Chemical Kinetics Mock Test – Class 12 Chemistry

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

2. For the elementary step

the rate law is most reasonably written as:

3. A reaction has a high collision frequency, but its rate constant is still small. Which explanation is most appropriate?

4. Initial-rate results for a reaction are shown below.

The rate law and rate constant are:

5. Complete the collision-theory relation.

6. A researcher already knows the instantaneous law

but needs an equation containing , , and . The next required mathematical step is to:

7. A student is told that of a first-order reactant has decomposed and substitutes for . The correct remaining fraction is:

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

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

10. In , the final pressure is . The total pressures at , , and are , , and , respectively. Which conclusion is supported?

11. The proportionality

is converted into an equality by introducing:

12. A rate law determined for a reaction at in the absence of a catalyst should be applied directly to another experiment only when:

13. The pressure method can be used to follow a gaseous reaction at constant temperature and volume because:

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

15. Which combination is impossible?

16. The rate law is . If is doubled while is reduced to one-half of its original value at constant temperature, the new rate is:

17. Activation energy is described through the following statements.
Statement I: It represents an energy barrier that reacting species must overcome.
Statement II: It is necessarily equal to the enthalpy change of reaction.
Statement III: It is commonly expressed in .
The valid statements are:

18. 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:

19. 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:

20. Evaluate the three statements about stoichiometrically normalised rate.
Statement I: Such normalised rate expressions are commonly applied under constant-volume conditions.
Statement II: At constant volume, concentration changes are directly proportional to changes in molar amounts.
Statement III: If volume changes substantially, concentration may change for reasons other than chemical consumption or formation.
The valid statements are:

21. Match each overall reaction order in Column I with the corresponding unit of in Column II.

22. The absorbance of a solution is directly proportional to the concentration of a first-order reactant. Absorbance falls from to in . The first-order rate constant is closest to:

23. 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:

24. An uncatalysed reaction has and . A catalyst lowers the forward activation energy to . For the same overall reaction, the catalysed reverse activation energy is:

25. In a hydrolysis experiment, water is present in such large excess that its concentration is effectively constant. If the true rate law is , the observed law is:

26. For the general stoichiometric equation , the stoichiometrically normalised reaction rate is represented by:

27. 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.

28. 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:

29. Definite integration of a first-order law from at to at time gives:

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

31. For reaction , the instantaneous rate of appearance of is . The instantaneous rate of disappearance of is:

32. Reaction P has both a larger pre-exponential factor and a larger activation energy than Reaction Q. Their Arrhenius lines intersect at temperature . Which comparison is correct?

33. On a graph of reactant concentration against time, a straight secant line joins the points corresponding to and . The average rate of disappearance over this interval equals:

34. Integrated rate equations are assessed through the statements below.
Statement I: Their mathematical form depends on the reaction order.
Statement II: They are derived under conditions for which is treated as constant.
Statement III: The same concentration-time equation applies to every reaction order.
The valid statements are:

35. Two pseudo-first-order runs use the true rate law at the same temperature. Run P keeps nearly constant at , whereas Run Q keeps it at . Which statement is valid?

36. Which description best represents a graph of against absolute temperature for an ordinary reaction with positive activation energy?

37. The energy relations for a reaction are:

The forward activation energy and reaction enthalpy are:

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

39. 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:

40. 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:

41. Match each reaction feature in Column I with the most suitable monitoring method in Column II.

42. The correct variable-separation step for

is:

43. For zero-order disappearance, and . The concentration after is:

44. Reaction order is assessed through the statements below.
Statement I: An overall order may be zero.
Statement II: An overall order may be fractional.
Statement III: Every overall reaction must have a positive whole-number order.
The valid statements are:

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

46. A reactant undergoing zero-order disappearance loses during each interval. Which interpretation is supported?

47. The Arrhenius equation is:

48. The correct two-temperature Arrhenius relation is:

49. 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:

50. A reaction has a temperature coefficient of . Its rate at is . Assuming the coefficient remains valid, the rate at is: