Chemistry 5070 · O Level · The mole and the Avogadro constant

The mole and the Avogadro constant — practice question

Aqueous ammonium nitrite, $\text{NH}_4\text{NO}_2(aq)$, breaks down on heating, as shown: $\text{NH}_4\text{NO}_2(aq) \rightarrow \text{N}_2(g) + 2\text{H}_2\text{O}(l)$.
(a)[2]

A $25.0\,\text{cm}^3$ portion of $0.150\,\text{mol dm}^{-3}$ $\text{NH}_4\text{NO}_2(aq)$ is heated. Calculate the greatest volume, in $\text{dm}^3$, of nitrogen produced at room temperature and pressure.

(b)[3]

The concentration of $\text{NH}_4\text{NO}_2(aq)$ is reduced. The reaction temperature stays constant. State and explain how the rate of reaction is affected.

(c)[3]

$\text{NH}_4\text{NO}_2$ contains the ammonium ion, $\text{NH}_4^+$, and the nitrite ion. A mixture of aqueous calcium hydroxide and $\text{NH}_4\text{NO}_2(s)$ is warmed. Calcium nitrite, water and a gas are produced. The gas turns damp red litmus paper blue. Write the equation for this reaction.

(d(i))[1]

$\text{NH}_4\text{NO}_2(aq)$ is added to a sample of aqueous potassium iodide. A brown solution forms. Name the brown solution.

(d(ii))[1]

Name the type of reaction responsible for the formation of this brown solution.

Worked solution & mark scheme

This 10-mark question has a full step-by-step worked solution and mark scheme. One marking point: moles of NH4NO2 were 0.00375

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