IB Chemistry Quiz: Understand Rate Of Chemical Change

What this quiz covers

This quiz focuses on Understand Rate Of Chemical Change, giving you a quick way to practice the rules, question types, and explanations that matter most for IB Chemistry.

How to use this quiz

Try each quiz question before looking at the correct answer. Use the explanations to review missed ideas, then come back to similar questions until the pattern feels familiar.

Question 1

1. (-150 \text{ kJ mol}^{-1}\
2. (-100 \text{ kJ mol}^{-1}\
3. (+100 \text{ kJ mol}^{-1}\ (correct answer)
4. (+200 \text{ kJ mol}^{-1}\

Question 2

1. a single 1.0 g pellet to ensure it is not washed away by the effervescence.
2. a fine powder to maximize the number of active sites available for reaction. (correct answer)
3. dissolved in the aqueous solution to create a homogeneous catalytic system.
4. a 1.0 g pellet heated to a high temperature before being added to the solution.

Question 3

1. It increases the rates of both the forward and reverse reactions. (correct answer)
2. It shifts the equilibrium position to the right to favor product formation.
3. It increases the percentage yield of ammonia at equilibrium.
4. It decreases the activation energy for the forward reaction but not the reverse reaction.

Question 4

1. I and II only
2. I and III only
3. II and III only
4. I, II and III (correct answer)

Question 5

1. The total time taken for the reaction to complete.
2. The total volume of gas produced by the end of the reaction.
3. The method used for measuring the volume of gas.
4. The initial temperature of the acid solution. (correct answer)

Question 6

1. The frequency of effective collisions between reactant particles A and B decreases. (correct answer)
2. The temperature of the system decreases as the reaction is endothermic.
3. The activation energy of the reaction increases as the concentration of product C increases.
4. The catalyst for the reaction is being consumed, making it less effective over time.

Question 7

1. The total surface area of the reactant is decreased. (correct answer)
2. The concentration of the solid reactant is lower in the lumps.
3. The activation energy is higher for the lumps than for the powder.
4. The lumps are less pure than the powdered form of the reactant.

Question 8

1. The rate of the forward reaction increases because the activation energy is decreased.
2. The rate of the forward reaction increases because the frequency of molecular collisions increases. (correct answer)
3. The rate of the forward reaction decreases because the average distance between molecules increases.
4. The rate of the forward reaction is unchanged because the kinetic energy of the molecules is constant.

Question 9

1. Rate is faster; total volume of H₂ is greater.
2. Rate is faster; total volume of H₂ is the same. (correct answer)
3. Rate is the same; total volume of H₂ is greater.
4. Rate is the same; total volume of H₂ is the same.

Question 10

1. Increasing the concentration of $\text{H}_2\text{C}_2\text{O}_4$(aq).
2. Increasing the pressure above the reaction mixture. (correct answer)
3. Warming the reaction mixture from 20 °C to 30 °C.
4. Adding a small amount of $\text{MnSO}_4$(aq), a known autocatalyst for this reaction.

Question 11

1. The rate is constant throughout the reaction because the acid is in excess.
2. The rate is fastest at the beginning and gradually decreases until the reaction stops. (correct answer)
3. The rate increases over time as the reaction is exothermic, which heats the mixture.
4. The rate is zero at the start and increases to a maximum before decreasing to zero.

Question 12

1. The mechanism is consistent but requires modification of the equilibrium constant expression for the pre-equilibrium step
2. The mechanism is inconsistent because the predicted rate law would show first-order dependence on [NO]
3. The mechanism is inconsistent because the fast pre-equilibrium assumption cannot account for second-order NO dependence
4. The mechanism is consistent with the experimental data and predicts a rate law of rate = k₂K₁[NO]²[Cl₂] (correct answer)

Question 13

1. 0.15 mol L⁻¹
2. 0.20 mol L⁻¹ (correct answer)
3. 0.24 mol L⁻¹
4. 0.30 mol L⁻¹

Question 14

1. The ratio will be greater than 5 because the faster reaction benefits more from temperature increase
2. The ratio will be less than 5 because temperature increases favor the slower reaction more significantly
3. The ratio will remain exactly 5 because both reactions have the same activation energy (correct answer)
4. The ratio cannot be determined without knowing the specific activation energy values

Question 15

1. $2.8 \times 10^{-3}$ mol L⁻¹ s⁻¹ (correct answer)
2. $6.3 \times 10^{-3}$ mol L⁻¹ s⁻¹
3. $1.4 \times 10^{-3}$ mol L⁻¹ s⁻¹
4. $8.4 \times 10^{-3}$ mol L⁻¹ s⁻¹

Question 16

1. rate = k₂K_{eq}[A][B][D] (correct answer)
2. rate = k₂[A][B][D]/K_{eq}
3. rate = k₂K_{eq}[C][D]
4. rate = k₂[C][D]

Question 17

1. The curve flattens and shifts to the right, and $E_a$ decreases.
2. The curve is unchanged, but $E_a$ decreases. (correct answer)
3. The curve's peak increases in height and shifts left, and $E_a$ is unchanged.
4. The curve is unchanged, but $E_a$ increases.

Question 18

1. It increases the average kinetic energy of reactant particles, making collisions more effective.
2. It is consumed during the reaction while providing an alternative, faster reaction pathway.
3. It provides an alternative reaction mechanism which has a lower activation energy. (correct answer)
4. It increases the magnitude of the enthalpy change ($\Delta H$) of the reaction, causing it to proceed faster.

Question 19

1. Decreasing the concentration of the aqueous reactant and grinding the solid into a powder.
2. Increasing the temperature and using a single large piece of the solid reactant.
3. Increasing the temperature and grinding the solid reactant into a powder. (correct answer)
4. Decreasing the temperature and increasing the concentration of the aqueous reactant.

Question 20

1. It decreases the concentration of reactants by forming a stable compound with them.
2. It provides an alternative reaction pathway with a higher activation energy. (correct answer)
3. It lowers the temperature of the system by absorbing energy from the surroundings.
4. It reverses the enthalpy change of the reaction, making it less favorable.