Reaction Rates - AP Chemistry

1. Identify the rate-determining step in a reaction mechanism.

   The slowest step in the mechanism. Controls overall reaction rate.

2. How do you experimentally determine the rate law of a reaction?

   Using the method of initial rates. Measure initial rates at different concentrations.

3. Define rate constant in the context of reaction rates.

   The proportionality constant (k) in the rate law. Units depend on reaction order.

4. What is the effect of increasing concentration on reaction rate?

   Increases the reaction rate. More reactant molecules available for collision.

5. What is the role of intermediates in a reaction mechanism?

   Species that appear in the mechanism but not in the overall equation. Formed and consumed during reaction pathway.

6. What is the typical unit for reaction rate?

   Molarity per second (M/s). Change in concentration per unit time.

7. What is the half-life formula for a first-order reaction?

   $t_{1/2} = \frac{0.693}{k}$. Time for concentration to drop to half initial value.

8. Which factors influence the activation energy of a reaction?

   Nature of reactants and presence of a catalyst. Intrinsic properties determine energy barrier height.

9. What does the term 'molecularity' refer to?

   The number of molecules involved in an elementary step. Can be 1, 2, or 3 for elementary reactions.

10. What is the relationship between temperature and the rate constant?

    Rate constant increases with temperature. Exponential relationship from Arrhenius equation.

11. State the Arrhenius equation.

    $k = Ae^{-E_a/RT}$. Relates rate constant to temperature and activation energy.

12. Identify the rate-determining step in a reaction mechanism.

    The slowest step in the mechanism. Controls overall reaction rate.

13. How does a catalyst affect the activation energy of a reaction?

    Lowers the activation energy. Provides alternative pathway with lower energy barrier.

14. What is the integrated rate law for a first-order reaction?

    [A] = [A]_0 $e^{-kt}$. Shows exponential decay of concentration.

15. How does surface area affect the rate of a heterogeneous reaction?

    Increasing surface area increases the rate. More contact area means more collision sites.

16. What is the effect of temperature on the activation energy?

    No effect; activation energy is constant. Activation energy is an intrinsic property.

17. What does the term 'reaction mechanism' refer to?

    The step-by-step sequence of elementary reactions. Shows how overall reaction occurs at molecular level.

18. What is the relationship between temperature and the rate constant?

    Rate constant increases with temperature. Exponential relationship from Arrhenius equation.

19. What is the effect of temperature on the activation energy?

    No effect; activation energy is constant. Activation energy is an intrinsic property.

20. How do you experimentally determine the rate law of a reaction?

    Using the method of initial rates. Measure initial rates at different concentrations.

21. What is the physical significance of the rate constant (k)?

    Indicates speed of reaction at a given temperature. Larger k means faster reaction at same conditions.

22. What is the collision theory of reaction rates?

    Reactions occur when particles collide with sufficient energy. Effective collisions have proper orientation and energy.

23. How do you experimentally determine the rate law of a reaction?

    Using the method of initial rates. Measure initial rates at different concentrations.

24. How can the order of a reaction be determined experimentally?

    By measuring how rate changes with concentration. Compare rates at different concentrations.

25. Which factor does not affect the rate constant?

    Concentration of reactants. Rate constant only depends on temperature and catalyst.

26. What is the typical effect of a catalyst on reaction equilibrium?

    No effect on equilibrium position. Speeds both forward and reverse reactions equally.

27. What is the unit of the rate constant for a zero-order reaction?

    M/s. Rate is independent of concentration.

28. Identify the units of the rate constant for a second-order reaction.

    $M^{-1}$ $s^{-1}$. Units are $M^{1-n}s^{-1}$ where n is overall order.

29. What is the effect of a catalyst on the rate constant?

    Increases the rate constant. Provides lower activation energy pathway.

30. How do you determine the overall order of a reaction?

    Sum the exponents of all reactants in the rate law. Add all concentration exponents in rate law.

31. Identify the unit of the rate constant for a third-order reaction.

    $M^{-2} s^{-1}$. Pattern: $M^{1-n}s^{-1}$ where n=3.

32. Identify the rate-determining step in a reaction mechanism.

    The slowest step in the mechanism. Controls overall reaction rate.

33. What is the typical effect of a catalyst on reaction equilibrium?

    No effect on equilibrium position. Speeds both forward and reverse reactions equally.

34. Which graph is linear for a first-order reaction?

    ln[A] vs. time. Integrated rate law form for first-order kinetics.

35. Identify the unit of the rate constant for a third-order reaction.

    $M^{-2}$ $s^{-1}$. Pattern: $M^{1-n}s^{-1}$ where n=3.

36. Identify the order of reaction if rate = k[A]^0[B]^1.

    First order with respect to B. Zero order in A, first order in B.

37. What is the relationship between reaction rate and concentration for a zero-order reaction?

    Rate is independent of concentration. Constant rate regardless of concentration changes.

38. Define activation energy.

    The minimum energy required to initiate a reaction. Energy barrier that must be overcome.

39. What affects the frequency factor (A) in the Arrhenius equation?

    Orientation and frequency of collisions. Pre-exponential factor in Arrhenius equation.

40. What is the formula for the rate law of a reaction?

    Rate = k[A]^m[B]^n. Where m and n are orders determined experimentally.

41. What is the effect of pressure on the rate of a gaseous reaction?

    Increasing pressure increases the rate. Higher pressure increases concentration of gases.

42. What is the effect of pressure on the rate of a gaseous reaction?

    Increasing pressure increases the rate. Higher pressure increases concentration of gases.

43. What is the typical effect of a catalyst on reaction equilibrium?

    No effect on equilibrium position. Speeds both forward and reverse reactions equally.

44. State the expression for the half-life of a zero-order reaction.

    $t_{1/2} = \frac{[A]_0}{2k}$. Half-life depends on initial concentration.

45. Identify the unit of the rate constant for a third-order reaction.

    $M^{-2}$ $s^{-1}$. Pattern: $M^{1-n}s^{-1}$ where n=3.

46. Identify the order of reaction if rate = k[A]^2.

    Second order with respect to A. Exponent of [A] is 2.

47. What effect does increasing temperature generally have on reaction rate?

    Increases the reaction rate. Higher temperature means faster molecular motion.

48. What is the role of a catalyst in a chemical reaction?

    Speeds up the reaction without being consumed. Lowers activation energy but remains unchanged.

49. What is the purpose of a rate law?

    To express how the rate depends on concentrations. Mathematical relationship between rate and concentration.

50. What is the effect of pressure on the rate of a gaseous reaction?

    Increasing pressure increases the rate. Higher pressure increases concentration of gases.

51. Identify the order of reaction if rate = k[A][B].

    Second order overall. Sum of exponents: 1 + 1 = 2.

52. What is the relationship between temperature and the rate constant?

    Rate constant increases with temperature. Exponential relationship from Arrhenius equation.

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