3.1.11 Electrode Potentials

Question 1

How is an electrochemical cell set up? (3)

Answer 1

Two metal electrodes are each dipped in a solution of their positive ions
The electrodes are connected by a wire to a voltmeter
A salt bridge between the two beakers allows ions to flow between the half-cells

Question 2

How do electrons flow in an electrochemical cell?

Answer 2

Through the wires from the most reactive metal to the least

Question 3

Why is platinum used as an electrode? (2)

Answer 3

Inert

Conducts electricity

Question 4

What is the role of the electrode?

Answer 4

Provides a surface for oxidation/reduction to take place on

Question 5

What does the electrode potential of a metal indicate?

Answer 5

How easily oxidised it is (more negative means more easily oxidised)

Question 6

How are electrochemical cells conventionally represented? (6)

Answer 6

Reduced forms on the edges
Oxidised forms in the middle
Double vertical line shows salt bridge
Different phases separated by single line
Substances in the same phase separated by commas
More negative electrode potential on left

Question 7

How is cell potential calculated? (2)

Answer 7

E(right) - E(left)

E(reduced) - E(oxidised)

Question 8

Why are standard conditions used to measure electrode potentials?

Answer 8

Changes in conditions causes the equilibrium position to change

Question 9

What is the standard hydrogen electrode? (3)

Answer 9

The half-cell used to measure other electrode potentials against
Hydrogen gas (100kPa) bubbled through solution of H+ ions (1M)
Platinum electrode

Question 10

How is the direction of a reaction predicted from electrode potentials? (2)

Answer 10

The reaction with a more negative electrode potential will be oxidation and the more positive electrode potential will be reduction
The reaction will only occur in the direction that gives a positive EMF