Reaction Kinetics

A Boltzmann distribution for a sample of a reacting gas at a constant temperature is shown. The activation energy, $E_{\text{a}}$, for the reaction is marked.

Point $\times$ shows the number of particles whose energy is equal to the activation energy.

The temperature of the sample of gas is decreased. The shape of the distribution curve changes.

Which point could show the number of particles whose energy is the same as the activation energy at the new temperature?

Options

A   A
B   B
C   C
D   D

An aqueous solution of hydrogen peroxide is placed in a flask and decomposes, as shown.

$$2\text{H}_2\text{O}_2(\text{aq}) \rightarrow 2\text{H}_2\text{O}(\text{l}) + \text{O}_2(\text{g})$$

The total volume of oxygen gas evolved is $180\text{ cm}^3$ after 90 seconds, measured under room conditions.

The rate of the reaction is calculated using the equation shown.

$$\text{rate} = \frac{\text{change in moles of } \text{H}_2\text{O}_2}{\text{time}}$$

What is the average rate of the reaction, measured in $\text{mol min}^{-1}$, over the duration of the experiment?

Options

A   $8.33 \times 10^{-5}$
B   $1.67 \times 10^{-4}$
C   0.0050
D   0.010

The rate of the reaction between a reactive metal and an excess of a dilute acid is investigated.

The total volume of hydrogen gas produced is recorded every 30 seconds for 3 minutes.

The average rate of reaction during the first 30 seconds is P.

The average rate of reaction during the last 30 seconds is Q.

What is the value of P – Q?

Options

A   $1.21 \text{ cm}^3 \text{ s}^{-1}$
B   $1.93 \text{ cm}^3 \text{ s}^{-1}$
C   $2.13 \text{ cm}^3 \text{ s}^{-1}$
D   $3.43 \text{ cm}^3 \text{ s}^{-1}$

In the diagram, curve X was obtained by measuring the volume of oxygen produced during the decomposition of $100 \text{ cm}^3$ of $1.0 \text{ mol dm}^{-3}$ hydrogen peroxide. A catalyst of manganese(IV) oxide was used.

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

Options

A   adding more manganese(IV) oxide
B   adding some $0.1 \text{ mol dm}^{-3}$ hydrogen peroxide
C   adding water
D   raising the temperature

A possible mechanism for the exothermic hydrolysis of 2-chloro-2-methylpropane is shown.

Which diagram represents the reaction pathway diagram for this mechanism?

Options

A   Diagram A
B   Diagram B
C   Diagram C
D   Diagram D

The diagram shows a Boltzmann distribution of molecular energies for a gaseous reaction at two different temperatures and two different activation energies.

Which combination of temperature and activation energy will give the highest reaction rate?

Options

A   $T_1$ and $E_{\text{A}(1)}$
B   $T_1$ and $E_{\text{A}(2)}$
C   $T_2$ and $E_{\text{A}(2)}$
D   $T_2$ and $E_{\text{A}(1)}$

Aqueous hydrogen peroxide, $\text{H}_2\text{O}_2$, decomposes into water and oxygen in the presence of a suitable catalyst.

$50\text{ cm}^3$ of a $0.50\text{ mol dm}^{-3}$ solution of hydrogen peroxide produced $120\text{ cm}^3$ of oxygen in 2.0 minutes.

The volume of gas was measured at room conditions.

What is the average rate of decomposition of hydrogen peroxide during this 2.0 minute period?

Options

A   $0.000083\text{ mol dm}^{-3}\text{ s}^{-1}$
B   $0.00083\text{ mol dm}^{-3}\text{ s}^{-1}$
C   $0.0017\text{ mol dm}^{-3}\text{ s}^{-1}$
D   $0.10\text{ mol dm}^{-3}\text{ s}^{-1}$

Diagram 1 shows the reaction pathway for a reaction.

Diagram 2 shows a graph of concentration of reactant against time for the same reaction.

Which diagrams, drawn to the same scale, show the effect of increased temperature on this reaction?

Options

The gaseous compound Z decomposes on heating.

In the diagram, Boltzmann distributions for Z at two different temperatures, P and Q, are shown. The lines X and Y indicate activation energies for the decomposition of Z with and without a catalyst.

Which curve and which line describe the decomposition of Z at a higher temperature and with a catalyst present?

Options

The distribution of molecular energies in an ideal gas can be represented in a Boltzmann distribution.

Which change in conditions leads to a larger value for the number of molecules that have the most probable energy?

Options

A   keeping the temperature constant but decreasing the pressure
B   keeping the pressure constant but decreasing the temperature
C   keeping the temperature constant but increasing the pressure
D   keeping the pressure constant but increasing the temperature