The cell potential of a cell in operation is

What is denoted by a negative $E^o$ and a positive $E^o$ value in electrochemistry?

The electrode potential for $M^{2+}_{(aq)} + e^- \rightarrow M^{+}_{(aq)}$ and $M^{+}_{(aq)} + e^- \rightarrow M_{(s)}$ are $+0.15 \text{ V}$ and $+0.50 \text{ V}$ respectively. The value of $E^\circ_{M^{2+}/M}$ will be: (in $\text{ V}$)

The $EMF$ of the cell $Ni | Ni^{2+} (1.0 \ M) || Au^{3+} (1.0 \ M) | Au$ is ............ $V$. (Given: $E^o_{Ni^{2+}/Ni} = -0.25 \ V$; $E^o_{Au^{3+}/Au} = 1.50 \ V$)

What is standard electrode potential?

The $emf$ of a galvanic cell constituted with the electrodes $Zn^{2+} | Zn$ $(-0.76 \ V)$ and $Fe^{2+} | Fe$ $(-0.41 \ V)$ is