(a) (i)Name the class of oxides to which copper (II) oxide belongs. (ii) Give the reason why copper (II) oxide increases in mass on exposure to the atmosphe...
Question 1 Report
(a) (i)Name the class of oxides to which copper (II) oxide belongs.
(ii) Give the reason why copper (II) oxide increases in mass on exposure to the atmosphere
(iii) Write an equation to show the action of dilute hydrochloric acid on copper (II) oxide.
(b) List two methods of removing total hardness from water.
Answer Details
(a)(i) Copper(II) oxide, \(CuO\), is a basic oxide (a metallic oxide that reacts with acids to give salt and water only).
(ii) Copper(II) oxide increases in mass on exposure to the atmosphere because, being a basic oxide, it slowly absorbs moisture (water vapour) and carbon(IV) oxide from the air, forming a basic copper carbonate/hydroxide. The added water and carbon(IV) oxide account for the gain in mass.
(iii) Action of dilute hydrochloric acid on copper(II) oxide:
\[CuO_{(s)} + 2HCl_{(aq)} \rightarrow CuCl_{2(aq)} + H_2O_{(l)}\]
(b) Two methods of removing total hardness (both temporary and permanent) from water:
- Addition of washing soda (sodium trioxocarbonate(IV), \(Na_2CO_3\)), which precipitates the calcium and magnesium ions as insoluble carbonates.
- Ion-exchange method (passing the water through a permutit/zeolite or ion-exchange resin), which replaces the \(Ca^{2+}\) and \(Mg^{2+}\) ions with sodium ions.
(Distillation of the water is also acceptable, as it leaves the dissolved salts behind.)
Download The App On Google Playstore
Everything you need to excel in your exams
