Electrode potentials

Question 1

What is conventional cell representation?

Answer 1

Zn|Zn2+||Cu2+|Cu

Question 2

What is the order of conventional cell representation?

Answer 2

Reduced, Oxidised, Oxidised, Reduced

Question 3

What are the rules for conventional cell representation?

Answer 3

• Species in the same state should not be separated by a line
• If there are no solid species, a platinum electrode should be seen in the cell representation
• Salt bridge is represented as ||
• More positive e.m.f is on the rhs

Question 4

What standard is used to measure all electrodes against?

Answer 4

Standard hydrogen electrode

Question 5

What are the standard conditions for SHE?

Answer 5

298K, 100kPa and 1 moldm⁻³ solution of ions

Question 6

How do you calculate emf?

Answer 6

Erhs - Elhs

Emore pos. - Emore neg.

Question 7

Commercial use electrode reactions for lithium cells

Answer 7

Positive electrode: Li⁺ + CoO₂ + e⁻ → Li⁺[CoO₂]⁻

Negative electrode: Li → Li⁺ + e⁻

Question 8

Non-rechargable cells

Answer 8

• Chemicals are used up over time and emf drops
• Cell can’t be recharged
• Hard to dispose of
• Cannot reverse change
• Long-lasting

Question 9

Rechargeable cells

Answer 9

• Lithium cells
• Money efficient
• Less waste but decline in performance

Question 10

Fuel cells

Answer 10

• Used to generate an electric current and do not need to be electrically recharged.
• Constant supply of chemicals
• Only waste product is water
• Efficient and high cost

Question 11

Fuel cell alkaline hydrogen/oxygen fuel cell equations

Answer 11

Anode: H₂ + 2OH⁻ → 2H₂O + 2e⁻
Cathode: O₂ + 2H₂O + 4e⁻ → 4OH⁻
Overall: 2H₂(g) + O₂(g) → 2H₂O(l)

Question 12

Advantages of fuel cells

Answer 12

• Water is the only product, no polluting/greenhouse gases

- More efficient than combustion engines

Question 13

Limitations of fuel cells

Answer 13

• Hydrogen is flammable
• Obtaining hydrogen as a fuel is difficult
• Limited lifetime
• Toxic cells used in their manifacture