Identify the substance underlined in each of the following:
(i) The electrode that increases in mass during the electro-refining of silver.
(ii) The acid that is a dehydrating as well as a drying agent.
(iii) The catalyst used to oxidize ammonia into nitric oxide.
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(i) Cathode
Reason — Pure copper is deposited on the thin sheet of pure copper placed at the cathode
(ii) Sulphuric acid
Reason — Being hygroscopic sulphuric acid absorbs moisture but not enough to form a solution. Hence, it is a drying agent.
Sulphuric acid is a dehydrating agent as it can remove chemically combined water molecules from blue vitriol.
CuSO4.5H2O + H2SO4 ⇌ CuSO4 + 5H2O
(iii) Platinum
$4\text{NH}_3 + 5\text{O}_2 \xrightarrow[800 ^{\circ} \text{C}]{\text{Pt.}} \text{4NO} + \text{6H}_\text{2}\text{O} + \Delta$