MCQs on Law of Mass Action

MCQs on Law of Mass Action

1. Which of the following is not correct?

1. the rate law is an experimental fact, but the law of mass action is theoretical
2. the rate law is always different from the expression of the law of mass action
3. the rate law is more informative than the law of mass action for the development of a mechanism
4. the order of a reaction is equal to the sum of the powers of the concentration terms in the rate law.

Answer: (b)

2. The temperature coefficient of a reaction is 2. How many times the rate of reaction increases when the temperature is increased from 30^oC to 60^oC.

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

Answer: (c)

3. If a reaction with t_1/2 = 69.3 sec, has a rate constant 10^-2 per sec the order is

1. zero
2. 1
3. 2
4. 3

Answer: (b)

4. K for a zero-order reaction is 2 x 10^-2 mole/L/sec. If the concentration of reactant after 25 sec is 0.5M, the initial concentration must have been

1. 0.5M
2. 1.25M
3. 12.5M
4. 1.0M

Answer: (d)

5. A first-order reaction is 75% complete after 32 minutes. When was 50% of the reaction completed?

1. 16min
2. 8min
3. 4min
4. 32min

Answer: (a)

6. What is the half-life of a radioactive substance if 87.5% of any given amount of the substance disintegrate in 40 minutes?

1. 160 min
2. 10 min
3. 20 min
4. 13 min 20 sec

Answer: (d)

7. Half-life of 10g of radioactive substance is 10 days. The half-life of 20 g is

1. 10 days
2. 5 days
3. 20 days
4. 40 days

Answer: (a)

8. The chemical reactions in which reactants need a high amount of activation energy are generally

1. fast
2. slow
3. very fast
4. instantaneous

Answer: (b)

9. For a reaction A → Products the rate of reaction doubles when the concentration of A is increased by 4 times. The order of the reaction is

1. 4
2. 0
3. 1/2
4. 1

Answer: (c)

10. The number of atoms or molecules whose concentration alters during a chemical change is its

1. molecularity
2. order of reaction
3. change in reaction
4. none

Answer: (b)