Chemistry 9701 · AS & A Level · Chemistry of transition elements

Chemistry of transition elements — practice question

Blue aqueous copper(II) salt solutions contain the $[\text{Cu(H}_2\text{O)}_6]^{2+}$ complex, and separate samples of this blue solution are treated with aqueous sodium hydroxide and with concentrated hydrochloric acid.
(a)[6]

For each of these reactions, provide the following details. • reaction with aqueous sodium hydroxide: ionic equation; type of reaction; colour and state of the copper-containing product. • reaction with concentrated hydrochloric acid: ionic equation; type of reaction; colour and state of the copper-containing product.

(b)[3]

Chloride ions may be tested for using aqueous silver nitrate, $\text{AgNO}_3\text{(aq)}$. $\text{Ag}^+\text{(aq)} + \text{Cl}^-\text{(aq)} \rightarrow \text{AgCl(s)}$ $0.303\,\text{g}$ of a sulfur chloride is completely hydrolysed with water. Every chlorine atom present in the sulfur chloride is changed into chloride ions. The solution is diluted to $100.0\,\text{cm}^3$. A $25.00\,\text{cm}^3$ portion of this solution is titrated with $0.0500\,\text{mol dm}^{-3}\,\text{AgNO}_3\text{(aq)}$. The titration requires $22.40\,\text{cm}^3$ of $0.0500\,\text{mol dm}^{-3}\,\text{AgNO}_3\text{(aq)}$. Calculate the empirical formula of the chloride of sulfur. Show all your working.

Worked solution & mark scheme

This 9-mark question has a full step-by-step worked solution and mark scheme. One marking point: $[Cu(H_2O)_6]^{2+} + 2OH^- \rightarrow Cu(OH)_2 + 6H_2O$

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