The half-lives of two radioactive nuclides A and B are 1 and 2 mi

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 Multiple Choice QuestionsMultiple Choice Questions

121.

Consider the folowing reaction,

A → Products

This reaction is completed in 100 mins. The rate constant of this reaction at t1 = 10 min is 10-2 min-1. What is the rate constant (in min-1) at t2 = 20 min.

  • 2 × 10-2

  • 10-2

  • 5 × 10-3

  • 0.1


122.

Consider the following reaction,

N2(g) + 3H2(g) → 2NH3(g)

The rate of this reaction in terms of N2 at T K is -d [N2]dt = 0.02 mol L-1s-1. What is the value of -d[H2]/ dt (in units of mol L-1s-1) at the same temperature.

  • 0.02

  • 50

  • 0.06

  • 0.04


123.

10 g of a radioactive element is disintegrated to 1 g in 2.303 minutes.What is the half-life (in minutes) of that radioactive element?

  • 1/ 0.693

  • 6.93

  • 1

  • 0.693


124.

Which one of the following equation is correct for the reaction?

 N2(g) + 3H2(g) → 2NH3 (g)?

  • 3d[NH3]dt=2d[H2]dt

  • 3d[NH3]dt=3d[H2]dt

  • 2d[NH3]dt= -3d[H2]dt

  • 3d[NH3]dt= -2d[H2]dt


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125.

......... of a reaction cannot be determined experimentally.

  • Order

  • Rate

  • Rate constant

  • Molecularity


126.

Assertion (A) - At 300 K, kinetic energy of 16 g of methane is equal to the kinetic energy of 32 g of oxygen.

Reason (R) - At constant temperature, kinetic energy of one mole of all gases is equal.

The correct answer is 

  • Both (A) and (R) are true and (R) is the correct explanation of (A)

  • Both (A) and (R) are true but (R) is not the correct explanation of (A).

  • (A) is true but (R) is not true.

  • (A) is not true but (R) is true


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127.

The half-lives of two radioactive nuclides A and B are 1 and 2 min respectively. Equal weights of A and B are taken separately and allowed to disintegrate for 4min. What will be the ratio of weights of A and B disintegrated?

  • 1:2

  • 5:4

  • 1:2

  • 1:3


B.

5:4

For, A t1/2 = 1min

∴  part of A remained after 4 minutes.

 (i.e, 4 half- life) will be = 1/16

∴ part of A disintegrated in the same period = 15/16

For B, t1/2 = 2mm

∴ Part of B remained after 4min (i.e., 2 half life) = 1/4

∴ part of B disintegrated in the same time = 3/4

Hence, ratio of disintergrated weight of A and B

  = 1516:34= 15:12 = 5:4


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128.

Observe the following reaction 2A + B → C. The rate of formation of C is 2.2 × 10-3 mol L-1min-1. What is the value of - d[A]dt (in mol L-1min-1)?

  • 2.2 × 10-3 

  • 1.1 × 10-3 

  • 4.4 × 10-3 

  • 5.5  × 10-3 


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129.

The rate constant of a first order reaction at 27°C is 10-3 min-1. The temperature coefficient of this reaction is 2. What is the rate constant (in min-1 ) at 17°C for this reaction ?

  • 10-3

  • 5 × 10-4

  • 2 × 10-3

  • 10-2


130.

What is the temperature at which the kinetic energy of 0.3 moles of helium is equal to the kinetic energy of 0.4 moles of argon at 400 K?

  • 400 K

  • 873 K

  • 533 K

  • 300 K


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