Predict the products of electrolysis

In summary, the products expected in the electrolysis of CuBr2(aq) are Cu(s) and Br2(g). This is because the reduction of Cu2+ to Cu(s) is more favorable than the reduction of H2O to H2(g), and there is no Br2 present. The standard reduction table shows that the reduction of Br2 to Br- is less favorable than the reduction of Cu2+ to Cu(s). Therefore, the overall redox reaction for the electrolysis of CuBr2(aq) involves the reduction of Cu2+ and the oxidation of Br- to produce Cu(s) and Br2(g) respectively.
  • #1
jumbogala
423
4

Homework Statement


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


Homework Equations





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?)
 
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  • #2
jumbogala said:
What I'm wondering is why we didn't include the reduction of Br2.

Because there is no Br2?
 
  • #3
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?
 
  • #4
What does a Standard Reduction Table tell you about
Br2 + 2e- -------> 2Br- ?
Note that you are interested in the oxidation, not the reduction.
 
  • #5
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...
 
  • #6
You would determine or calculate the E for any pair of halfcell reduction-oxidation pairs. You know what the possible reduction half cells could be to choose from; you know the possible oxidation half cells could be to choose from. If needed, choose to examine all possible combinations of redox pairs and determine the whole cell E's of each combination. The most positive value might correspond to the most favorable whole cell redox reaction. Just remind yourself that you need an oxidation to occur at the anode and you need a reduction to occur at the cathode. Fit the halfcell values accordingly.
 

FAQ: Predict the products of electrolysis

What is electrolysis and how does it work?

Electrolysis is a chemical reaction that uses electricity to break down a substance into its component parts. It involves passing an electric current through an electrolyte solution, causing the ions in the solution to move towards the electrodes. This movement of ions results in the separation of the substance into its constituent elements.

What factors influence the products of electrolysis?

The products of electrolysis depend on the type of electrolyte solution used, the type of electrodes, and the strength of the electric current. The chemical properties of the substance being electrolyzed also play a role in determining the products.

How do you predict the products of electrolysis?

Predicting the products of electrolysis involves understanding the chemical properties of the substance being electrolyzed and the reactions that occur at the electrodes. The products can be determined by looking at the chemical equations for the redox reactions that take place during electrolysis.

What is the difference between an anode and a cathode in electrolysis?

The anode is the positively charged electrode in electrolysis, while the cathode is the negatively charged electrode. At the anode, oxidation takes place, meaning electrons are lost. At the cathode, reduction occurs, meaning electrons are gained. The products of electrolysis are formed at the anode and cathode.

Can the products of electrolysis be controlled?

Yes, the products of electrolysis can be controlled by changing the conditions of the experiment, such as the strength of the electric current or the type of electrolyte solution used. However, certain factors, such as the chemical properties of the substance being electrolyzed, may limit the control over the products.

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