Reference no: EM13180506
Processing math: 0%Careful measurements of the cell voltage of the cell Pt, H2 (g, 1 bar) | NaOH (aq, 0.0100 mol/kg), NaCl (aq, .011 mol/kg) | AgCl(s) | Ag have been reported. Among the data is the following information :
t( degree C) 20.0 25.0 30.0
E/V 1.04774 1.04864 1.04942
Calculate pKw at these temperatures, and the standard enthalpy and entropy for the autoionization of water at 25 C.
Hint: The cell reaction is H2 (g) + 2AgCl(s) --> 2Ag(s) + 2Cl- + 2H+(aq)
Write the Nernst equation for this reaction, and then replace the molality of H+ with a relation using Kw and the molality of OH-. Rearrange this expression to solve for pKw (=-logKw) in terms of the standard and measured cell potentials and the given molalities of the reagents. Once the pKw's at the three temperatures are determined, the Van't Hoff equation can be used to determine Delta H for the reaction, and from that Delta G, and Delta S can be calculated.