Chemical Kinetics Mock Test – Class 12 Chemistry

1. Which statement best describes reaction order?

2. Match each elementary step in Column I with its molecularity description in Column II.

3. During an interval, a reactant concentration decreases from to . Its average rate of disappearance is:

4. Assertion: Increasing a reactant concentration does not always increase the reaction rate.
Reason: A reaction may be zero order with respect to that reactant under the stated conditions.

5. Which observation is not explained adequately by the simplest collision theory alone?

6. Which combination is impossible?

7. Experimental data give a straight line for against , while the -against- plot shows systematic curvature. Its half-life also doubles when doubles. The reaction is:

8. In a constant-volume vessel, the reaction causes the concentration of to decrease from to . Assuming no product was initially present, the concentration of formed is:

9. The first-order half-life expression is:

10. For an Arrhenius plot of against , the slope and vertical intercept are:

11. Which feature may appear on a catalysed energy profile even when the uncatalysed profile has only one peak?

12. Assertion: The integrated first-order rate equation contains a logarithm of concentration.
Reason: Integration of gives .

13. A reaction is monitored for . The concentration changes slowly during the first , rapidly during the next , and then slowly again. A single rate calculated from the initial and final concentrations represents:

14. A graph of rate constant on the vertical axis against temperature on the horizontal axis rises more steeply at higher temperatures. The graph supports the conclusion that:

15. The initial rate of a reaction is best described as:

16. At , a reaction has and . The rate constant at is closest to:

17. Assertion: Successive half-lives of an ideal first-order reaction are equal at fixed temperature.
Reason: The same fraction of the reactant is consumed during each equal half-life interval.

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

19. A first-order reaction is complete in at . Its activation energy is . The time for completion at is closest to:

20. A reactant curve and a product curve are examined at the same time for the reaction . The tangent to the reactant curve has slope . The tangent to the product curve should have slope:

21. A reaction is tested by plotting concentration data in two ways. The plot of against is curved, but the plot of against is a straight line with a negative slope. The most suitable conclusion is:

22. For a forward reaction monitored from its initial mixture, the usual concentration trends are:

23. The rate factors caused by doubling the concentration of a reactant are arranged for four partial orders. Which sequence is correct for orders , , , and , respectively?

24. Starting with

which sequence correctly leads to the zero-order integrated rate equation?

25. Absorbance readings for a coloured reactant are shown below. Under the measurement conditions, absorbance is directly proportional to its concentration.

The data indicate that:

26. The rate is expressed as . Its unit indicates:

27. 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:

28. Assertion: The number of total collisions in a reacting system is generally much larger than the number of effective collisions.
Reason: Many collisions have insufficient energy or unsuitable orientation.

29. 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:

30. A common-log plot of against time has slope . The value of and the percentage remaining after are closest to:

31. 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:

32. When first-order disappearance gives , the expression that produces a positive value of is:

33. Dividing a species-based rate by its stoichiometric coefficient is necessary because:

34. A report applies the rule “the rate doubles for every increase” to all reactions from to . The main weakness in this reasoning is that:

35. At , a reaction has . The fraction is closest to:

36. A reaction is monitored through the concentration of product . To estimate the rate at exactly , a tangent is drawn at the corresponding point of the -versus- curve. The tangent passes through and . The rate at is:

37. Assertion: Collision theory is more successful qualitatively than quantitatively for many complex reactions.
Reason: Real molecules may have complicated energy redistribution, intermolecular forces, and multistep pathways.

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

Which interpretation is best supported over the tested range?

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

40. When all reactant concentrations in a rate law are doubled simultaneously and the initial rate becomes eight times larger, the safest conclusion is:

41. A tangent is drawn to a product concentration-time curve at . Two convenient points on the tangent are and . The instantaneous rate of appearance at is:

42. A mechanism contains a fast step followed by the slow elementary step . Why is not usually accepted as the final overall rate law?

43. A reacting gas mixture is compressed while the reaction proceeds, and the measured concentration of reactant increases slightly despite its consumption. Why can not be interpreted directly as the reaction rate?

44. A straight-line plot of against has slope and intercept . The concentration after is closest to:

45. A normalised molecular-energy distribution curve has molecular energy on the horizontal axis and a total area of . A vertical line marks the activation energy . The area beneath the curve to the right of this line represents:

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

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

48. For , the concentration changes over a fixed interval satisfy:

This relation implies that:

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

50. At a chosen time in the reaction , the tangent to the -versus- curve has slope . The tangent slope of the -versus- curve at that time is: