Chemical Cells & Fuel Cells

Question 1

Suggest why batteries should not be put in household waste.

Answer 1

• (metal / alkaline waste) can be toxic / harmful / corrosive
• (metal / alkaline waste) could cause pollution in landfill sites
• recycling would save resources

Question 2

The voltage produced by the cell in Figure 2 depends on the type of
electrodes and the type of electrolyte.
Suggest one other factor that could affect the voltage produced.

Answer 2

• temperature (of electrolyte / solution)
• concentration (of electrolyte / solution)

Question 3

Complete the word equation to show the reaction that produces water in a
hydrogen fuel cell.

Answer 3

hydrogen + oxygen -> water

Question 4

The reaction between hydrogen and oxygen is used in a hydrogen fuel cell.
What is the reason for using this reaction in a fuel cell?

Answer 4

to produce a potential difference

Question 5

The metals used were:
* copper
* iron
* magnesium.
Which two metal electrodes would produce the greatest voltage when
used in the chemical cell?
Give one reason for your answer

Answer 5

magnesium and copper

(the metals) have the largest difference in reactivity

Question 6

Give two advantages of using hydrogen fuel cells instead of using
rechargeable cells to power cars.

Answer 6

• no toxic chemicals to dispose of at the end of the cell’s life
• take less time to refuel (than to recharge rechargeable cells)
• travel further before refuelling (than before recharging
  rechargeable cells)

Question 7

Give two limitations of this simple particle model for hydrogen gas

Answer 7

• particles are shown as spheres
• particles are shown as solid
• does not show the (weak) forces (between particles)
• does not show the movement / speed (of particles)
• is only two-dimensional

Question 8

The hydrogen gas needed to power a car for 400 km would occupy a large
volume.
Suggest one way that this volume can be reduced.

Answer 8

• under (higher) pressure
• cool
• absorb / adsorb in a solid

Question 9

Copper is used as electrode X in Figure 1.
Predict the voltage of this cell.
Give one reason for your answer

Answer 9

0 (volts)

two different metals are needed to produce a voltage

Question 10

Describe how to make a 12 V battery using 1.5 V cells.

Answer 10

connect 8 cells (in series)

Question 11

Suggest one advantage and one disadvantage of using a hydrogen fuel
cell compared with a rechargeable cell.

Answer 11

• faster to refuel (than recharging)
• can travel further (before refuelling)
  allow lasts longer
• hydrogen can be renewable
  allow hydrogen is renewable
• produces a constant voltage
• no toxic chemicals released after disposal
• hydrogen is made from fossil fuels
• hydrogen is made from non-re

Question 12

Some diesel trains are being converted to run on hydrogen fuel cells.
A newspaper article referred to the converted trains as the new ‘steam
trains’.
Suggest why.

Answer 12

hydrogen is oxidised to produce water.
water is produced / released as gas / vapour / steam

Question 13

Complete the balanced equation for the overall reaction in a hydrogen fuel
cell.

Answer 13

2H2 + O2 ⟶ 2H2O

Question 14

Why do non-rechargeable cells stop producing electricity?

Answer 14

reaction stops

(because) one of the reactants is used up

Question 15

Give two reasons why using a hydrogen fuel cell is seen as non-polluting.

Answer 15

• produces water
• water is not harmful / polluting
• does not produce carbon dioxide
• does not produce other named pollutant

Question 16

Give two factors that affect the voltage produced by a cell.

Answer 16

• type of electrode
• electrolyte
• concentration of electrolyte
• temperature

Question 17

Balance the half-equation for the reaction occurring at an electrode in one
type of hydrogen fuel cell.
H2 + OH− ⟶ H2O + e−

Answer 17

H2 + 2OH− → 2H2O + 2 e−

Question 18

Why is the fuel cell described as an alkaline fuel cell?

Answer 18

contains OH−
ions

Question 19

Write the two half equations for the reactions that occur at the electrodes
in a hydrogen fuel cell.

Answer 19

H2 → 2H+ + 2e−

O2 + 4H+ + 4e− → 2H2O