Chemistry 5070 · O Level · Reversible reactions and equilibrium

Reversible reactions and equilibrium — practice question

Nitrogen dioxide, $\text{NO}_2$, combines with itself to form dinitrogen tetroxide, $\text{N}_2\text{O}_4$, in an exothermic reaction. This reaction is studied at $140^\circ\text{C}$ inside a sealed container. A dynamic equilibrium mixture is then obtained. $2\text{NO}_2(g) \rightleftharpoons \text{N}_2\text{O}_4(g)$ $\text{NO}_2(g)$ is a dark brown gas. $\text{N}_2\text{O}_4(g)$ is a colourless gas.
(a)[1]

What does the symbol $\rightleftharpoons$ represent?

(b)[1]

What is meant by an exothermic reaction?

(c)[1]

Suggest why a sealed container has to be used to establish equilibrium.

(d)[2]

The pressure of the equilibrium mixture is lowered. The temperature stays at $140^\circ\text{C}$. Predict and explain how the colour of the equilibrium mixture will change.

(e)[2]

The temperature of the equilibrium mixture is raised. The pressure remains constant. Predict and explain what will happen to the colour of the equilibrium mixture.

(f(i))[2]

Describe an experiment that would let you tell apart separate solutions of a strong acid and a weak acid.

(f(ii))[1]

Nitrogen dioxide reacts with aqueous potassium hydroxide. State the formula of each of the two salts produced in this reaction.

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