(Solved): An Ag/AgCl electrode dipping into \( 1.00 \mathrm{M} \mathrm{HCl} \) has a standard reduction poten ...

An Ag/AgCl electrode dipping into \( 1.00 \mathrm{M} \mathrm{HCl} \) has a standard reduction potential of \( +0.2223 \mathrm{~V} \). The half-reaction is \( \mathrm{AgCl}(\mathrm{s})+\mathrm{e}^{\prime} \rightleftharpoons \mathrm{Ag}(\mathrm{s})+\mathrm{Cl}(\mathrm{aq}) \) A second \( \mathrm{Ag} / \mathrm{AgCl} \) electrode is dipped into a solution containing \( \mathrm{Cl} \) at an unknown concentration. The cell generates a potential of \( 0.0398 \mathrm{~V} \), with the electrode in the solution of unknown concentration having a negative charge. What is the molar concentration of \( \mathrm{Cl} \) in the unknown solution? \( \left[\mathrm{Cl}^{-}\right]= \)