Topic 6: Chemical Kinetics (SL & HL)

The diagram below represents a Maxwell-Boltzmann energy distribution of a gas at a temperature, T. How will the curve change if the temperature is decreased, while other conditions remain constant?

• The maximum is lower than and to the left of the arrow.

• The maximum is higher than and to the right of the arrow.

• The maximum is lower than and to the right of the arrow.

• The maximum is higher than and to the left of the arrow.

Answer explanation

Which properties may be monitored to determine the rate of reaction?

Zn(s) + CuSO₄(aq) → ZnSO₄(aq) + Cu(s)

1: The change in total volume of solution

2: The change in color of the solution

3: The change in temperature of the solution

• 1, 2 and 3

• 1 and 2 only

• 2 only

• 2 and 3 only

Answer explanation

The dotted line represents the volume of hydrogen gas evolved over time when excess magnesium ribbon is added to hydrochloric acid. Which line represents the production of hydrogen gas when excess magnesium ribbon is added to the same volume of hydrochloric acid with half the concentration?

• A

• B

• C

• D

Answer explanation

The dotted line represents the volume of oxygen gas (O₂) evolved over time when a sample of hydrogen peroxide (H₂O₂) decomposes. Which line represents the production of oxygen gas when a catalyst is added to the same volume of hydrogen peroxide decomposing under the same conditions?

• A

• B

• C

• D

Answer explanation

Which represents the activation energy for the reverse reaction?

• A

• B

• C

• D

Answer explanation

Several reactions of calcium carbonate chips with dilute hydrochloric acid are carried out at room temperature.

CaCO₃(s) + 2HCl(aq) → CaCl₂(aq) + H₂O(l) + CO₂(g)

Which of the following has the greatest initial rate of reaction?

• 3 only

• 1 only

• 1 and 2

• 2 only

Answer explanation

Several reactions of excess solid sodium carbonate with dilute hydrochloric acid are carried out at room temperature.

Na₂CO₃(s) + 2HCl(aq) → 2NaCl(aq) + H₂O(l) + CO₂(g)

Which statement is correct?

• Reactions 1 and 2 will produce the same total mass of CO₂.

• The initial rate for all three reactions will be the same.

• Reaction 1 will have the greatest initial rate of reaction.

• Reaction 2 will produce twice the total mass of CO₂ as reaction 3.

Answer explanation

Which changes would increase the rate of reaction when zinc reacts with excess copper sulfate solution, assuming that all other conditions remain the same?

Zn(s) + CuSO₄(aq) → ZnSO₄(aq) + Cu(s)

1: Increasing the temperature

2: Using larger pieces of zinc (of the same mass)

3: Diluting the copper sulfate solution by adding water

• 2 only

• 1 and 2 only

• 1 only

• 1, 2 and 3

Answer explanation

Excess magnesium ribbon was added to hydrochloric acid, and the mass of the reaction vessel was monitored over time to give line X. If the reaction was repeated, which change could give line Y, assuming all other conditions remained the same?

• Cutting the magnesium ribbon into smaller pieces

• Increasing the temperature

• Increasing the mass of magnesium ribbon

• Using more concentrated hydrochloric acid

Answer explanation

Which of the following is/are true with respect to the action of a catalyst on increasing the rate of a chemical reaction?

1: The activation energy decreases

2: A greater proportion of particles have enough energy needed to react

3: There are a greater number of particle collisions

• 1, 2 and 3

• 1 and 2 only

• 2 only

• 1 only

Answer explanation