Which substance is used as cathode in a mercury cell?

Upon dipping a copper rod into an aqueous solution of the salt,the solution that turns blue is

Given the data at $25\, ^oC$:
$Ag + I^{-} \rightarrow AgI + e^-$,$E^o = 0.152\, V$
$Ag \rightarrow Ag^{+} + e^-$,$E^o = -0.800\, V$
What is the value of $\log K_{sp}$ for $AgI$? $(2.303\, RT/F = 0.059\, V)$

The reaction $\frac{1}{2} H_{2(g)} + AgCl_{(s)} \rightleftharpoons H^{+}_{(aq)} + Cl^{-}_{(aq)} + Ag_{(s)}$ occurs in which of the given galvanic cell?

Which statement is correct for a fuel cell?

In a dry cell,the reaction which takes place at the zinc anode is: