Chemical Kinetics Mock Test – Class 12 Chemistry

1. Consider the following statements about calculating the average disappearance rate of a reactant.
Statement I: .
Statement II: .
Statement III: A negative sign is placed before .
The valid statements are:

2. Consider the following statements about the effect of reactant concentration on rate.
Statement I: Doubling a reactant concentration doubles the rate only when the reaction is first order with respect to that reactant.
Statement II: A zero-order rate is independent of reactant concentration within the range where zero-order behaviour applies.
Statement III: The concentration effect must be obtained from the rate law of the reaction.
The valid statements are:

3. Chemical kinetics is primarily concerned with:

4. Match each expression in Column I with its sign interpretation in Column II.

5. The progress of a reaction is monitored through the concentration of reactant . The average disappearance rates over successively shorter intervals around are shown below.

The best estimate of the instantaneous disappearance rate at is:

6. A reactant concentration becomes zero because that reactant has been completely exhausted in an irreversible reaction mixture. The forward rate must then:

7. For the same reaction at the same temperature, the activation energies normally satisfy:

8. For a gaseous reaction obeying at fixed temperature, a graph of rate against should be:

9. A short portion of a concentration-time curve appears nearly straight. Which additional evidence would most strongly support a claimed kinetic order?

10. For first-order decomposition

starting with pure at pressure , the appropriate pressure-based rate equation is:

11. Assertion: A single concentration measurement at one non-zero time is usually insufficient to establish reaction order.
Reason: Different integrated rate laws can often be fitted to one initial and one later concentration by choosing different values of .

12. The kinetic law applies to a reaction. In one experiment, when and . At the same temperature, is changed to and to . The new rate is:

13. After four half-lives of a first-order reaction, the fraction of reactant remaining is:

14. A catalyst changes the rate constant of a reaction from to at the same temperature. The catalytic rate-constant enhancement factor is:

15. Two points on an Arrhenius plot are given below.

The activation energy is closest to:

16. Increasing by a factor of increases the initial rate by a factor of , while all other variables remain unchanged. The partial order with respect to is:

17. In the reaction , the raw rate of appearance of is generally:

18. An ionic precipitation reaction in aqueous solution is often faster than a reaction requiring extensive covalent-bond rearrangement because:

19. The rate expression for contains a missing factor.

20. At , a reaction has and . Its rate constant at is closest to:

21. Two samples P and Q undergo the same first-order reaction at the same temperature for the same time. Their initial concentrations are and , respectively. Which statement is correct?

22. During a reaction at fixed temperature and with no change in catalyst condition, reactant concentrations decrease and the measured rate becomes smaller. The rate constant generally:

23. Which elementary step is termolecular?

24. During the reaction , a concentration-time graph gives a tangent slope of for at a particular instant. At the same instant, the slope for and the normalised reaction rate are:

25. The collision-theory expression for a rate constant is commonly written as:

26. A graph of rate against bends upward, whereas a graph of rate against is a straight line through the origin. Which concentration change will multiply the rate by ?

27. Assertion: The pre-exponential factor has the same units as the rate constant .
Reason: The exponential factor is dimensionless.

28. Catalytic-surface kinetics are studied using the following observations.

Which interpretation is best supported over the tested range?

29. On a reaction-coordinate energy profile, the forward activation energy is represented by:

30. When , the slope of a plot of against is:

31. For a zero-order reaction involving reactant , the differential rate law is:

32. The measured half-life of a first-order reaction is . Its rate constant is:

33. The sampling method is evaluated using the statements below.
Statement I: Samples should be taken at known times.
Statement II: Removal of samples should be small enough not to disturb the remaining mixture significantly.
Statement III: The reaction in each sample may need to be quenched before analysis.
The valid statements are:

34. When the temperature of a reacting system is raised while concentrations and other conditions are kept unchanged, the reaction rate generally:

35. On a molecular-energy distribution graph, the fraction of molecules having energy sufficient for reaction is represented by:

36. Assertion: The unit of for a pseudo-first-order reaction is .
Reason: After the excess-reactant factor is absorbed into , the observed law has the form .

37. The rate law is . The unit of is:

38. Consider the following statements about the average rate of appearance of a product.
Statement I: is positive when the product concentration increases.
Statement II: The expression does not require a leading negative sign.
Statement III: Adding a negative sign would make the reported value negative for normal product formation.
The valid statements are:

39. Two reactions have rate constants with numerical values and , but their overall orders are different. Which conclusion is justified from these numerical values alone?

40. A reaction mixture contains one strongly coloured reactant, while all other reactants and products are nearly colourless at the selected wavelength. Continuous absorbance measurement is especially suitable because:

41. Concentration-time data for a reaction are shown below.

If the reaction is zero order, the graph parameters are:

42. A concentration-time graph is to be drawn for a reacting species. The conventional placement of variables is:

43. Assertion: The rate of a typical concentration-dependent reaction often decreases as the reaction proceeds.
Reason: Reactant concentrations generally fall during forward reaction progress.

44. Rate constants of a reaction are at and at . The activation energy is closest to:

45. When a reaction's products lie below the reactants on an energy profile:

46. A reaction has and . The enthalpy change for the forward reaction is:

47. Absorbance is proportional to the concentration of a first-order reactant. The slopes of -versus- plots are at and at . The activation energy is closest to:

48. A surface reaction is zero order in reactant while the catalyst surface is saturated. When becomes very small, the rate begins to decrease with . This observation shows that:

49. Consider the following statements about basic kinetic notation.
Statement I: commonly represents time.
Statement II: commonly represents reactant concentration.
Statement III: commonly represents the rate constant.
The valid statements are:

50. At a certain temperature, . The approximate fraction of collisions energetic enough to overcome the barrier is: