electrolysis

Electrolysis

A process where electricity breaks up an ionic compound

What do you need to carry out electrolysis?

We need an electrolyte that can conduct electricity. Either a molten or dissolved ionic compound. In both cases ions can move freely so can move from one electrode to another

Electrode

Link between the liquid and electric circuit. Often made of graphite as it is unreactive and a good conductor of electricity

Electrolyte

A molten of dissolved ionic compound that is decomposed when a current passes

Anode

Negative ions moved towards it and lose an electron becoming an atom. They are oxidised

Cathode

Positive ions move towards it and gain electrons forming atoms. They are reduced

Which ions will react at the electrode?

The least stable ones

What is the overall equation of the electrolysis of water with sulfuric acid?

2H20 → 2H2 + 02

What is the overall equation of the electrolysis of concentrated sodium chloride solution?

2NaCl +2H20 → 2NaOH + H2 + Cl2

What is the use of sodium oxide?

To make soap

What is the use of hydrogen?

Fuel

What is the use of chlorine?

To kill bacteria in water

Chemical cells

They produce a voltage until one reactor is used up. With rechargeable batteries the reaction can be reversed by applying an electric current.

Advantages of fuel cells

Only product is pure water, doesn't produce CO2 so doesn't contribute to global warming, require no maintanence after set up,

Disadvantages of fuel cells

Not many hydrogen filing stations available as it is hard to store and transport. Hydrogen is flammable. Electricity is needed. Expensive.

Fuel cell

Works in the same way as a chemical cell but can have a continuous supply of reactants. In the cell a reverse of electrolysis occurs. The H2-02 cell provides electricity in space-craft and submarine. The hydrogen and oxygen react to form water and produce electricity. It can be obtained by the electrolysis of water and are constantly supplied so that the cell doesn't need recharging and does not run down

Uses of electrolysis

Electroplating:improve appearance, improve resistance to corrosion, makes it look more expensive, and purifying copper

Overall equation of electrolysis of water with sulfuric acid

2H20 → 2H2 + O2

Overall equation of electrolysis of concentrated sodium chloride

2NaCl + H20 → 2NaOH + H2 + Cl2