Chemistry 9701 · AS & A Level · Atoms, molecules and stoichiometry

Atoms, molecules and stoichiometry — practice question

Phosphorus is a reactive element in Period 3.
(a(i))[3]

Both white phosphorus and red phosphorus contain covalent bonding. Suggest the kinds of structure shown by white phosphorus ($\text{P}_4$) and red phosphorus ($\text{P}$). Explain why red phosphorus ($\text{P}$) has a higher melting point than white phosphorus ($\text{P}_4$).

(a(ii))[1]

Red phosphorus ($\text{P}$) is produced when white phosphorus ($\text{P}_4$) is exposed to sunlight. $\frac{1}{4}\text{P}_4(s) \rightarrow \text{P}(s)$ \quad $\Delta H = -17.6\ \text{kJ mol}^{-1}$ Use this information to draw a reaction pathway diagram showing the conversion of white phosphorus ($\text{P}_4$) into red phosphorus ($\text{P}$).

(b(i))[1]

State the oxidation number for phosphorus in $\text{P}_4\text{O}_{10}$.

(b(ii))[2]

Deduce the identity of $Q$ and hence write chemical equations for reactions 1 and 2. reaction 1: $\text{PCl}_5 + \ldots \text{H}_2\text{O} \rightarrow \ldots$ reaction 2: $\text{P}_4\text{O}_{10} + \ldots \text{H}_2\text{O} \rightarrow \ldots$

(c(i))[1]

Give the empirical formula for triphenylphosphine.

(c(ii))[2]

State the reaction types occurring in stages 1 and 2. Stage 1: $\ldots$ Stage 2: $\ldots$

(c(iii))[2]

Draw the structures for $G$ and $H$ in the boxes provided.

(d)[2]

Identify the organic products produced when compound $J$, shown, is heated with hot concentrated acidified manganate(VII) ions.

Worked solution & mark scheme

This 14-mark question has a full step-by-step worked solution and mark scheme. One marking point: Phosphorus(IV) oxide has a simple molecular structure

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