Chemical Kinetics Mock Test – Class 12 Chemistry

1. Consider the following statements for a reaction progressing in the forward direction.
Statement I: Reactant concentrations generally decrease with time.
Statement II: Product concentrations generally increase with time.
Statement III: The stoichiometric coefficients help relate the amounts of different species consumed and formed.
The valid statements are:

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

3. For an overall reaction order , the general unit of the rate constant , when concentration is expressed in and time in seconds, is:

4. The exponential form of the first-order integrated rate equation is:

5. A differential rate equation and an integrated rate equation differ mainly because:

6. Assertion: Reaction order may change when the reaction conditions or dominant mechanism change.
Reason: Molecularity of a specified elementary step can take fractional values under different conditions.

7. Initial-rate data for a reaction involving and are:

The correct rate law, value of , and predicted rate at and are:

8. For the true rate law , one experiment uses approximately times . Which interpretation is most suitable?

9. The first-order rate constant is . The time required for only of the reactant to remain is closest to:

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

11. A proposed rate law is used to calculate from four independent initial-rate experiments. The values obtained are shown below.

All experiments were performed at the same temperature and catalyst condition. The most suitable conclusion is:

12. The instantaneous rate of disappearance of reactant is written as:

13. A reaction obeys . Which unit belongs to ?

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

15. Two samples undergo the same first-order reaction at the same temperature. Sample P begins with , and Sample Q begins with . After the same elapsed time, of Sample P remains. The amount of Sample Q remaining is:

16. A reaction obeys , where . Its initial rate when and is:

17. The following half-life data are obtained for one reaction.

The reaction order and rate constant are:

18. 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:

19. An energy profile has and . The reverse activation energy is:

20. The concentration of a species rises from to during a recorded interval. Applying gives a negative value. The best interpretation is:

21. A surface-catalysed reaction is zero order in gaseous while all active sites are saturated. As becomes very small, the -versus- graph begins to bend away from its original straight line. The most likely explanation is:

22. The following pressure data are obtained for , starting with pure .

The first-order rate constant calculated from the data is closest to:

23. Two reactions have the same collision frequency and activation energy at the same temperature. Their steric factors are and . The ratio of their rate constants is:

24. The reaction between and is studied at constant temperature. Doubling while keeping fixed doubles the initial rate. Doubling while keeping fixed quadruples the initial rate. The supported differential rate law is:

25. The measured half-life of a zero-order reaction is . The time required for the reactant concentration to decrease from to is:

26. Arrhenius-plot data for three reactions are shown below.

The order of activation energies is:

27. A solution contains of reactant in . Without changing the amount of reactant, the solution is concentrated to a final volume of . The final concentration is:

28. For the true rate law

when is isolated by using it in large excess, the observed rate constant is:

29. On a graph of against time for a first-order reaction, the vertical decrease during one half-life is:

30. Which role of a balanced chemical equation is most relevant as a prerequisite for studying reaction rates?

31. For the constant-volume reaction , the overall reaction rate is . Select the internally consistent row.

32. Absorbance, which is proportional to reactant concentration, is used to monitor a first-order reaction.

The predicted absorbance at is closest to:

33. A catalyst participates in intermediate steps of a reaction mechanism but is absent from the overall balanced equation because:

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

Which interpretation is best supported over the tested range?

35. The missing factor in the average rate-of-disappearance expression is ______.

36. The vertical intercept of a plot of against is . The pre-exponential factor is:

37. A complex reaction differs from an elementary reaction because a complex reaction:

38. The following mechanism is proposed:


The overall equation and predicted simple rate law are:

39. Assertion: For the constant-volume reaction , the magnitude of the average rate of disappearance of equals the average rate of appearance of .
Reason: The stoichiometric coefficients of and are both unity.

40. Zero-order disappearance begins with of a reactant and has . The idealised completion time is:

41. A rate value is reported as for a second-order reaction. A claim states that the unit must instead be . The claim confuses:

42. Molecularity of an elementary step is defined as:

43. Raising the external gas pressure has no necessary direct effect on the rate of a reaction occurring only between dissolved non-gaseous reactants because:

44. When doubling increases the reaction rate by a factor of , the order with respect to is ______.

45. A catalyst is added to a reaction mixture without changing its temperature. On a molecular-energy distribution graph, the immediate effect is best represented by:

46. A reversible reaction is allowed to proceed in two identical closed vessels at the same temperature. A catalyst is added only to Vessel P. Compared with Vessel Q, Vessel P will:

47. Equal masses of calcium carbonate are used in two experiments with the same acid concentration and temperature. Experiment P uses one large marble chip, while Experiment Q uses finely powdered calcium carbonate. Experiment Q is expected to react faster mainly because it has:

48. A photochemical reaction proceeds under constant absorbed light intensity. Its rate remains unchanged when the reactant concentration is moderately increased. The observation is consistent with zero-order behaviour because:

49. Reaction-coordinate profiles are assessed through the statements below.
Statement I: The horizontal axis represents progress along a reaction pathway, not ordinary elapsed time.
Statement II: The vertical axis commonly represents potential energy or enthalpy.
Statement III: The width of a peak directly gives the numerical reaction time.
The valid statements are:

50. The integrated rate equation for a zero-order disappearance of is: