(A) Write plausible chemical equations to represent the 

(a) Roasting of Cu₂S;

(b) Reduction of WO₃ with H₂(g);

(c) Thermal decomposition of HgO to its elements.

(B) Write chemical equations to represent the 

(a) Reduction of Cr₂O₃ to chromium with silicon as the reducing agent; 

(b) Conversion of Co(OH)₃(s) to Co₂O₃(s) by roasting; 

(c) Production of pure MnO₂(s) from MnSO₄(aq) at the anode in an electrolysis cell.