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General Chemistry

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Using Cell Potential of pH Meter to Determine pH of Solution

CHEM-B1J4OL

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.

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

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