Chemistry Test: Rate of Chemical Reactions

Rate of Appearance/Disappearance & Factors Affecting Reaction Rates

Instructions:

1. This test contains 30 multiple-choice questions
2. Each question has four options
3. Select the correct option for each question
4. Press the 'Submit' button when you finish
5. After submission, correct answers will be shown

1. For the reaction: 2N₂O₅ → 4NO₂ + O₂, if the rate of disappearance of N₂O₅ is 2.4 × 10⁻⁴ M/s, what is the rate of appearance of O₂?

a. 1.2 × 10⁻⁴ M/s

b. 2.4 × 10⁻⁴ M/s

c. 4.8 × 10⁻⁴ M/s

d. 9.6 × 10⁻⁴ M/s

2. For the reaction: 2A + 3B → 4C, which expression correctly relates rates of disappearance and appearance?

a. -Δ[A]/Δt = -Δ[B]/Δt = Δ[C]/Δt

b. -½Δ[A]/Δt = -⅓Δ[B]/Δt = ¼Δ[C]/Δt

c. -Δ[A]/Δt = -Δ[B]/Δt = Δ[C]/Δt

d. -½Δ[A]/Δt = -⅓Δ[B]/Δt = Δ[C]/Δt

3. In the reaction: 2NO + O₂ → 2NO₂, if the rate of formation of NO₂ is 5.0 × 10⁻⁵ M/s, what is the rate of disappearance of NO?

a. 2.5 × 10⁻⁵ M/s

b. 5.0 × 10⁻⁵ M/s

c. 1.0 × 10⁻⁴ M/s

d. 2.5 × 10⁻⁴ M/s

4. The rate of disappearance of a reactant is always:

a. Positive

b. Negative

c. Zero

d. Equal to the rate of appearance of products

5. For the reaction: A → 2B, if the rate of disappearance of A is 0.04 M/s, what is the rate of appearance of B?

a. 0.02 M/s

b. 0.04 M/s

c. 0.08 M/s

d. 0.16 M/s

6. In the reaction: 2H₂O₂ → 2H₂O + O₂, if the rate of formation of O₂ is 3.2 × 10⁻³ M/s, what is the rate of disappearance of H₂O₂?

a. 3.2 × 10⁻³ M/s

b. 6.4 × 10⁻³ M/s

c. 1.6 × 10⁻³ M/s

d. 9.6 × 10⁻³ M/s

7. Which of the following expressions correctly defines the rate of a reaction: aA + bB → cC + dD?

a. Rate = -1/a Δ[A]/Δt = -1/b Δ[B]/Δt = 1/c Δ[C]/Δt = 1/d Δ[D]/Δt

b. Rate = Δ[A]/Δt = Δ[B]/Δt = Δ[C]/Δt = Δ[D]/Δt

c. Rate = -Δ[A]/Δt = -Δ[B]/Δt = Δ[C]/Δt = Δ[D]/Δt

d. Rate = 1/a Δ[A]/Δt = 1/b Δ[B]/Δt = 1/c Δ[C]/Δt = 1/d Δ[D]/Δt

8. For the reaction: 2NO₂ → 2NO + O₂, if the rate of decomposition of NO₂ is 4.8 × 10⁻⁶ M/s, what is the rate of formation of O₂?

a. 2.4 × 10⁻⁶ M/s

b. 4.8 × 10⁻⁶ M/s

c. 9.6 × 10⁻⁶ M/s

d. 1.92 × 10⁻⁵ M/s

9. In the reaction: 4NH₃ + 5O₂ → 4NO + 6H₂O, if the rate of consumption of O₂ is 0.02 M/s, what is the rate of formation of NO?

a. 0.016 M/s

b. 0.02 M/s

c. 0.025 M/s

d. 0.03 M/s

10. The rate of appearance of a product is always:

a. Positive

b. Negative

c. Zero

d. Equal to the rate of disappearance of reactants

11. Which factor does NOT generally affect the rate of a chemical reaction?

a. Concentration of reactants

b. Temperature

c. Presence of a catalyst

d. The enthalpy change of the reaction (ΔH)

12. Increasing the temperature of a reaction generally increases the reaction rate because:

a. It increases the activation energy

b. It increases the number of collisions with proper orientation

c. It increases average kinetic energy of molecules

d. It decreases the activation energy

13. A catalyst increases the rate of a reaction by:

a. Increasing temperature of reaction

b. Increasing concentration of reactants

c. Providing an alternative pathway with lower activation energy

d. Increasing surface area of reactants

14. For a reaction with a large activation energy, the reaction rate will be:

a. Fast

b. Slow

c. Unaffected by temperature

d. Independent of concentration

15. Increasing the surface area of a solid reactant will increase the reaction rate because:

a. It increases the concentration

b. It increases the temperature

c. It provides more sites for collisions

d. It decreases activation energy

16. According to collision theory, for a reaction to occur, molecules must:

a. Have sufficient kinetic energy

b. Have proper orientation

c. Collide with each other

d. All of the above

17. The Arrhenius equation describes the relationship between reaction rate and:

a. Concentration

b. Temperature

c. Surface area

d. Pressure

18. Which of the following would NOT increase the rate of a reaction?

a. Increasing the temperature

b. Adding a catalyst

c. Decreasing the concentration of reactants

d. Increasing the surface area of a solid reactant

19. The minimum energy required for a reaction to occur is called:

a. Kinetic energy

b. Potential energy

c. Activation energy

d. Thermal energy

20. For gaseous reactants, increasing the pressure will increase the reaction rate because:

a. It increases the temperature

b. It increases the concentration

c. It decreases the activation energy

d. It provides a catalyst

21. In the reaction: 2HI → H₂ + I₂, the rate of disappearance of HI is 1.8 × 10⁻³ M/s. What is the rate of appearance of I₂?

a. 1.8 × 10⁻³ M/s

b. 9.0 × 10⁻⁴ M/s

c. 3.6 × 10⁻³ M/s

d. 0.9 × 10⁻³ M/s

22. Which of the following would increase the rate of the reaction: Zn(s) + 2HCl(aq) → ZnCl₂(aq) + H₂(g)?

a. Using zinc powder instead of zinc chunks

b. Decreasing the concentration of HCl

c. Lowering the temperature

d. Using a smaller container

23. For the decomposition of hydrogen peroxide: 2H₂O₂ → 2H₂O + O₂, a catalyst is often used. What is the effect of the catalyst?

a. It increases the activation energy

b. It decreases the activation energy

c. It increases the ΔH of the reaction

d. It decreases the ΔH of the reaction

24. The rate of a reaction quadruples when the temperature is increased from 300K to 320K. What is the activation energy of the reaction? (Assume Arrhenius behavior)

a. 53.6 kJ/mol

b. 107.2 kJ/mol

c. 26.8 kJ/mol

d. 214.4 kJ/mol

25. In the reaction: 2NO + Cl₂ → 2NOCl, if the concentration of NO is doubled and the concentration of Cl₂ is halved, the rate of reaction will:

a. Remain the same

b. Double

c. Quadruple

d. Be halved

26. For a zero-order reaction, the rate is:

a. Proportional to the concentration of the reactant

b. Proportional to the square of the concentration of the reactant

c. Independent of the concentration of the reactant

d. Inversely proportional to concentration

27. For a first-order reaction, the half-life is:

a. Proportional to initial concentration

b. Independent of initial concentration

c. Proportional to the square of initial concentration

d. Inversely proportional to initial concentration

28. Which statement about catalysts is correct?

a. They are consumed in reaction

b. They alter equilibrium position

c. They increase reaction rate without being consumed

d. They increase enthalpy change

29. The rate constant has units of s⁻¹. The order is:

a. Zero order

b. First order

c. Second order

d. Third order

30. Which graph represents a first-order reaction?

a. [A] vs t straight line

b. ln[A] vs t straight line

c. 1/[A] vs t straight line

d. t vs [A]² straight line