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

Light can be converted into electricity with the help of a ......... .

Given that
$E^o_{Ni^{2+} | Ni} = -0.25 \ V$
$E^o_{Cu^{2+} | Cu} = 0.34 \ V$
$E^o_{Ag^{+} | Ag} = 0.80 \ V$
$E^o_{Zn^{2+} | Zn} = -0.76 \ V$
Which of the following reactions under standard condition will not take place in the specified direction?

Based on the reaction $\frac{4}{3} \, Al + O_2 \to \frac{2}{3} \, Al_2O_3$,with $\Delta G = -827 \, kJ \, mol^{-1}$ of $Al_2O_3$,what is the minimum $e.m.f.$ required for the electrolysis? $(F = 96500 \, C \, mol^{-1})$

The Gibbs energy change (in $J$) for the given reaction at $[Cu^{2+}] = [Sn^{2+}] = 1 \, M$ and $298 \, K$ is:
$Cu_{(s)} + Sn^{2+}_{(aq)} \rightarrow Cu^{2+}_{(aq)} + Sn_{(s)}$
$(E^{\circ}_{Sn^{2+}|Sn} = -0.16 \, V, E^{\circ}_{Cu^{2+}|Cu} = 0.34 \, V, F = 96500 \, C \, mol^{-1})$

Identify the anode,cathode,positive electrode,and negative electrode for the $Daniell$ cell $(Zn-Cu)$ and the $Copper-Silver$ $(Cu-Ag)$ cell.