One of the commonly used electrode is calomel electrode. Under which of the following categories, calomel electrode comes?

What pressure (bar) of $$\mathrm{H}_2$$ would be required to make emf of hydrogen electrode zero in pure water at $$25^{\circ} \mathrm{C}$$ ?

Identify the factor from the following that does not affect electrolytic conductance of a solution.

Alkaline oxidative fusion of $$\mathrm{MnO}_2$$ gives "A" which on electrolytic oxidation in alkaline solution produces B. A and B respectively are