Chemical cells and fuel cells (chemistry only)

5.2.1 Cells and batteries

  • Cells – chemical react → produce electricity
  • Voltage produced depend on type of electrode & electrolyte
  • Simple cell – connect 2 different metals in contact with electrolyte
  • Batteries – 2+ cells connected in series to provide greater voltage
  • Non-rechargeable – chemical reaction stops coz 1 reactant used up eg alkaline batteries
  • Rechargeable – reversible reaction → connected to external electrical current

5.2.2 Fuel cells

Bigger the difference of reactivity between metal electrode & copper, higher the voltage

Hydrogen fuel cells

In alkaline condition In acidic condition
In anode H(g) + 2OH– (aq) → 2H2O (l) + 2e

In cathode O2 (g) + 2H2O (l) + 4e → 4OH

Overall 2H2 (g) + O2 (g) → 2H2O (l)

In anode H2 (g) → 2H+ (aq) + 2e

In cathode O2 (g) + 4H+ (aq) + 4e → 2H2O (l)

Overall 2H2 (g) + O2 (g) → 2H2O (l)


Advantages Disadvantages
  • X electrically recharged
  • X pollution coz only water is produced
  • Range of sizes for different uses
  • Highly flammable
  • If H2 – not come from renewable source
  • Hard to store coz explosive

What type of energy is released by hydrogen fuel cells? (1)

  • Electrical

Batteries consist of electrochemical cells. Describe how a 9.0V battery can be made from cells of voltage 1.5V (2)

  • Use 6 cells of 1.5V each
  • Connect them in series to create a batter of 9V

Non-rechargeable cells eventually stop producing electricity. Explain why and name a typical cell that is non-rechargeable. (4)

  • One of the reactants is used up which stops the chemical reactions
  • There’s no flow of electrons so cell stops producing electricity
  • Alkaline batteries are typical non-rechargeable cells

Give 2 reasons why using hydrogen fuel cells is seen as a clean source of energy (2)

  • Produce water which is non-polluting

Rechargeable cells are cells that can be recharged. Explain how this process occurs (4)

  • The chemical reactions are reversed when an external electrical current is supplied

Give 3 factors that affect the voltage produced by cell (3)

  • Type of electrode
  • Concentration of electrolyte
  • Temp
  • Electrolyte