# Homework Help: Electrochemistry of galvanic couple in an acidic solution

1. Oct 22, 2009

### kamilio

1. The problem statement, all variables and given/known data
From the perspective of corrosion...Gold and Copper II are joined together and immersed in a 1Molar HCl solution. What possible half-cell reactions and full cell reactions can occur? Which one is most likely to proceed?

2. Relevant equations
Half-cell potentials for
$$Au^{3+} + 3e^- \rightarrow Au(s) = 1.5V$$
$$Cl_2(g) + 2e^- \rightarrow 2Cl^- = 1.36V$$
$$Cu^{2+} + 2e^- \rightarrow Cu(s)=0.34V$$
$$2H^+ + 2e^- \rightarrow H_2(g)=0V$$

3. The attempt at a solution
The metals are exposed to hydrogen and chloride ions. Gold is the most noble and will not oxidize. The hydrogen will not oxidize copper because copper is cathodic wrt hydrogen. For the same reason, hydrogen cannot oxidize gold. Gold will oxidize copper but I don't know the hydrogen ions will steal the incoming electrons from copper and reduce to hydrogen gas.

Last edited: Oct 22, 2009
2. Oct 22, 2009

### kamilio

Can someone please assist me here. It's a rather simple problem but I just can't sort it through.

Hydrogen cannot oxidize gold or copper because it is lower on the emf series. Also, copper and gold cannot react because there are no Au ions in the solution (only H+ and Cl-) right? So then there aren't any half-cell/full-cell reactions?