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AQA GCSE SCIENCE - C2 6 - Electrolysis
a) Electrolysis is the decomposition of a substance to give simpler substances.
The substance being electrolysed has to be an ionic compound.
b) The substance being decomposed is called the electrolyte.
c) In electrolysis the electric current enters and leaves the electrolyte by
conducting rods called electrodes. The positive electrode is called the anode
and the negative electrode is called the cathode.
d) For electrolysis to occur the electrolyte must be in liquid form so that the
ions are free to move.
e) In electrolysis the negative ions move towards the anode. When they get
there they lose electrons to form neutral atoms. The positive ions move
towards the cathode. When they get there they gain electrons to form neutral
Electrolysis is the process by which ionic substances are broken down into
simpler substances using electricity. During electrolysis, metals and gases may
form at the electrodes.
To understand electrolysis, you need to know what an ionic substance is.
Ionic substances form when a metal reacts with a non-metal. They contain charged
particles called ions. For example, sodium chloride forms when sodium reacts with
chlorine. It contains positively charged sodium ions and negatively charged chloride
ions. Ionic substances can be broken down by electricity.
Electrolysis is the process by which ionic substances are decomposed (broken down)
into simpler substances when an electric current is passed through them.
For electrolysis to work, the ions must be free to move. Ions are free to move when an
ionic substance is dissolved in water or molten (melted). For example, if electricity is
passed through copper chloride solution, the copper chloride is broken down to form
copper metal and chlorine gas.
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AQA GCSE SCIENCE - C2 6 - Electrolysis
Here is what happens during electrolysis:
Positively charged ions move to the negative electrode during electrolysis.
They receive electrons and are reduced.
Negatively charged ions move to the positive electrode during electrolysis.
They lose electrons and are oxidised.
Predicting the products of electrolysis
Ionic substances in solution break down into elements during electrolysis. Different
elements are released depending on the particular ionic substance.
At the negative electrode
At the negative electrode, positively charged ions gain electrons.…read more

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AQA GCSE SCIENCE - C2 6 - Electrolysis
The reactivity series of metal - carbon and hydrogen are not metals, but they are
shown for comparison
So the electrolysis of copper chloride solution produces copper at the negative
electrode. But the electrolysis of sodium chloride solution produces hydrogen.
At the positive electrode
At the positive electrode, negatively charged ions lose electrons. This is oxidation, and
you say that the ions have been oxidised.…read more

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AQA GCSE SCIENCE - C2 6 - Electrolysis
copper chloride, CuCl2 copper chlorine
copper sulfate, CuSO4 copper oxygen
sodium chloride, NaCl hydrogen chlorine
hydrochloric acid, HCl hydrogen chlorine
sulfuric acid, H2SO4 hydrogen oxygen
Purification of copper
Copper is a good conductor of electricity, and is used extensively to make electrical
wiring and components. The extraction of copper from copper ore is done by
reduction with carbon. However, the copper produced is not pure enough for use as a
conductor, so it is purified using electrolysis.…read more

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AQA GCSE SCIENCE - C2 6 - Electrolysis
Electrolysis of sodium chloride solution
These three products - hydrogen, chlorine and sodium hydroxide - have important
uses in the chemical industry:
making ammonia
making margarine
killing bacteria in drinking water
killing bacteria in swimming pools
making bleach
making disinfectants
making hydrochloric acid
making PVC
making CFC's - limited production
Sodium hydroxide
making soap
making paper
making ceramics
A half-equation shows you what happens at one of the electrodes during electrolysis.…read more

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AQA GCSE SCIENCE - C2 6 - Electrolysis
At the negative electrode
Positive ions gain electrons at the negative electrode, so are reduced.
In aluminium extraction: Al3+ + 3e- Al
In copper purification: Cu2+ + 2e- Cu
Electrolysis of sodium chloride solution: 2H+ + 2e- H2
At the positive electrode
Negative ions or neutral atoms lose electrons at the positive electrode and are
oxidised.…read more


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