Unit 8: Chemical Reactivity
Difficult MCQs
- What is the role of a catalyst in a chemical reaction?
- A) To increase the activation energy
- B) To decrease the activation energy
- C) To alter the equilibrium constant
- D) To change the concentration of reactants
- Answer: B) To decrease the activation energy
- The rate law for a reaction is given by rate = k[A][B]^2. What is the order of the reaction with respect to B?
- A) 1
- B) 2
- C) 3
- D) 0
- Answer: B) 2
- In which type of reaction does a single reactant produce multiple products?
- A) Combination reaction
- B) Decomposition reaction
- C) Single displacement reaction
- D) Double displacement reaction
- Answer: B) Decomposition reaction
- What is the half-life of a first-order reaction dependent on?
- A) Initial concentration of reactants
- B) Temperature
- C) The rate constant
- D) Both B and C
- Answer: D) Both B and C
- For which type of reaction is the equilibrium constant independent of temperature?
- A) Endothermic reactions
- B) Exothermic reactions
- C) Reactions with no change in enthalpy
- D) All reactions
- Answer: C) Reactions with no change in enthalpy
- What is the effect of increasing the pressure on a reaction at equilibrium involving gases?
- A) It always shifts the equilibrium to the right
- B) It always shifts the equilibrium to the left
- C) It shifts the equilibrium toward the side with fewer moles of gas
- D) It has no effect on the equilibrium
- Answer: C) It shifts the equilibrium toward the side with fewer moles of gas
- Which of the following statements is true about the rate constant of a reaction?
- A) It depends on the concentration of reactants
- B) It is constant at all temperatures
- C) It changes with temperature
- D) It is affected by the presence of a catalyst
- Answer: C) It changes with temperature
- What is the term for the energy required to break one mole of bonds in gaseous molecules?
- A) Bond dissociation energy
- B) Activation energy
- C) Enthalpy change
- D) Gibbs free energy
- Answer: A) Bond dissociation energy
- What is the effect of a catalyst on the equilibrium position of a reaction?
- A) It shifts the equilibrium position
- B) It changes the equilibrium constant
- C) It increases the rate at which equilibrium is reached
- D) It does not affect the equilibrium position
- Answer: C) It increases the rate at which equilibrium is reached
- In a zero-order reaction, what happens to the rate of the reaction if the concentration of the reactant is doubled?
- A) The rate remains the same
- B) The rate doubles
- C) The rate quadruples
- D) The rate is halved
- Answer: A) The rate remains the same