For the reaction $Cr_2O_7^{2-} + I^- \to I_2 + Cr^{3+}$,if $E_{cell}^o = 0.79 \ V$ and $E_{Cr_2O_7^{2-}}^o = 1.33 \ V$,then $E_{I_2}^o = $ ............. $V$.

Consider the following cell:
$Zn_{(s)} \mid Zn^{2+}_{(1M)} \parallel KCl_{(sat)} \mid Hg_2Cl_{2(paste)} \mid Hg$
$E^{\circ}_{cell} = 1.007 \ V$ and $E^{\circ}_{calomel} = 0.242 \ V$
What is the standard potential of $Zn$ (in $V$)?

For the spontaneity of a cell,which of the following is correct?

If $E^o_{A^{+2}/A} = -0.30 \ V$ and $E^o_{A^{+3}/A^{+2}} = 0.40 \ V$,the standard $EMF$ of the reaction: $A + 2A^{+3} \to 3A^{+2}$ will be ............ $V$.

For the spontaneity of a cell,which of the following is correct?

The formal potential of $Fe^{3+}/Fe^{2+}$ in a sulphuric acid and phosphoric acid mixture $(E^{\circ}=+0.61 \ V)$ is much lower than the standard potential $(E^{\circ}=+0.77 \ V)$. This is due to