Question

An electrochemical cell consists of a standard hydrogen electrode and a copper metal electrode. a. What is the potential of the cell at 25°C if the copper electrode is placed in a solution in which = 3.8 x 10-4 M? Ecell = V b. The copper electrode is placed in a solution of unknown (Cu?+]. The measured potential at 25°C is 0.206 v. What is (cu?+]? (Assume Cu²+ is reduced.) [Cu²+] = M

Answer 1

In a cell containing copper and Hydrogen electrode, Copper will be the cathode and Hydrogen electrode will be the anode.

A.

At anode,            H₂ (g) ------->2H⁺ + 2e^-

At Cathode,        Cu²⁺(aq) +2e^- ---> Cu (s)

Cell reaction       Cu²⁺(aq) + H₂ (g) --------> 2H⁺ + Cu (s)

[Cu²⁺] = 3.8 x 10^-4M (given)

E0 = 0.34V

Nernst equation is given by

E = E0- (0.0592/n) log {[H+]²/[Cu²⁺]}

E = 0.34 – (0.0592/2) Log{1/3.8 x 10^-4M}

E = 0.23876 V

B.

E = E0- (0.0592/2) log {[H+]²/[Cu²⁺]}

E = 0.206 V (given)

0.206 = 0.34 + 0.0296 log[Cu²⁺]

log[Cu²⁺] = -4.4966

[Cu²⁺] = 3.186 x 10^-5 M