Unit 8: Chemical Reactivity

  1. Which of the following best describes the effect of a catalyst on the energy profile of a reaction?
    • A) It increases the activation energy.
    • B) It decreases the activation energy.
    • C) It changes the overall energy change of the reaction.
    • D) It does not affect the energy profile of the reaction.
    • Answer: B) It decreases the activation energy.
  2. In a reaction that follows the rate law rate = k[A][B], if the concentration of A is doubled and the concentration of B is halved, what happens to the rate of the reaction?
    • A) The rate remains unchanged
    • B) The rate is doubled
    • C) The rate is halved
    • D) The rate is quartered
    • Answer: B) The rate is doubled
  3. Which of the following represents a true statement about equilibrium in a chemical reaction?
    • A) The concentrations of reactants and products are always equal.
    • B) The reaction proceeds only in the forward direction.
    • C) The rates of the forward and reverse reactions are equal.
    • D) The equilibrium constant changes with the concentration of reactants and products.
    • Answer: C) The rates of the forward and reverse reactions are equal.
  4. In the context of reaction kinetics, what does a negative reaction order indicate?
    • A) The reaction rate decreases with increasing reactant concentration.
    • B) The reaction rate increases with increasing reactant concentration.
    • C) The reaction rate remains constant regardless of reactant concentration.
    • D) The reaction does not proceed.
    • Answer: A) The reaction rate decreases with increasing reactant concentration.
  5. Which of the following is true for a reaction that is first-order with respect to each reactant?
    • A) The rate of reaction is proportional to the product of the concentrations of reactants.
    • B) The rate of reaction is proportional to the square of the concentrations of reactants.
    • C) The rate of reaction is proportional to the sum of the concentrations of reactants.
    • D) The rate of reaction is independent of the concentrations of reactants.
    • Answer: A) The rate of reaction is proportional to the product of the concentrations of reactants.
  6. What is the impact of increasing the concentration of a reactant on the rate of reaction for a reaction with a rate law of rate = k[A]^2?
    • A) The rate of reaction increases linearly.
    • B) The rate of reaction increases quadratically.
    • C) The rate of reaction decreases.
    • D) The rate of reaction remains unchanged.
    • Answer: B) The rate of reaction increases quadratically.
  7. Which of the following factors affects the rate of a reaction but does not change the equilibrium constant?
    • A) Temperature
    • B) Pressure
    • C) Catalyst
    • D) Concentration of reactants
    • Answer: C) Catalyst
  8. For a reaction that has a rate law rate = k[A][B]^2, what is the effect of doubling the concentration of A while keeping B constant?
    • A) The rate of reaction is halved.
    • B) The rate of reaction is doubled.
    • C) The rate of reaction is quadrupled.
    • D) The rate of reaction remains unchanged.
    • Answer: B) The rate of reaction is doubled.
  9. What is the effect of increasing the temperature on the rate constant for a reaction?
    • A) The rate constant decreases.
    • B) The rate constant remains constant.
    • C) The rate constant increases.
    • D) The rate constant becomes zero.
    • Answer: C) The rate constant increases.
  10. In a reaction that is second-order with respect to a reactant, what is the effect of tripling the concentration of that reactant?
    • A) The rate of reaction increases by a factor of 3.
    • B) The rate of reaction increases by a factor of 6.
    • C) The rate of reaction increases by a factor of 9.
    • D) The rate of reaction increases by a factor of 18.
    • Answer: C) The rate of reaction increases by a factor of 9.

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