Electrochemical Cells

Question 1

Why does the voltmeter need to have a high resistance?

Answer 1

To stop current from flowing in the circuit so you can measure the maximum potential difference

Question 2

Why is a metal wire not used as a salt bridge?

Answer 2

Because the metal would set up its own electrode system with the solutions

Question 3

Give a requirement of a salt bridge

Answer 3

It must be unreactive with the electrodes and electrode solutions so they do not form complexes with them

Question 4

Give the equation for the standard hydrogen electrode at equilibrium

Answer 4

H2 –>

Question 5

Give the cell diagram for a standard hydrogen electrode

Answer 5

Pt|H2|H+

Question 6

Give the equation occurring at the negative electrode of a hydrogen fuel cell

Answer 6

4OH- + 2H2 –> 4H2O + 4e-

Question 7

Give the equation for the reaction at the positive electrode of a hydrogen fuel cell

Answer 7

4e- + 2H2O + O2 –> 4OH-

Question 8

Give the overall reaction of a hydrogen fuel cell

Answer 8

2H2 + O2 –> 2H2O

Question 9

Give the equation of the reaction at the positive electrode of a lithium ion cell

Answer 9

Li+ + CoO2 + e- –> Li+[CoO2]-

Question 10

Give the equation for the reaction at the negative electrode of a lithium ion cell

Answer 10

Li+ + e- –> Li

Question 11

Give the overall reaction for a lithium ion cell

Answer 11

Li + CoO2 –> LiCoO2

Question 12

Give the cell notation for a lithium ion cell

Answer 12

Li | Li+ || Li+ , CoO2 | LiCoO2 | Pt

Question 13

Why are the reagents in a lithium ion cell absorbed onto powdered Graphite?

Answer 13

To use it as a support medium which allows the reaction to occur without a solvent. E.g. If water was used as a solvent, it would react with lithium

Question 14

Give 3 advantages of fuel cells over internal combustion engines

Answer 14

They produce less pollution and less CO2 as only water is released

The cells don’t need to be recharged like batteries as they only require a constant source of H2 and O2

Fuel cells convert more of their available energy to kinetic energy than ICEs which waste a lot of energy producing heat

Question 15

Give 3 disadvantages of fuel cells

Answer 15

They’re expensive (E.g. Producing hydrogen by electrolysis of water)

Storing and transporting explosive hydrogen is difficult

There may be the use of toxic chemicals or methods which produce pollutants in the production of hydrogen which mean the process isn’t carbon neutral