The reaction is spontaneous if the cell potential is

The standard electrode potentials of two half-cells are given as: $Ni^{2+}_{(aq)} + 2e^{-} \rightarrow Ni_{(s)}$; $E^o = -0.25 \ V$ and $Zn^{2+}_{(aq)} + 2e^{-} \rightarrow Zn_{(s)}$; $E^o = -0.76 \ V$. What is the standard $emf$ of the cell formed by connecting these two half-cells in $volt$?

The $E^{0}_{Red}$ values for $Li, Zn, H,$ and $Ag$ are $-3.05 \ V, -0.76 \ V, 0.00 \ V,$ and $0.80 \ V$ respectively. Which of these has the highest reducing power?

The standard electrode potentials for some half-reactions are given below. Which statement is correct?
$(A) Sn^{4+} + 2e^{-} \rightarrow Sn^{2+}, E^o = +0.15 \ V$
$(B) 2Hg^{2+} + 2e^{-} \rightarrow Hg_{2}^{2+}, E^o = +0.92 \ V$
$(C) PbO_2 + 4H^{+} + 2e^{-} \rightarrow Pb^{2+} + 2H_2O, E^o = +1.45 \ V$

The $(\frac{\partial E}{\partial T})_P$ of different types of half cells are as follows:

$A$	$B$	$C$	$D$
$1 \times 10^{-4}$	$2 \times 10^{-4}$	$0.1 \times 10^{-4}$	$0.2 \times 10^{-4}$

(Where $E$ is the electromotive force)
Which of the above half cells would be preferred to be used as reference electrode?

At ${25 \, ^\circ C}$,the standard reduction potentials for $Li^+/Li$,$Ba^{2+}/Ba$,$Na^+/Na$,and $Mg^{2+}/Mg$ are $-3.05 \, V$,$-2.73 \, V$,$-2.71 \, V$,and $-2.36 \, V$ respectively. Which of the following is the strongest oxidizing agent?