NCERT Chemistry Class 12 Chemical Kinetics - Chapter 4 Quiz 1

1. For a chemical reaction, X + 2Y → Z, if the rate of appearance of Z is 0.50 moles per liter per hour, then the rate of disappearance of Y is:

0.5 mol L⁻¹ hr⁻¹

1.0 mol L⁻¹ hr⁻¹

0.25 mol L⁻¹ hr⁻¹

Cannot be predicted

2. For the reaction, NO₂(g) + CO(g) → NO(g), the correct expression for the rate of the reaction is:

rate = −d[NO₂]/dt

rate = −d[CO₂]/dt

rate = d[NO₂] − d[CO]/dt

rate = d[CO₂]/dt

3. The rate of a reaction is primarily determined by the slowest step. This step is called:

Rate-determining step

Activation step

Reaction rate step

None of these

4. The reaction of high molecularity is rare because:

Many-body collisions have a low probability

Many-body collisions are not favored energetically

Activation energy of many-body collisions is very large

Very high concentration is required for such reactions

5. For a chemical reaction A → B, it is found that the rate of the reaction quadruples when the concentration of A is doubled. The rate expression for the reaction is

rate = k[A]

rate = k[A]²

rate = k

rate = k[A]³

6. On increasing the temperature of the reacting system by 10°C, the rate of reaction almost becomes double. The most appropriate reason for this is that

Activation energy decreases with an increase in temperature

The fraction of molecules having threshold energy increases

Collision frequency increases

The value of threshold energy decreases

7. The half-life period of any first-order reaction

Is half the specific rate constant

Is always the same irrespective of the reaction

Is independent of initial concentration

Is directly proportional to the initial concentration of reactants

8. The dimensions of the rate constant of a second-order reaction involve

Concentration

Concentration and time

Time only

Neither time nor concentration

9. A zero-order reaction A → Products has a rate constant of 10⁻² mol L⁻¹ s⁻¹. If a process is started with 10 moles of A in a one-liter vessel, the number of moles of reactant after 10 minutes will be

10

5

6

4

10. For which of the following reactions, the temperature coefficient is maximum?

A → B: Eₐ = 50 kJ

P → Q: Eₐ = 40 kJ

X → Y: Eₐ = 60 kJ

W → Z: Eₐ = 80 kJ

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