A sample of water has a hardness expressed as $77.5 \mathrm{ppm}$ ${\mathrm{Ca}}^{2+}$. This sample is passed through an ion exchange column and the ${\mathrm{Ca}}^{2+}$ is replaced by ${\mathrm{H}}^{+}$. Select the correct statement(s).

Which of the following expression(s) represent the voltage of cell at $298 \mathrm{K}?$

$\mathrm{Ag}\left(\mathrm{s}\right)\left|\mathrm{Ag}\right|$ (saturated solution) $\overline{)|{\mathrm{Ag}}_2{\mathrm{C}}_2{\mathrm{O}}_4}$ (saturated solution) $\overline{)\mathrm{Ag} \left(\mathrm{s}\right)}$

In the following electrochemical cell: $\mathrm{Pt} \overline{) {\mathrm{H}}_2} \left(\mathrm{x} \mathrm{atm}\right) \overline{) {\mathrm{H}}^{+} }\left(\mathrm{pH}=\mathrm{y}\right) \Vert {\mathrm{Zn}}^{2+} \left(\mathrm{z} \mathrm{M}\right) \overline{) \mathrm{Zn}}$

${\mathrm{E}}_{\mathrm{cell}}^{\mathrm{o}}={\mathrm{E}}_{\text{cell }}.$ This will be possible when