Saturated solution of $KNO_3$ is used to make a 'salt-bridge' because:

If the standard $emf$ of the cell $Zn_{(s)} | Zn_{(1 \ M)}^{+2} || Ag_{(1 \ M)}^{+1} | Ag_{(s)}$ is $1.55 \ V$, what is the electrical work done under standard conditions (in $kJ$)?

Copper cannot replace $.....$ from its solution.

Some statements about Leclanché cell are:
$(I)$ Anode is zinc metal
$(II)$ Cathode is graphite rod surrounded by powdered $MnO_2$ and carbon
$(III)$ Electrolyte is a moist paste of $ZnO$ and $KOH$
$(IV)$ Oxidation product is $ZnO$
The correct statements are:

Standard electrode potentials for a few half cells are mentioned below:
$E^0_{Cu^{2+}/Cu} = 0.34 \ V, E^0_{Zn^{2+}/Zn} = -0.76 \ V$
$E^0_{Ag^{+}/Ag} = 0.80 \ V, E^0_{Mg^{2+}/Mg} = -2.37 \ V$
Which one of the following cells gives the most negative value of $\Delta G^0$?

Calculate $\Delta_r G^o$ for the cell reaction:
$Zn_{(s)} + Cu^{2+}_{(aq)} \to Zn^{2+}_{(aq)} + Cu_{(s)}$
Given: $E^o_{Cu^{2+}/Cu} = 0.34 \, V, E^o_{Zn^{2+}/Zn} = -0.76 \, V$