energy changes - fuel cells

Question 1

what happens in fuel cells?

Answer 1

hydrogen reacts with another reactant and water is the only waste product

Question 2

what is the half equation of a negative electrode?

Answer 2

2H2 > 4H+ + 4e-

Question 3

what is the half equation if a positive electrode?

Answer 3

O2 + 4H+ + 4e- > 2H2O

Question 4

what is the overall equation of a fuel cell?

Answer 4

2H2 + O2 > 2H2O

Question 5

what happens to hydrogen in a fuel cell?

Answer 5

it combines with oxygen meaning it is being oxidised

Question 6

what are the positives of hydrogen fuel cells and negatives of rechargeable batteries?

Answer 6

positives:
- produced electricity for as long as hydrogen is provided
- doesn’t get less efficient the longer they run
- it is a source of drinking water in space on aircraft

negatives:
- run out and need to be recharged
- can store less electricity the more charging cycles they go through and eventually will need to be replaced

Question 7

what are the negatives of hydrogen fuel cells and the positives of rechargeable batteries?

Answer 7

negatives:
- run on hydrogen which is an explosive gas and is very difficult to store safely
- produce relatively low potential difference or voltage so several needed to work together

positives:
- no dangerous fuels required. however some can catch on fire if manufactured incorrectly
- produced greater potential difference than hydrogen fuel cells and the