Chemical Reactions

The diagram shows apparatus used to investigate two different reactions that produce gases.

The reactants for each experiment are mixed and the mass of flask plus contents for each experiment is recorded every 30 seconds.

A graph of the mass against time is drawn.

In experiment 1, solid X is calcium carbonate.

In experiment 2, solid X is magnesium.

Which graph is correct?

Options

In a closed flask, gases Q and R reach a dynamic equilibrium.

$$\text{Q}(\text{g}) \rightleftharpoons 2\text{R}(\text{g}) \quad \Delta H\text{ is positive}$$

Which change will move the equilibrium to the right?

Options

A   adding a catalyst
B   decreasing the temperature
C   increasing the pressure
D   increasing the volume of the flask

Which row shows the typical conditions used for the conversion of sulfur dioxide to sulfur trioxide in the Contact process?

Options

The pH of dilute ethanoic acid is measured. The equation for the partial dissociation of ethanoic acid is shown.

$$\text{CH}_3\text{COOH}(\text{aq}) \rightleftharpoons \text{CH}_3\text{COO}^-(\text{aq}) + \text{H}^+(\text{aq})$$

Aqueous sodium ethanoate, $\text{CH}_3\text{COONa}$, is added to the dilute ethanoic acid and the pH is measured again.

What is the initial pH of the dilute ethanoic acid and how does it change after the addition of the aqueous sodium ethanoate?

Options

Which process is a chemical change?

Options

A   the distillation of aqueous ethanol
B   the evaporation of water from aqueous sodium chloride
C   the melting of wax
D   the rusting of iron

Aqueous sodium thiosulfate reacts with hydrochloric acid. The rate of the reaction increases if the concentration of both reactants is increased.

Nitrogen gas reacts with hydrogen gas. The rate of the reaction increases if the pressure in the reaction vessel is increased.

Which row correctly explains why the given change increases the rate of the reaction?

Options

Magnesium reacts with dilute sulfuric acid.

$$\text{Mg(s)} + \text{H}_2\text{SO}_4\text{(aq)} \rightarrow \text{MgSO}_4\text{(aq)} + \text{H}_2\text{(g)}$$

Two experiments are carried out at $25\,^\circ\text{C}$.

experiment 1: $24.0\text{ g}$ of powdered magnesium is reacted with $100\text{ cm}^3$ of $1.0\text{ mol / dm}^3$ sulfuric acid.

experiment 2: $24.0\text{ g}$ of powdered magnesium is reacted with $50\text{ cm}^3$ of $2.0\text{ mol / dm}^3$ sulfuric acid.

During each experiment, the volume of hydrogen produced is measured at regular time intervals.
The results are plotted on a graph.

Which graph is correct?

Options

Which row gives the catalyst for each of the two processes?

Options

The rate of reaction between calcium carbonate and dilute hydrochloric acid is measured in three separate experiments.

In experiment 1, the calcium carbonate is powdered, and an excess of hydrochloric acid is used.

In experiment 2, the calcium carbonate is in lumps, and an excess of hydrochloric acid is used.

In experiment 3, the calcium carbonate is in lumps, less hydrochloric acid is used, and the calcium carbonate is in excess.

The results of these experiments are shown.

Which statement is correct?

Options

A   Experiment 1 is shown by curve X.
B   Experiment 1 is shown by curve Y.
C   Experiment 2 is shown by curve Y.
D   Experiment 3 is shown by curve Z.

The equation shows the reversible reaction between nitrogen and hydrogen to form ammonia.

$$\text{N}_2 + 3\text{H}_2 \rightleftharpoons 2\text{NH}_3$$

The forward reaction is exothermic.

Which statement is correct when the temperature is increased?

Options

A   The activation energy increases.
B   The equilibrium shifts to form more ammonia.
C   The rate of the forward reaction decreases.
D   The rate at which ammonia decomposes increases.