General Chemistry

Free Version

Upgrade subject to access all content


Using Cell Potential of pH Meter to Determine pH of Solution


pH meters utilize cell potential to determine the concentration of $\textrm{H}^+$ ions. Consider a pH probe that uses a $\textrm{Ag}$ electrode in $1 \textrm{ M HCl}$ solution in a glass tube (one compartment of the cell) with a glass frit (salt bridge) immersed in a solution. The half reactions used by a pH meter are below.

$$\textrm{Ag}_{(s)}+ \textrm{Cl}^-_{(aq)}\rightarrow \textrm{AgCl}_{(s)} +e^-\qquad E°=0.222\textrm{ V}$$

$$2\textrm{H}^+_{(aq)} + 2e^- \rightarrow \textrm{H}_{2(g)} \qquad E°=0.00\textrm{ V}$$