CBSE Class 10 Science 2019 · Paper 31/2/3 · Question 10

(i) Roasting: $2{\text{Cu}}_2\text{S}+3{\text{O}}_2\stackrel{\text{heat}}{\to }2{\text{Cu}}_2\text{O}+2{\text{SO}}_2$ (ii) Reduction of copper(I) oxide by copper(I) sulphide: $2{\text{Cu}}_2\text{O}+{\text{Cu}}_2\text{S}\stackrel{\text{heat}}{\to }6\text{Cu}+{\text{SO}}_2$ (iii) Electrolytic refining (impure copper as the anode, a thin strip of pure copper as the cathode, acidified copper sulphate solution as the electrolyte): at the anode, $\text{Cu}\to {\text{Cu}}^{2+}+2e^{-}$; at the cathode, ${\text{Cu}}^{2+}+2e^{-}\to \text{Cu}$.