answer: A

Explanation: d=2hR=2⋅500⋅6.4×106=80d=\sqrt{2hR}=\sqrt{2\cdot500\cdot6.4\times10^6}=80 km.

Question 49

Physics · 4 marks · −1

A Carnot engine, whose efficiency is 40%, takes in heat from a source maintained at a temperature of 500 K. It is desired to have an engine of efficiency 60%. Then, the intake temperature for the same exhaust (sink) temperature must be

  1. A.efficiency of Carnot engine cannot be made larger than 50%
  2. B.1200 K
  3. C.750 K
  4. D.600 K

Correct answer: C

Explanation: Sink =300=300 K; 1−300T=0.6⇒T=7501-\frac{300}{T}=0.6\Rightarrow T=750 K.

Question 50

Physics · 4 marks · −1

If two springs S1S_1 and S2S_2 of force constants k1k_1 and k2k_2, respectively, are stretched by the same force, it is found that more work is done on spring S1S_1 than on spring S2S_2. Statement 1: If stretched by the same amount, work done on S1S_1, will be more than that on S2S_2. Statement 2: k1<k2k_1 < k_2

  1. A.Statement 1 is false, Statement 2 is true
  2. B.Statement 1 is true, Statement 2 is false
  3. C.Statement 1 is true, Statement 2 is the correct explanation for statement 1
  4. D.Statement 1 is true, Statement 2 is true, Statement 2 is not the correct explanation for statement 1.

Correct answer: A

Explanation: Same force: W=F22kW=\frac{F^2}{2k}, so W1>W2⇒k1<k2W_1>W_2\Rightarrow k_1<k_2. Same extension: W=12kx2W=\frac12kx^2, so W1<W2W_1<W_2.

Question 51

Physics · 4 marks · −1

Two cars of masses m1m_1 and m2m_2 are moving in circles of radii r1r_1 and r2r_2, respectively. Their speeds are such that they make complete circles in the same time t. The ratio of their centripetal acceleration is

  1. A.m1r1:m2r2m_1r_1 : m_2r_2
  2. B.m1:m2m_1 : m_2
  3. C.r1:r2r_1 : r_2
  4. D.1 : 1

Correct answer: C

Explanation: Same ω\omega: a=ω2r∝ra=\omega^2r\propto r.

Question 52

Physics · 4 marks · −1

A cylindrical tube, open at both ends, has a fundamental frequency, f, in air. The tube is dipped vertically in water so that half of it is in water. The fundamental frequency of the air-column is now

  1. A.f
  2. B.f2\frac{f}{2}
  3. C.3f4\frac{3f}{4}
  4. D.2f

Correct answer: A

Explanation: Closed pipe of length L2\frac L2: v4(L/2)=v2L=f\frac{v}{4(L/2)}=\frac v{2L}=f.

Question 53

Physics · 4 marks · −1

An object 2.4 m in front of a lens forms a sharp image on a film 12 cm behind the lens. A glass plate 1cm thick, of refractive index 1.50 is interposed between lens and film with its plane faces parallel to film. At what distance (from lens) should object be shifted to be in sharp focus on film?

  1. A.7.2 m
  2. B.2.4 m
  3. C.3.2 m
  4. D.5.6 m

Correct answer: D

Explanation: 1f=112+1240=780\frac1f=\frac1{12}+\frac1{240}=\frac7{80}. The slab shifts the image by 1−11.5=131-\frac1{1.5}=\frac13 cm, so the lens must image at 353\frac{35}3 cm: 1u=335−780⇒u=−560\frac1u=\frac3{35}-\frac7{80}\Rightarrow u=-560 cm.

Question 54

Physics · 4 marks · −1

A diatomic molecule is made of two masses m1m_1 and m2m_2 which are separated by a distance r. If we calculate its rotational energy by applying Bohr's rule of angular momentum quantization, its energy will be given by (n is an integer)

  1. A.(m1+m2)2n2h22m12m22r2\frac{(m_1+m_2)^2n^2h^2}{2m_1^2m_2^2r^2}
  2. B.n2h22(m1+m2)r2\frac{n^2h^2}{2(m_1+m_2)r^2}
  3. C.2n2h2(m1+m2)r2\frac{2n^2h^2}{(m_1+m_2)r^2}
  4. D.(m1+m2)n2h22m1m2r2\frac{(m_1+m_2)n^2h^2}{2m_1m_2r^2}

Correct answer: D

Explanation: I=μr2I=\mu r^2 with μ=m1m2m1+m2\mu=\frac{m_1m_2}{m_1+m_2}; E=L22I=(m1+m2)n2ℏ22m1m2r2E=\frac{L^2}{2I}=\frac{(m_1+m_2)n^2\hbar^2}{2m_1m_2r^2} (h in the options stands for ℏ\hbar).

Question 55

Physics · 4 marks · −1

A spectrometer gives the following reading when used to measure the angle of a prism. Main scale reading: 58.5 degree. Vernier scale reading: 09 divisions. Given that 1 division on main scale corresponds to 0.5 degree. Total divisions on the vernier scale is 30 and match with 29 divisions of the main scale. The angle of the prism from the above data

  1. A.58.59∘58.59^\circ
  2. B.58.77∘58.77^\circ
  3. C.58.65∘58.65^\circ
  4. D.59∘59^\circ

Correct answer: C

Explanation: LC =0.5∘30=160∘=\frac{0.5^\circ}{30}=\frac1{60}^\circ; reading =58.5+960=58.65∘=58.5+\frac9{60}=58.65^\circ.

Question 56

Physics · 4 marks · −1

An insulating solid sphere of radius R has a uniformly positive charge density ρ\rho. As a result of this uniform charge distribution there is a finite value of electric potential at the centre of the sphere, at the surface of the sphere and also at a point out side the sphere. The electric potential at infinity is zero. Statement 1: When a charge q is taken from the centre to the surface of the sphere, its potential energy changes by qρ3ϵ0\frac{q\rho}{3\epsilon_0}. Statement 2: The electric field at a distance r (r < R) from the centre of the sphere is ρr3ϵ0\frac{\rho r}{3\epsilon_0}.

  1. A.Statement 1 is true, Statement 2 is true, Statement 2 is not the correct explanation for statement 1.
  2. B.Statement 1 is true, Statement 2 is false
  3. C.Statement 1 is false, Statement 2 is true
  4. D.Statement 1 is true, Statement 2 is the correct explanation for statement 1

Correct answer: C

Explanation: Gauss's law gives E=ρr3ϵ0E=\frac{\rho r}{3\epsilon_0} (true). ΔU=q(Vs−Vc)=−qρR26ϵ0\Delta U=q(V_s-V_c)=-\frac{q\rho R^2}{6\epsilon_0}, so Statement 1 is false.

Question 57

Physics · 4 marks · −1

Proton, Deuteron and alpha particle of the same kinetic energy are moving in circular trajectories in a constant magnetic field. The radii of proton, deuteron and alpha particle are respectively rpr_p, rdr_d and rαr_\alpha. Which one of the following relations is correct?

  1. A.rα=rp=rdr_\alpha = r_p = r_d
  2. B.rα=rp<rdr_\alpha = r_p < r_d
  3. C.rα>rd>rpr_\alpha > r_d > r_p
  4. D.rα=rd>rpr_\alpha = r_d > r_p

Correct answer: B

Explanation: r∝mqr\propto\frac{\sqrt m}{q}: p 1, d 2\sqrt2, α\alpha 22=1\frac{2}{2}=1.

Question 58

Chemistry · 4 marks · −1

Which among the following will be named as dibromidobis(ethylene diamine)chromium(III) bromide ?

  1. A.[Cr(en)3]Br3[Cr(en)_3]Br_3
  2. B.[Cr(en)2Br2]Br[Cr(en)_2Br_2]Br
  3. C.[Cr(en)Br4]−[Cr(en)Br_4]^-
  4. D.[Cr(en)Br2]Br[Cr(en)Br_2]Br

Correct answer: B

Explanation: Two Br ligands, two en ligands, Cr(III), bromide counter-ion.

Question 59

Chemistry · 4 marks · −1

Which method of purification is represented by the following equation : Ti(s)+2I2(g)→523KTiI4(g)→1700KTi(s)+2I2(g)Ti(s) + 2I_2(g) \xrightarrow{523K} TiI_4(g) \xrightarrow{1700K} Ti(s) + 2I_2(g)

  1. A.zone refining
  2. B.cupellation
  3. C.Poling
  4. D.Van Arkel

Correct answer: D

Explanation: Van Arkel (iodide) process.

Question 60

Chemistry · 4 marks · −1

Lithium forms body centred cubic structure. The length of the side of its unit cell is 351 pm. Atomic radius of the lithium will be :

  1. A.75 pm
  2. B.300 pm
  3. C.240 pm
  4. D.152 pm

Correct answer: D

Explanation: r=3a4=152r=\frac{\sqrt3a}{4}=152 pm.

Question 61

Chemistry · 4 marks · −1

The molecule having smallest bond angle is :

  1. A.NCl3NCl_3
  2. B.AsCl3AsCl_3
  3. C.SbCl3SbCl_3
  4. D.PCl3PCl_3

Correct answer: C

Explanation: Bond angle falls down the group as the central atom grows: SbCl3SbCl_3.

Question 62

Chemistry · 4 marks · −1

Which of the following compounds can be detected by Molisch's test ?

  1. A.Nitro compounds
  2. B.Sugars
  3. C.Amines
  4. D.Primary alcohols

Correct answer: B

Explanation: Molisch's test (α\alpha-naphthol + conc. H2SO4H_2SO_4, violet ring) detects carbohydrates.

Question 63

Chemistry · 4 marks · −1

The incorrect expression among the following is :

  1. A.ΔGsystemΔStotal=−T\frac{\Delta G_{system}}{\Delta S_{total}} = -T
  2. B.In isothermal process wreversible=−nRTln⁡VfViw_{reversible} = -nRT\ln\frac{V_f}{V_i}
  3. C.ln⁡K=ΔH∘−TΔS∘RT\ln K = \frac{\Delta H^\circ - T\Delta S^\circ}{RT}
  4. D.K=e−ΔG∘/RTK = e^{-\Delta G^\circ/RT}

Correct answer: C

Explanation: ln⁡K=−ΔG∘RT=−ΔH∘−TΔS∘RT\ln K=-\frac{\Delta G^\circ}{RT}=-\frac{\Delta H^\circ-T\Delta S^\circ}{RT}; the sign in (3) is wrong.

Question 64

Chemistry · 4 marks · −1

The density of a solution prepared by dissolving 120 g of urea (mol. Mass = 60 u) in 1000g of water is 1.15 g/mL. The molarity of this solution is :

  1. A.0.50 M
  2. B.1.78 M
  3. C.1.02 M
  4. D.2.05 M

Correct answer: D

Explanation: Volume =11201.15=\frac{1120}{1.15} mL; M=20.974≈2.05M=\frac{2}{0.974}\approx2.05 M.

Question 65

Chemistry · 4 marks · −1

The species which can best serve as an initiator for the cationic polymerization is :

  1. A.LiAlH4LiAlH_4
  2. B.HNO3HNO_3
  3. C.AlCl3AlCl_3
  4. D.BuLi

Correct answer: C

Explanation: Lewis acids like AlCl3AlCl_3 initiate cationic polymerisation.

Question 66

Chemistry · 4 marks · −1

Which of the following on thermal decomposition yields a basic as well as an acidic oxide ?

  1. A.NaNO3NaNO_3
  2. B.KClO3KClO_3
  3. C.CaCO3CaCO_3
  4. D.NH4NO3NH_4NO_3

Correct answer: C

Explanation: CaCO3→CaOCaCO_3\rightarrow CaO (basic) +CO2+CO_2 (acidic).

Question 67

Chemistry · 4 marks · −1

The standard reduction potentials for Zn2+/ZnZn^{2+}/Zn, Ni2+/NiNi^{2+}/Ni, and Fe2+/FeFe^{2+}/Fe are −0.76-0.76, −0.23-0.23 and −0.44-0.44 V respectively. The reaction X+Y2+→X2++YX + Y^{2+} \rightarrow X^{2+} + Y will be spontaneous when :

  1. A.X = Ni, Y = Fe
  2. B.X = Ni, Y = Zn
  3. C.X = Fe, Y = Zn
  4. D.X = Zn, Y = Ni

Correct answer: D

Explanation: Need EY∘>EX∘E^\circ_Y>E^\circ_X: Zn reduces Ni2+Ni^{2+}.

Question 68

Chemistry · 4 marks · −1

According to Freundlich adsorption isotherm, which of the following is correct ?

  1. A.xm∝P0\frac{x}{m} \propto P^0
  2. B.xm∝p1\frac{x}{m} \propto p^1
  3. C.xm∝p1/n\frac{x}{m} \propto p^{1/n}
  4. D.All the above are correct for different ranges of pressure

Correct answer: D

Explanation: Low pressure: ∝p\propto p; intermediate: p1/np^{1/n}; high: p0p^0.

Question 69

Chemistry · 4 marks · −1

The equilibrium constant (KC)(K_C) for the reaction N2(g)+O2(g)→2NO(g)N_2(g) + O_2(g) \rightarrow 2NO(g) at temperature T is 4×10−44\times10^{-4}. The value of KCK_C for the reaction, NO(g)→12N2(g)+12O2(g)NO(g) \rightarrow \frac{1}{2}N_2(g) + \frac{1}{2}O_2(g) at the same temperature is :

  1. A.0.02
  2. B.2.5×1022.5\times10^2
  3. C.4×10−44\times10^{-4}
  4. D.50.0

Correct answer: D

Explanation: K′=14×10−4=50K'=\frac{1}{\sqrt{4\times10^{-4}}}=50.

Question 70

Chemistry · 4 marks · −1

The compressibility factor for a real gas at high pressure is :

  1. A.1+RT/pb1 + RT/pb
  2. B.1
  3. C.1+pb/RT1 + pb/RT
  4. D.1−pb/RT1 - pb/RT

Correct answer: C

Explanation: At high pressure the aa term is negligible: P(V−b)=RT⇒Z=1+PbRTP(V-b)=RT\Rightarrow Z=1+\frac{Pb}{RT}.

Question 71

Chemistry · 4 marks · −1

Which one of the following statements is correct ?

  1. A.All amino acids except lysine are optically active
  2. B.All amino acids are optically active
  3. C.All amino acids except glycine are optically active
  4. D.All amino acids except glutamic acid are optically active

Correct answer: C

Explanation: Glycine (H2NCH2COOHH_2NCH_2COOH) has no stereocentre.

Question 72

Chemistry · 4 marks · −1

Aspirin is known as :

  1. A.Acetyl salicylic acid
  2. B.Phenyl salicylate
  3. C.Acetyl salicylate
  4. D.Methyl salicylic acid

Correct answer: A

Explanation: Aspirin is 2-acetoxybenzoic acid (acetylsalicylic acid).

Question 73

Chemistry · 4 marks · −1

Ortho-Nitrophenol is less soluble in water than p- and m- Nitrophenols because :

  1. A.o-Nitrophenol is more volatile in steam than those of m- and p-isomers
  2. B.o-Nitrophenol shows Intramolecular H-bonding
  3. C.o-Nitrophenol shows Intermolecular H-bonding
  4. D.Melting point of o-Nitrophenol is lower than those of m- and p-isomers.

Correct answer: B

Explanation: Intramolecular H-bonding reduces H-bonding with water.

Question 74

Chemistry · 4 marks · −1

How many chiral compounds are possible on monochlorination of 2-methyl butane ?

  1. A.8
  2. B.2
  3. C.4
  4. D.6

Correct answer: B

Explanation: Products: ClCH2CH2CH(CH3)2ClCH_2CH_2CH(CH_3)_2 (achiral), CH3CHClCH(CH3)2CH_3CHClCH(CH_3)_2 (chiral), (CH3)2CClCH2CH3(CH_3)_2CClCH_2CH_3 (achiral), ClCH2CH(CH3)CH2CH3ClCH_2CH(CH_3)CH_2CH_3 (chiral): 2 chiral constitutional products.

Question 75

Chemistry · 4 marks · −1

Very pure hydrogen (99.9%) can be made by which of the following processes ?

  1. A.Reaction of methane with steam
  2. B.Mixing natural hydrocarbons of high molecular weight
  3. C.Electrolysis of water
  4. D.Reaction of salt like hydrides with water

Correct answer: C

Explanation: Electrolysis of water gives very pure hydrogen.

Question 76

Chemistry · 4 marks · −1

The electrons identified by quantum numbers n and l : (a) n = 4, l = 1 (b) n = 4, l = 0 (c) n = 3, l = 2 (d) n = 3, l = 1. Can be placed in order of increasing energy as :

  1. A.(c) < (d) < (b) < (a)
  2. B.(d) < (b) < (c) < (a)
  3. C.(b) < (d) < (a) < (c)
  4. D.(a) < (c) < (b) < (d)

Correct answer: B

Explanation: (n + l) rule: 3p (4) < 4s (4) < 3d (5) < 4p (5).

Question 77

Chemistry · 4 marks · −1

For a first order reaction, (A)→(A) \rightarrow products, the concentration of A changes from 0.1 M to 0.025 M in 40 minutes. The rate of reaction when the concentration of A is 0.01 M is :

  1. A.1.73×10−51.73\times10^{-5} M/min
  2. B.3.47×10−43.47\times10^{-4} M/min
  3. C.3.47×10−53.47\times10^{-5} M/min
  4. D.1.73×10−41.73\times10^{-4} M/min

Correct answer: B

Explanation: Two half-lives in 40 min: k=0.69320k=\frac{0.693}{20}; rate =k(0.01)=3.47×10−4=k(0.01)=3.47\times10^{-4} M/min.

Question 78

Chemistry · 4 marks · −1

Iron exhibits +2 and +3 oxidation states. Which of the following statements about iron is incorrect ?

  1. A.Ferrous oxide is more basic in nature than the ferric oxide.
  2. B.Ferrous compounds are relatively more ionic than the corresponding ferric compounds
  3. C.Ferrous compounds are less volatile than the corresponding ferric compounds.
  4. D.Ferrous compounds are more easily hydrolysed than the corresponding ferric compounds.

Correct answer: D

Explanation: The more highly charged Fe3+Fe^{3+} compounds hydrolyse more readily.

Question 79

Chemistry · 4 marks · −1

The pH of a 0.1 molar solution of the acid HQ is 3. The value of the ionization constant, Ka of this acid is :

  1. A.3×10−13\times10^{-1}
  2. B.1×10−31\times10^{-3}
  3. C.1×10−51\times10^{-5}
  4. D.1×10−71\times10^{-7}

Correct answer: C

Explanation: Ka=(10−3)20.1=10−5K_a=\frac{(10^{-3})^2}{0.1}=10^{-5}.

Question 80

Chemistry · 4 marks · −1

Which branched chain isomer of the hydrocarbon with molecular mass 72u gives only one isomer of mono substituted alkyl halide ?

  1. A.Tertiary butyl chloride
  2. B.Neopentane
  3. C.Isohexane
  4. D.Neohexane

Correct answer: B

Explanation: C5H12C_5H_{12}; neopentane has only equivalent hydrogens.

Question 81

Chemistry · 4 marks · −1

KfK_f for water is 1.86K kg mol−1^{-1}. If your automobile radiator holds 1.0 kg of water, how many grams of ethylene glycol (C2H6O2)(C_2H_6O_2) must you add to get the freezing point of the solution lowered to −2.8∘-2.8^\circC ?

  1. A.72g
  2. B.93g
  3. C.39g
  4. D.27g

Correct answer: B

Explanation: m=2.81.86=1.505m=\frac{2.8}{1.86}=1.505 mol/kg; mass =1.505⋅62≈93=1.505\cdot62\approx93 g.

Question 82

Chemistry · 4 marks · −1

What is DDT among the following :

  1. A.Greenhouse gas
  2. B.A fertilizer
  3. C.Biodegradable pollutant
  4. D.Non-biodegradable pollutant

Correct answer: D

Explanation: DDT is a persistent, non-biodegradable pesticide.

Question 83

Chemistry · 4 marks · −1

The increasing order of the ionic radii of the given isoelectronic species is :

  1. A.Cl−,Ca2+,K+,S2−Cl^-, Ca^{2+}, K^+, S^{2-}
  2. B.S2−,Cl−,Ca2+,K+S^{2-}, Cl^-, Ca^{2+}, K^+
  3. C.Ca2+,K+,Cl−,S2−Ca^{2+}, K^+, Cl^-, S^{2-}
  4. D.K+,S2−,Ca2+,Cl−K^+, S^{2-}, Ca^{2+}, Cl^-

Correct answer: C

Explanation: For isoelectronic ions radius increases as nuclear charge decreases.

Question 84

Chemistry · 4 marks · −1

2-Hexyne gives trans-2-Hexene on treatment with :

  1. A.Pt/H2Pt/H_2
  2. B.Li/NH3Li/NH_3
  3. C.Pd/BaSO4Pd/BaSO_4
  4. D.LiAlH4LiAlH_4

Correct answer: B

Explanation: Dissolving-metal reduction gives trans-alkenes.

Question 85

Chemistry · 4 marks · −1

Iodoform can be prepared from all except :

  1. A.Ethyl methyl ketone
  2. B.Isopropyl alcohol
  3. C.3-Methyl-2-butanone
  4. D.Isobutyl alcohol

Correct answer: D

Explanation: Isobutyl alcohol (CH3)2CHCH2OH(CH_3)_2CHCH_2OH lacks the CH3CO−CH_3CO- / CH3CH(OH)−CH_3CH(OH)- unit.

Question 86

Chemistry · 4 marks · −1

In which of the following pairs the two species are not isostructural ?

  1. A.CO32−CO_3^{2-} and NO3−NO_3^-
  2. B.PCl4+PCl_4^+ and SiCl4SiCl_4
  3. C.PF5PF_5 and BrF5BrF_5
  4. D.AlF63−AlF_6^{3-} and SF6SF_6

Correct answer: C

Explanation: PF5PF_5 is trigonal bipyramidal; BrF5BrF_5 is square pyramidal.

Question 87

Chemistry · 4 marks · −1

In the given transformation, which of the following is the most appropriate reagent ? 4-(3-oxobut-1-enyl)cyclohexan-1-ol (HO−C6H10−CH=CHCOCH3HO-C_6H_{10}-CH=CHCOCH_3) →\rightarrow HO−C6H10−CH=CHCH2CH3HO-C_6H_{10}-CH=CHCH_2CH_3

Figure for question 87
  1. A.NH2NH2NH_2NH_2, OH−OH^-
  2. B.Zn-Hg/HCl
  3. C.Na, Liq. NH3NH_3
  4. D.NaBH4NaBH_4

Correct answer: A

Explanation: Wolff-Kishner reduces C=O to CH2CH_2 without touching the OH or the C=C; Clemmensen's acid would affect the alcohol, and the others give alcohols.

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