Chapter 23: Electrode Potentials Flashcards
1
Q
What is a half-cell?
A
- A half cell contains the species present in a half-equation
2
Q
What are the 3 types of half-cells, and what does each contain?
A
- Metal/ metal ion: a metal is dipped into a solution of its metal ions
- Ion/ ion: metal ions in different oxidation states are in the solution, and there is a platinum electrode
- Non-metal/ ion: glass tube connected to a gas supply of the non-metal, its ions are in solution, and there is a platinum electrode
3
Q
How are the species in half-cells represented? Show using an example.
A
- Cu2+ (aq)|Cu (s)
4
Q
What do cells do, and how are they made?
A
- They turn chemical energy into electrical energy
- By connecting 2 half-cells
5
Q
How do cells work?
A
- The electrode that is more likely to release electrons (the stronger reducing agent) is the negative electrode
- Oxidation takes place at the negative electrode
- It transfers electrons to the positive electrode
- Reduction takes place at the positive electrode
6
Q
What limitation is there in a set up with just 2 half-cells? What is done to prevent this?
A
- Eventually there would be a build up of positive ions in the negative electrode’s solution and a build up of negative ions in the positive electrode’s solution
- A salt bridge is added to slowly release anions and cations to stop too much charge building up in the solutions as they would react with the ions
7
Q
How would you make a salt bridge?
A
- Soak filter paper in a solution of concentrated potassium nitrate (or another salt that would not react with either solution)
8
Q
How are half-equations written for the reactions taking place in a cell?
A
- They are written as a reversible reaction with the forward reaction showing reduction
9
Q
How can the tendency of a metal to lose and gain electrons be measured?
A
- Using standard electrode potential, E^⦵
10
Q
How are standard electrode potentials determined?
A
- Hydrogen half-cells are taken as having a standard electrode potential of 0V
- A hydrogen half-cell is then connected to another half-cell (so that you can find its standard electrode potential)
- The electrode potential under standard conditions is then measured using a voltmeter
11
Q
What are standard conditions when measuring electrode potentials?
A
- 298K
- 100kPa
- 1 moldm^-3
12
Q
What is the equation for standard cell potential?
A
-E⦵cell = E⦵(positive electrode) - E⦵(negative electrode)
13
Q
What do negative standard electrode potentials show?
A
- That the metal is a strong reducing agent
