The $e.m.f.$ of the following galvanic cells are represented by $E_1, E_2, E_3$ and $E_4$. Which of the following statements is true?
$(i)$ $Zn|Zn^{2+} (1 \, M)||Cu^{2+} (1 \, M)|Cu$
$(ii)$ $Zn|Zn^{2+} (0.1 \, M)||Cu^{2+} (1 \, M)|Cu$
$(iii)$ $Zn|Zn^{2+} (1 \, M)||Cu^{2+} (0.1 \, M)|Cu$
$(iv)$ $Zn|Zn^{2+} (0.1 \, M)||Cu^{2+} (0.1 \, M)|Cu$

The following reaction takes place at $298 \, K$ in an electrochemical cell involving two metals $A$ and $B$,
$A^{2+}_{(aq)} + B_{(s)} \rightarrow B^{2+}_{(aq)} + A_{(s)}$
with $[A^{2+}] = 4 \times 10^{-3} \, M$ and $[B^{2+}] = 2 \times 10^{-3} \, M$ in the respective half-cells,the cell $EMF$ is $1.091 \, V$.
The equilibrium constant of the reaction is closest to

$E_{1}$,$E_{2}$ and $E_{3}$ are the emfs of the following three galvanic cells respectively.

The standard $emf$ of a galvanic cell involving $3$ moles of electrons in its redox reaction is $0.59 \ V$. The equilibrium constant for the reaction of the cell is:

For the cell $Zn_{(s)} | Zn^{2+} (0.1 \ M) || Fe^{2+} (0.01 \ M) | Fe_{(s)}$ at $298 \ K$,$E_{cell} = 0.2905 \ V$. What is the equilibrium constant $(K_c)$ for the reaction $Zn_{(s)} + Fe^{2+}_{(aq)} \rightleftharpoons Zn^{2+}_{(aq)} + Fe_{(s)}$?

At $298 \ K$,some standard electrode potentials are given below:

$Pb^{2+} / Pb$	$-0.13 \ V$
$Ni^{2+} / Ni$	$-0.24 \ V$
$Cd^{2+} / Cd$	$-0.40 \ V$
$Fe^{2+} / Fe$	$-0.44 \ V$

Metal rods $X$ and $Y$ are inserted into a solution containing $0.001 \ M$ $X^{2+}$ and $0.1 \ M$ $Y^{2+}$ at $298 \ K$ and connected by a conducting wire. This results in the dissolution of $X$. The correct combination$(s)$ of $X$ and $Y$ are,respectively:
(Given: Gas constant,$R = 8.314 \ J \ K^{-1} \ mol^{-1}$,Faraday constant,$F = 96500 \ C \ mol^{-1}$)
$(A) \ Cd$ and $Ni \ \ (B) \ Cd$ and $Fe \ \ (C) \ Ni$ and $Pb \ \ (D) \ Ni$ and $Fe$