SL Kinetics 2024 IB

In a reaction, the change in concentration of a product with time is shown by the dashed line X on the graph below.

Which of the lines, A to D, shows the effect of adding a catalyst to this reaction?

• A

• B

• C

• D

Consider the following reaction carried out with 0.10 g of magnesium ribbon and excess hydrochloric acid.

Mg(s) + 2HCl (aq) --> MgCl₂(aq) + H₂(g)

Which method should be used to follow the rate of this reaction?

• Measure the pH of the solution, using a pH meter.

• Measure the colour of the solution, using a colorimeter.

• Measure the volume of gas being formed, using a gas syringe.

• Measure the mass of the mixture, using a balance which weighs to two decimal places.

How does the addition of a catalyst to a reaction affect the shape of the Maxwell-Boltzmann distribution curve?

• There is no change.

• The peak moves to the left and is higher.

• The peak moves to the right and is lower.

• The total area under the curve increases.

Marble chips react with dilute hydrochloric acid.

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

An experiment was carried out to measure the initial rate of this reaction at 20 °C.

The experiment was repeated keeping the mass of marble chips and the volume and concentration of the hydrochloric acid constant.

Which set of changes will result in the fastest initial rate of reaction?

• A

• B

• C

• D

The diagram below shows the Maxwell-Boltzmann distribution for the molecular energies of a gaseous system at two temperatures, and the activation energy for both uncatalysed, E_a , and catalysed, E_a(cat), reactions.

 The main reason why an increase in temperature increases the rate of a chemical reaction is because

• the activation energy increases.

• the activation energy decreases.

• collisions occur with greater energy.

• collisions occur more frequently.

The diagram below shows the Maxwell-Boltzmann distribution for the molecular energies of a gaseous system at two temperatures, and the activation energy for both uncatalysed, E_a , and catalysed, E_a(cat), reactions.

 TConsider only the Maxwell-Boltzmann distribution at the higher temperature.

Which area of the graph shows the additional number of particles with energy greater than the activation energy, due to the presence of the catalyst?

• Area X

• Area W + X

• Area X + Z

•   Area W + X + Y + Z

This question is about the Maxwell-Boltzmann energy distribution.

The diagram for an increase in temperature from T₁ to T₂ is

• 
• 
• 
• 

The rate of the reaction between calcium carbonate and acid increases when

• the particle size of the calcium carbonate decreases.

• 1 mol dm^–3 nitric acid is used instead of 1 mol dm^–3 hydrochloric acid.

• 0.5 mol dm^–3 sulfuric acid is used instead of 1 mol dm^–3 hydrochloric acid.

• the pressure is increased.

Consider the following reaction:

Increasing the pressure increases the reaction rate because it

•  increases molecular energies.

•  shifts the position of equilibrium to the right.

•  increases the collision frequency.

• decreases the activation energy.

An energy level diagram for a reaction with an intermediate can be drawn as shown.

Which arrow indicates the enthalpy change for this reaction?

• A

• B

• C

• D