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 |
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|
| In anode H2 (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 |
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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