# Predict the products of electrolysis

## Homework Statement

What products are expected in the electrolysis of CuBr2(aq)?

## The Attempt at a Solution

This is actually a solved example from my textbook that I have a question about. It says to first consider the possible reactions at the cathode.

Since reduction happens at the cathode, it says the possible reductions are:
Cu2+(aq) + 2e- --> Cu(s) E = +0.34
2H2O(l) + 2e- --> H2(g) + 2OH- E= -0.83

The first one happens because its E is the most positive.

What I'm wondering is why we didn't include the reduction of Br2. Is it because Br- is an anion that we don't consider it?

And, how did they know to use the reaction for water that I gave and not 2H20(l) --> O2(g) + 4H+ + 4e-? (Because it's oxidation, which can't happen at the cathode, right?)

Borek
Mentor
What I'm wondering is why we didn't include the reduction of Br2.

Because there is no Br2?

Wouldn't you get the dissociation of CuBr2 --> Cu2+ + 2Br-

And so need to take into account that 2Br2- + 2e- --> Br2? Why can't that be happening at the cathode?

symbolipoint
Homework Helper
Gold Member
What does a Standard Reduction Table tell you about
Br2 + 2e- -------> 2Br- ?
Note that you are interested in the oxidation, not the reduction.

It has a value of +1.07.

But I don't understand what that means for this problem =(

There's something I'm missing here...

symbolipoint
Homework Helper