electrochemistry Questions

Given below are half cell reactions:${\text{MnO}}_4^{-}+8{\text{H}}^{+}+5e^{-}\to {\text{Mn}}^{2+}+4{\text{H}}_2\text{O},E_{{\text{MnO}}_4^{-}/{\text{Mn}}^{2+}}^{\circ }=+1.510\text{V}$$\frac{1}{2}{\text{O}}_2+2{\text{H}}^{+}+2e^{-}\to {\text{H}}_2\text{O},E_{{\text{O}}_2/{\text{H}}_2\text{O}}^{\circ }=+1.223\text{V}$ Will the permanganate ion, ${\text{MnO}}_4^{-}$, liberate ${\text{O}}_2$ from water in the presence of an acid?

At $298\text{K}$, the standard electrode potentials of ${\text{Cu}}^{2+}/\text{Cu},{\text{Zn}}^{2+}/\text{Zn},{\text{Fe}}^{2+}/\text{Fe}$ and ${\text{Ag}}^{+}/\text{Ag}$ are $0.34\text{V},-0.76\text{V},-0.44\text{V}$ and $0.80\text{V}$, respectively. On the basis of standard electrode potential, predict which of the following reaction cannot occur?

Find the emf of the cell: $\text{Ni}(s)+2{\text{Ag}}^{+}(0.001\text{M})\to {\text{Ni}}^{2+}(0.001\text{M})+2\text{Ag}(s)$ [Given that $E_{cell}^{\circ }=1.05\text{V}$, $\frac{2.303RT}{F}=0.059$ at $298\text{K}$ ]