The standard reduction potentials of $4$ elements are given below. Which of the following will be the most suitable reducing agent?
$I = -3.04 \ V$
$II = -1.90 \ V$
$III = 0 \ V$
$IV = 1.90 \ V$

$E^o_{cell}$ 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 $0.06$)

The standard electrode potentials $\left( E_{M^{+}/M}^\circ \right)$ of four metals $A, B, C$ and $D$ are $-1.2 \ V, 0.6 \ V, 0.85 \ V$ and $-0.76 \ V$,respectively. The sequence of deposition of metals on applying potential is

Consider the following standard electrode potentials ($E^0$ in volts) in aqueous solution. Based on this data,which of the following statements is correct?

Element	$M^{3+}/M$	$M^{+}/M$
$Al$	$-1.66$	$+0.55$
$Tl$	$+1.26$	$-0.34$

Which of the following metals will not release $H_{2(g)}$ upon reaction with an acid?

Consider the cell given below:
$Ag_{(s)} | Ag^{\oplus} || Cu^{2+} | Cu_{(s)}$
Given:
$Ag^{\oplus} + e^{-} \to Ag; E^{o} = x$
$Cu^{2+} + 2e^{-} \to Cu; E^{o} = y$
The value of $E^{o}_{cell}$ is: