2018 Chemistry Mistakes

Question 1

How do fuel cells work

Answer 1

• the fuel is oxidised at the anode (which is negative) and sets up a potential difference within the cell
• the electrodes are often POROUS carbon with a CATALYST
• at the anode the hydrogen looses electrons to become oxidised
• the H+ ions in the electrode move to cathode. At the cathode the oxygen gains electrons from cathode REDUCTION
• the electrons flow through a external circuit from anode to cathode x electric current

Question 2

Give equations involved with fuel cells

Answer 2

H2 —> 2e- + 2H+ ( anode)
O2 + 4H+ 4e- —> 2H20
2h2 + o2 —> 2H20

Question 3

Differences of hydrogen fuel and chemical cells

Answer 3

Fuel cells are better : hydrogen can be renewable if made by electrolysis using renewable energy
• lithium-ion batteries can catch fire
• produces only water
or
no pollutants produced
• lithium-ion batteries may release
toxic chemicals on disposal
• lithium-ion batteries (eventually
cannot be recharged so) have a finite life

However chemical cells are better as:

hydrogen is often made from fossil fuels so is not renewable
• charging points are more widely available than hydrogen filling stations
• hydrogen takes up a lot of space or
is difficult to store
• hydrogen can be highly flammable
/ explosive
• no emissions produced
• (catalyst in the hydrogen fuel-cell
eventually becomes poisoned so) have a finite life