When does a cell reaction occur spontaneously?

$E^o_{cell}$ for the cell: $Pt_{(s)} | H_{2(g)} | HCOOH_{(aq)} || CH_3COOH_{(aq)} | H_{2(g)} | Pt_{(s)}$ at $25^oC$ is ............ $V$. ($K_a$ of $HCOOH = 2.4 \times 10^{-4}$,$K_a$ of $CH_3COOH = 1.8 \times 10^{-5}$,$\log 2 = 0.3$,$\log 3 = 0.477$,$\frac{2.303RT}{F} = 0.059$ or $0.06$)

Standard reduction potentials for the following reactions are :
$Fe^{3+} + 3e^{-} \rightarrow Fe ; E^{\circ}_{1} = -0.036 \ V$
$Fe^{2+} + 2e^{-} \rightarrow Fe ; E^{\circ}_{2} = -0.44 \ V$
What will be the standard electrode potential for
$Fe^{3+} + e^{-} \rightarrow Fe^{2+} (in $V$)?$

What is the standard cell potential for the cell $Zn | Zn^{2+} (1M) || Cu^{2+} (1M) | Cu$? Given $E^o$ for $Zn^{2+} | Zn = -0.76 \ V$ and $E^o$ for $Cu^{2+} | Cu = +0.34 \ V$.

Among $Mg$,$Cu$,$Fe$,and $Zn$,the metal that does not produce hydrogen gas in reaction with hydrochloric acid is:

The standard electrode potential for the Daniell cell is $1.1 \ V$. What will be the value of standard Gibbs energy for the reaction?
$Zn_{(s)} + Cu_{(aq)}^{2+} \rightarrow Zn_{(aq)}^{2+} + Cu_{(s)}$
$(1 \ F = 96487 \ C \ mol^{-1})$