P6C.3 Although the hydrogen electrode may be conceptually the simplest electrode and is the basis for the choice of reference potential in electrochemical systems, it is cumbersome to use. Therefore, several substitutes for it have been devised. One of these alternatives is the quinhydrone electrode (quinhydrone, Q.QH,, is a complex of quinone, CH,O, Q, and hydroquinone, C,H,O,H,= QH₂), where the concentrations of Q-QH₂ and QH, are equal to each other. The electrode half-reaction is Q(aq) + 2H(aq) + 2e → QH2(aq), E = +0.6994 V. If the cell = Hg(s) Hg,Cl(s) HCl(aq)|Q QH₂|Au(s) is prepared, and the measured cell potential is +0.190 V, what is the pH of the HCl solution?