Unit 8: Chemical Reactivity

  1. What happens to the reaction rate when the temperature is increased for an endothermic reaction?
    • A) The reaction rate decreases
    • B) The reaction rate remains constant
    • C) The reaction rate increases
    • D) The reaction rate becomes zero
    • Answer: C) The reaction rate increases
  2. In the reaction A + B → C, if the rate of reaction is increased by increasing the concentration of A, what does this imply about the reaction order with respect to A?
    • A) The reaction order is zero.
    • B) The reaction order is first.
    • C) The reaction order is second.
    • D) The reaction order is third.
    • Answer: B) The reaction order is first.
  3. Which of the following best describes a reaction that proceeds via a multi-step mechanism?
    • A) It has a single transition state
    • B) It has one rate-determining step
    • C) It has no intermediate steps
    • D) It occurs in a single step
    • Answer: B) It has one rate-determining step
  4. What is the effect of increasing the concentration of a reactant in a reaction with a rate law of rate = k[A][B]?
    • A) The rate increases proportionally
    • B) The rate decreases
    • C) The rate remains the same
    • D) The rate becomes zero
    • Answer: A) The rate increases proportionally
  5. The equilibrium constant K for a reaction is 10^3. What does this indicate about the reaction at equilibrium?
    • A) The reaction favors the reactants
    • B) The reaction favors the products
    • C) The reaction is at equilibrium with equal amounts of reactants and products
    • D) The reaction does not proceed
    • Answer: B) The reaction favors the products
  6. Which of the following is true about a first-order reaction?
    • A) The rate of reaction is proportional to the concentration of reactants.
    • B) The rate of reaction is proportional to the square of the concentration of reactants.
    • C) The rate of reaction is constant regardless of the concentration of reactants.
    • D) The rate of reaction depends on the concentration of products.
    • Answer: A) The rate of reaction is proportional to the concentration of reactants.
  7. What is the rate constant of a reaction that has a rate law rate = k[A]^2[B], if the reaction is second-order with respect to A and first-order with respect to B?
    • A) First-order
    • B) Second-order
    • C) Third-order
    • D) Zero-order
    • Answer: C) Third-order
  8. Which of the following statements about reaction mechanisms is false?
    • A) A mechanism is a step-by-step description of how a reaction occurs.
    • B) The sum of the elementary steps in a mechanism must equal the overall balanced equation.
    • C) The rate-determining step is the fastest step in a reaction mechanism.
    • D) Intermediates are formed and consumed within the mechanism.
    • Answer: C) The rate-determining step is the fastest step in a reaction mechanism.
  9. In a reaction where the equilibrium constant decreases with increasing temperature, what can be inferred about the reaction?
    • A) The reaction is endothermic
    • B) The reaction is exothermic
    • C) The reaction is at equilibrium
    • D) The reaction is non-spontaneous
    • Answer: B) The reaction is exothermic
  10. What is the effect of increasing the pressure on a reaction at equilibrium that involves a decrease in the number of gas molecules?
    • A) The equilibrium shifts to the left
    • B) The equilibrium shifts to the right
    • C) The equilibrium constant changes
    • D) The reaction rate increases
    • Answer: B) The equilibrium shifts to the right

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