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

Chemistry of transition elements — practice question

In aqueous solution, copper(II) salts contain the blue [Cu(H2O)6]2+ complex ion. Separate samples of this blue solution are then treated with aqueous sodium hydroxide and with concentrated hydrochloric acid.
(a)[6]

Provide the following details for each reaction. 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 with 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 fully hydrolysed by water. Every chlorine atom present in the sulfur chloride is converted into chloride ions. The solution is made up 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 uses $22.40\,\text{cm}^3$ of $0.0500\,\text{mol dm}^{-3}\,\text{AgNO}_3\text{(aq)}$. Calculate the empirical formula of the sulfur chloride. 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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