C6. Chemical Energetics

Question 1

Pros of nuclear fuels

Answer 1

1. Gives out a huge amount of energy

2. No CO2 or polluting gases formed

Question 2

Cons of nuclear fuels

Answer 2

1. Explosion in a nuclear power station could spread radioactive material over a huge area
2. Waste material produced is radioactive and needs to be stored safely for hundreds of years

Question 3

Pros of using hydrogen fuel cells

Answer 3

1. No CO2 produced (only water is formed)
2. No soot is formed, unlike fossil fuels
3. Highly efficient

Question 4

Cons of using hydrogen fuel cells

Answer 4

1. Storage of hydrogen is difficult
2. Takes more space to store hydrogen
3. High likelihood of hydrogen leaks
4. Lack of availability of hydrogen

Question 5

Hydrogen fuel cell: reaction at anode/negative pole

Answer 5

H2 –> 2H+ + 2e

Question 6

Hydrogen fuel cell: reaction at cathode/positive pole

Answer 6

O2 + 2H20 + 4e –> 4OH-

Question 7

6 examples of exothermic reactions

Answer 7

1. Neutralisation of acids by alkalis
2. Combustion of fuels
3. Respiration
4. Rusting of iron
5. Manufacture of ammonia in Haber process
6. Adding water to concentrated acids

Question 8

4 examples of endothermic reactions

Answer 8

1. Photosynthesis
2. Reaction between acid and sodium/potassium hydrogen carbonate
3. Thermal decomposition of metal nitrates
4. Thermal dissociation of metal carbonates and ammonium chloride