Which among the following is an example of a metal-metal ion electrode?

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

Which of the following statements is incorrect during the discharge of a lead storage battery?

For the reaction $2 Fe^{3+}_{(aq)} + 2 I^{-}_{(aq)} \rightarrow 2 Fe^{2+}_{(aq)} + I_{2(s)}$,the magnitude of the standard molar free energy change,$\Delta_{r} G_{m}^{\circ} = -$ ........... $kJ$ (Round off to the Nearest Integer). $\left[ E_{Fe^{2+} / Fe_{(s)}}^{\circ} = -0.440 \ V; \ E_{Fe^{3+} / Fe_{(s)}}^{\circ} = -0.036 \ V; \ E_{I_{2} / 2I^{-}}^{\circ} = 0.539 \ V; \ F = 96500 \ C \ mol^{-1} \right]$

$A$ variable,opposite external potential $(E_{ext})$ is applied to the cell $Zn | Zn^{2+} (1 \ M) || Cu^{2+} (1 \ M) | Cu$ of potential $1.1 \ V$. When $E_{ext} < 1.1 \ V$ and $E_{ext} > 1.1 \ V$,respectively,electrons flow from:

Colourless solutions of the following four salts are placed separately in four different test tubes and a strip of copper is dipped in each one of these. Which solution will turn Blue?