Consider a galvanic cell consisting of a Zn(s) | Zn^{2+}(aq, 1.0 M) half-cell and a hydrogen half-cell (Pt | H_{2}(g, 1 atm) | H^{+}(aq, 1.0 M)) connected by a KCl(aq) salt bridge.
After the cell has been producing current for several minutes, predict whether the pH of the hydrogen half-cell increases, decreases, or remains approximately constant, and briefly justify your prediction.