Electrode potentials and electrochemical cells

Question 1

Why are salt bridges necessary?

Answer 1

To complete the circuit
Allows ions to flow, balancing the charge

Question 2

What symbol represents a salt bridge?

Answer 2

II

Question 3

What does I indicate?

Answer 3

Phase boundary

Question 4

How would a cell be represented in terms of oxidations and reductions?

Answer 4

(more -ve V) Reduction I Oxidation II Oxidation I Reduction (more +ve V)

Question 5

What happens at the left-hand electrode?

Answer 5

Oxidation reaction occurs
Most negative E* value

Question 6

What happens at the right-hand electrode?

Answer 6

Reduction reaction occurs
Most positive E* value

Question 7

What are the conditions for a standard hydrogen electrode (S.H.E.)?

Answer 7

Temp = 298K
Pressure = 100kPa
Concn = 1moldm-3

Question 8

What are the advantages of using a S.H.E.?

Answer 8

+ cheaper to use
+ provides a good reference point as 0.00V
+ platinum is expensive

Question 9

If E* is a more positive value, what does it mean in terms of oxidising / reducing power?

Answer 9

Better oxidising agent / easier to reduce

Question 10

How do you calculate the e.m.f. of a cell?

Answer 10

E* (cell) = E* (right) - E* (left)

Question 11

When do you use a platinum electrode?

Answer 11

When both the oxidised and reduced forms of the metal are in aqueous solution

Question 12

Why would you use a platinum electrode?

Answer 12

+ good conductor to complete the circuit
+ completely unreactive