Question

Attempt either (a) or (b): **(a)** (i) Write the balanced chemical equations involved in the extraction of: (I) $Hg$ from $HgS$ (II) $Zn$ from $ZnCO_3$ (III) $Na$ from $NaCl$ (ii) Why does sodium chloride: (I) not conduct electricity in solid state? (II) have very high melting point? **OR** **(b)** During extraction of metals, electrolytic refining is used to obtain pure metals. (i) Which material will be used as cathode and anode for refining of zinc metal by this process? (ii) Name the electro

Accepted Answer

0. **Part (a):** (i) (I) $2HgS + 3O_2 \xrightarrow{\Delta} 2HgO + 2SO_2$, $2HgO \xrightarrow{\Delta} 2Hg + O_2$ (II) $ZnCO_3 \xrightarrow{\Delta} ZnO + CO_2$, $ZnO + C \rightarrow Zn + CO$ (III) Electrolysis of molten $NaCl$: At cathode $Na^+ + e^- \rightarrow Na$ (ii) (I) Ions are held in fixed positions in solid lattice; (II) Strong electrostatic ionic bonds require huge heat energy to break. **Part (b):** (i) Anode: Impure Zinc; Cathode: Pure Zinc strip. (ii) Electrolyte: Acidified Zinc sulphate solution ($ZnSO_4$). Pure zinc deposits at the cathode. (iii) Zinc acts as a protective barrier and sacrificial anode (Galvanization).

Extraction and Refining of Metals

Explanation

Practise this under board exam conditions