The reaction; 12H2(g) + AgCl(s) H+(aq) + Cl-(aq) + Ag(s) occurs in which of the following galvanic cell :
- Pt | H2(g) | HCl(soln.) | AgNO3(aq) | Ag
- Ag | AgCl(s) | KCl(soln.) | AgNO3(aq.) | Ag
- Pt | H2(g) | KCl(soln.) | AgCl(s) | Ag
- Pt | H2(g) | HCl(soln.) | AgCl(s) | Ag
Answer
(4) Pt | H2(g) | HCl(soln.) | AgCl(s) | Ag
Solution
Anode (oxidation): 12H2(g) H+(aq) + e-, a hydrogen electrode Pt | H2 | H+.
Cathode (reduction): AgCl(s) + e- Ag(s) + Cl-(aq), a metal–insoluble salt electrode Cl- | AgCl | Ag.
Since the reaction forms H+ and Cl- in one solution, the common electrolyte is HCl: Pt | H2 | HCl | AgCl | Ag, so (D) is correct.
(A): the cathode is Ag+/Ag with no AgCl, so (A) is wrong.
(B): there is no hydrogen electrode, so (B) is wrong.
(C): KCl solution has no H+ for the H+/H2 electrode, so (C) is wrong.
Answer: (4)