Maxwell-Boltzmann distribution

Nitrogen monoxide, NO, reacts with oxygen to form nitrogen dioxide, NO₂.

The rate of reaction increases in the presence of a heterogeneous platinum catalyst.

Explain why platinum is an example of a heterogeneous catalyst for Reaction 18.1.

Explain how the platinum catalyst increases the rate of reaction.

Include a labelled sketch of the Boltzmann distribution on the grid.

In industry, catalysts have great economic importance and benefits for increased sustainability.

Explain how the use of catalysts is beneficial to the environment.

The following data was obtained in a series of experiments on the rate of the reaction for Reaction 18.1 at a constant temperature.

Determine the orders with respect to NO and O₂. Explain your reasoning.

Determine the rate equation and calculate the rate constant, k, including units.

Complete the table by adding the missing value of ln k.

Which row in the table explains how a catalyst affects the activation energy (E_a) and the proportion of molecules with energy > E_a?

Your answer

A catalytic converter in a car removes nitrogen monoxide, NO, and carbon monoxide, CO, from the exhaust gases.

One reaction that happens in a catalytic converter is shown below.

Explain how increasing the temperature increases the rate of Reaction 16.1.

Include a labelled sketch, using Boltzmann distributions, on the grid below.

Label the axes.

Carbon monoxide also reacts with nitrogen dioxide as shown in Reaction 16.2.

The rate equation for Reaction 16.2 is shown below:

rate = k [NO₂(g)]²

Suggest a possible two-step mechanism for Reaction 16.2. The first step is much slower than the second step.

Two students plan to investigate Equilibrium 4.1, shown below.

The students are supplied with the equilibrium mixture in Equilibrium 4.1 at room temperature.

• One student heats 20 cm³ of the mixture to 50 °C.

• The other student heats 20 cm³ of the mixture to 90 °C.

The students use colorimetry to observe how the colour of the equilibrium mixture changes over time.

• The colorimeter is set up so that the greater the absorbance, the greater the

The students plot the graph below from the results of the experiment.

Use the graph and relevant chemical theory to answer the following. Include all reasoning:

• Explain the different initial rates at 50 °C and 90 °C.

• Predict the sign of ∆ H for the forward reaction in Equilibrium 4.1.

The students investigate how addition of aqueous silver nitrate, AgNO₃(aq), affects the equilibrium position in Equilibrium 4.1.

The graph shows the changes in the equilibrium concentrations of CoCl₄^2–, Cl^– and [Co(H₂O)₆]²⁺ after addition of the AgNO₃(aq).

The AgNO₃(aq) is added at time = t₁.

Explain why the Cl^– concentration drops sharply at time = t₁.

Which statement(s) explain(s) why reaction rates increase as temperature increases?

1 The activation energy is less.

2 Collisions between molecules are more frequent.

3 A greater proportion of molecules have energy greater than the activation energy.

A 1, 2 and 3

B Only 1 and 2

C Only 2 and 3

D Only 1

Your answer