Chemistry 9701 · AS & A Level · Group 17

Group 17 — practice question

Phosphorus and chlorine are both elements in Period 3 of the Periodic Table.
(a(i))[2]

Complete Table 1.1 by giving the oxidation number of phosphorus and the oxidation number of chlorine in $\text{PCl}_3$ and $\text{PCl}_5$.

(a(ii))[2]

In a closed system, $\text{PCl}_3$ and $\text{PCl}_5$ form an equilibrium mixture as shown in reaction 1: $\text{PCl}_3(l) + \text{Cl}_2(g) \rightleftharpoons \text{PCl}_5(s)$, $\Delta H = -124\,\text{kJ mol}^{-1}$. Deduce two conditions that promote the formation of $\text{PCl}_5$ in reaction 1.

(a(iii))[2]

The third phosphorus-chlorine compound, $\textbf{W}$, has a relative molecular mass, $M_r$, lying between those of $\text{PCl}_3$ and $\text{PCl}_5$. The compound is $69.6\%$ chlorine by mass. Determine the molecular formula of $\textbf{W}$.

(a(iv))[2]

$\textbf{W}$ is a liquid at room temperature and pressure. It reacts vigorously with water to produce an acidic solution. Suggest the structure and bonding in $\textbf{W}$. Explain your answer.

(b(i))[1]

Fig. 1.1 shows a reaction scheme involving $\text{P}_4$ and $\text{Cl}_2$. Suggest what is observed in reaction 2.

(b(ii))[1]

Predict the shape of a molecule of $\text{PCl}_5$.

(b(iii))[1]

Write an equation for the formation of $\textbf{A}$ in reaction 3.

(b(iv))[1]

Name $\textbf{B}$, which is formed in both reactions 4 and 5.

(b(v))[1]

Draw the structure of $\textbf{C}$, used in reaction 6.

(c(i))[1]

$1,2$-dichloroethane, $\text{ClCH}_2\text{CH}_2\text{Cl}$, reacts with $\text{NaOH}$ to form an unsaturated compound, $\text{C}_2\text{H}_3\text{Cl}$, as shown in reaction 7: $\text{ClCH}_2\text{CH}_2\text{Cl} + \text{NaOH} \rightarrow \text{C}_2\text{H}_3\text{Cl} + \text{H}_2\text{O} + \text{NaCl}$. State what is meant by unsaturated.

(c(ii))[1]

State the conditions for reaction 7.

(d(i))[1]

Compound $\textbf{D}$ contains only carbon, hydrogen and chlorine. Fig. 1.2 shows the mass spectrum of $\textbf{D}$. Explain the relative abundance of peaks 1 and 2 in the mass spectrum in Fig. 1.2.

(d(ii))[1]

Suggest the structure of $\textbf{D}$.

Worked solution & mark scheme

This 17-mark question has a full step-by-step worked solution and mark scheme. One marking point: Oxidation states correctly given as $+3$ (III) and $-1$ (I)

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