Reaction Kinetics (CIE AS Chemistry)

The distribution of molecular energies in a sample of a gas at a given temperature is shown by the Boltzmann distribution graph below. 

If the temperature is increased, what will happen to the position of point X?

The diagram shows a reaction pathway for an endothermic reaction.

Which arrow represents the activation energy for the forward reaction?

The dotted-line curve on each graph below represents the corresponding distribution for a gas at 300 K. 

Which solid-line curve most accurately represents the distribution of molecular energies in the same gas at 500 K?

The energies of the reactants, the products and the transition state of a reaction are shown in the reaction pathway diagram below.

Which expression correctly represents how to calculate the activation energy of the forward reaction?

The diagram below represents, for a given temperature, the Boltzmann distribution of the kinetic energy of the molecules in a mixture of two gases that react slowly together without a catalyst.

The activation energy for the reaction, E_a, is marked for the uncatalysed reaction.

What would the position of E_a be if the reaction took place with an effective catalyst?

Four possible reactions (A, B, C and D) of the equation below are measured at the same temperature.

X (g) + Y (g) → Z (g)

Which reaction pathway diagram shows the reaction that would proceed most rapidly and with good yield?

The diagram shows a Boltzmann distribution of molecular energies for a gaseous mixture. The distribution has a peak, labelled Q on the diagram.

What happens when an effective catalyst is added to the mixture?

A student performs two reactions and measures the rate of product formation. 

Reaction 1: 1.5 g of solid calcium carbonate is added to 100 cm³ of 0.5 M hydrochloric acid.

Reaction 2: 100 cm³ of distilled water is then added to 100 cm³ of 0.5 M hydrochloric acid then 1.5 g of solid calcium carbonate is added.

The rate of reaction 1 was faster than the rate of reaction 2. 

Which of the following 3 hypotheses correctly describes the difference in the rate? 

The Boltzmann distribution shows the number of molecules that have particular kinetic energy at a constant temperature.

If the temperature is decreased by 10 °C, what happens to the size of the areas labelled H, J and K?

Photochromic glass is used for some glasses to enable them to work as sunglasses. The glass darkens when exposed to bright light and returns to transparent again when the light is less bright. The darkness of the colour of the glass is related to the concentration of silver atoms. 

The following reactions are involved.

Which statement about these reactions is correct?

When 1 cm³ of 0.1 mol dm^–3 HCl is added to 10 cm³ of 0.02 mol dm^–3 Na₂S₂O₃ pale yellow precipitate forms slowly.

When the experiment is repeated with 1 cm³ of 0.1 mol dm^–3 HCl and 10 cm³ of 0.05 mol dm^–3 Na₂S₂O₃ the precipitate forms more quickly.

Why is this?

A reaction is zero order with respect to a reactant A.

Which concentration–time graph for reactant A is the correct shape?

A quantity of solid Y was placed in a previously evacuated vessel, and the apparatus was then held at a series of different temperatures. At each temperature, the mass of Y in the vapour state was calculated from pressure measurements. The results are shown below.

What can be deduced from the diagram?

On the graph, curve 1 was produced from measuring the decomposition of 100 cm³ of 1.0 mol dm^–3 hydrogen peroxide in the presence of a manganese (IV) oxide catalyst.

Which alteration to the original experimental conditions would produce curve 2?

The following exothermic reaction occurs during a fireworks display.

16Al + 3Ba(NO₃)₂ + 36H₂O → 3Ba(OH)₂ + 16Al (OH)₃ + 6NH₃

The production of sparkler fireworks requires a mixture of barium nitrate powder and aluminium powder to be mixed with water before being glued on to wires. The wire coating must be dry before lighting the fireworks.

Which conditions would be best to reduce the rate of this reaction during the drying process, and would also keep the aluminium and barium nitrate unchanged?

The stoichiometry of a catalysed reaction is shown by the equation below.

R (g) + S (g)     T (g) + U (g)

Two experiments were carried out in which the amount of product T was measured against time. The results are shown in the diagram below.

Which changes in the conditions from experiment 1 to experiment 2 might explain the results shown?

Boltzmann distributions are shown in the diagrams.

In diagram 1, one line, P or Q, corresponds to the activation energy in the presence of a catalyst and the other line corresponds to the activation energy of the same reaction in the absence of a catalyst.

In diagram 2, one curve, X or Y, corresponds to a temperature higher than that of the other curve. 

Which combination gives the correct curve and line?