mass of Zn rod = 23.725 g, molarity of SO₄^2- remains same.

Dry cell (Leclanche cell) consists of a zinc container which acts as anode and cathode is a carbon rod surrounded by powdered manganese dioxide and carbon. The space between the electrodes is filled by a moist paste of NH₄ CI and ZnCl₂
The reactions are:
At anode \(Zns\rightarrow Zn^{ 2+ }(aq)+2e^{ - }\)
At cathode 
\(2e^{ - }+2NH^{ + }_{ 4 }(aq)\rightarrow 2NH_{ 3 }(g)+H_{ 2 }(g)\)
\(2NH_{ 3 }(g)+Zn^{ 2+ }(aq)\rightarrow 2NH_{ 3 }(g)+H_{ 2 }(g)\)
Overall reaction
\(Zn(s)+2NH^{ + }_{ 4 }(aq)+MnO_{ 2 }(s)\rightarrow \left[ Zn(NH_{ 3 }) \right] ^{ 2+ }(aq)+Mn_{ 2 }O_{ 3 }(s)+H_{ 2 }O(l)\)
By using Nernst equation,
\(E_{ cell }=E^{ 0 }_{ cell }-\frac { 2.303RT }{ nF } in\frac { \left[ Zn(NH_{ 3 } \right] ^{ 2+ } }{ \left[ NH^{ + }_{ 4 } \right] } \)
Due to the presence of ions in the overall reaction, its voltage decreases with time.

\(\begin{aligned} \mathrm{Zn}(s)+\mathrm{Cu}^{2+}(a q) \longrightarrow & \mathrm{Zn}^{2+}(a q)+\mathrm{Cu}(s) \end{aligned}\)
\(\begin{aligned} E^{\circ} & =+1.1 \mathrm{~V}, \Delta G^{\circ}=? \end{aligned}\)
\(\begin{aligned} 1 \mathrm{~F} & =96500 \space \mathrm{C} \space \mathrm{mol}^{-1}, n=2 \end{aligned}\)
\(\begin{aligned} \Delta G^{\circ} & =-n F E^{\circ} \end{aligned}\)
\(\begin{aligned} =-2 \times 96500 \times 1.1=-212300 \mathrm{~J} \mathrm{~mol}^{-1} \end{aligned}\)

\({ \wedge }^{ ° }\left[ { Al }_{ 2 }{ \left( { SO }_{ 4 } \right) }_{ 3 } \right] =2{ \lambda }^{ ° }\left( { Al }^{ 3+ } \right) +3{ \lambda }^{ ° }\left( { { SO }_{ 4 } }^{ 2- } \right)\)
\({ \wedge }^{ ° }\left[ { Al }_{ 2 }{ \left( { SO }_{ 4 } \right) }_{ 3 } \right] =858S{ cm }^{ 2 }{ mol }^{ -1 },\)
\( { \lambda }^{ ° }\left( { { SO }_{ 4 } }^{ 2- } \right) =106S{ cm }^{ 2 }{ mol }^{ -1 }\)
\(\therefore \ 858=2{ \lambda }^{ ° }\left( { Al }^{ 3+ } \right) +3\times 160\)
\(\\ or \ 2{ \lambda }^{ ° }\left( { Al }^{ 3+ } \right) =858-480=378\)
\(\therefore \ { \lambda }^{ ° }\left( { Al }^{ 3+ } \right) =\frac { 378 }{ 2 } =189S{ cm }^{ 2 }{ mol }^{ -1 }\)

Conductivity is the conductance of a solution of 1 cm length and having 1 sq.cm as the area of cross-section i.e., of one-centimeter cube.
Direct current results in the electrolysis of the electrolytic solution. As a result, the concentration of the electrolyte near the electrodes changes and these result change in the resistance of the solution.

Mg, Al, Zn, Fe, Cu, Ag

\(k=G\times \frac { 1 }{ a } =\frac { 1 }{ R } \frac { 1 }{ a } ,i.e.,k \ \infty \frac { 1 }{ R } \) Hence, B will offer greater resistance.

\(\frac { { W }_{ Ag } }{ Eq.wt \ of \ Ag } =\frac { { W }_{ Au } }{ Eq.wt \ of \ Au } \)
Eq.wt. of Ag = 108, Eq.wt. of Au = \(\frac{197}{3}\)
\(\frac{0.583}{108}\)= \(\frac { { W }_{ Au } }{ \frac { 197 }{ 3 } } \), W_Au = \(\frac { 0.583\times 197 }{ 108\times 3 } \)= 0.354 g

Fuel cells are those cells in which chemical energy of fuel is converted into electrical energy. In both cells chemical energy is converted into electrical energy. The efficiency of fuel cell is higher than that of galvanic cell.