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What is brine?
How can we make use of the products from the electrolysis of Brine?
Brine is a concentrated or saturated solution of sodium chloride in water.
The process of electrolysis uses electrical energy to produce a chemical reaction in the
sodium chloride solution which results in the formation of sodium hydroxide, chlorine and
NaCl + H2O =electrolysis=> NaOH + H2 + Cl2
The manufacture of sodium hydroxide or caustic soda is an important industrial process.
Because Sodium hydroxide is caustic in nature it must be handled with care. It is used in
industry in the manufacture of soap by saponification. It is also used to make pulp and in the
production of paper.
The electrochemistry involved in the reaction involves a reduction oxidation reaction, which
is sometimes called a redox reaction.
Electrolysis of salt solution, NaCl
In a solution of brine there are three chemical species: The sodium ion, Na , the chloride ion, Cl and
water, H2O. The easiest chemical species to oxidise is the chloride ion. The easiest chemical species
to reduce is the water.
The anode is the electrode where oxidation or the loss of electrons takes place. In an electolytic cell
the anode is positive in charge. The chloride ion is oxidised to chlorine gas.
Cl =oxidation=> ½Cl2 + e
H2O + e =reduction=> ½H2 + OH
In water the sodium ion is not reduced as it is much easier to reduce water. The sodium ion
becomes a spectator ion and is not involved in the reaction.
The overall chemical equation for the electrolysis of brine is
NaCl + H2O =electrolysis=> H2 + Cl2 + NaOH
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In industry the hydrogen gas must be separated from the chlorine gas or they will explode when
exposed to UV light producing hydrogen chloride. H2 + Cl2 =UV=> 2HCl
1. When we electrolyse brine we get three products chlorine gas, hydrogen gas and
sodium hydroxide solution.
2. Chlorine is used to kill microbes in drinking water and swimming pools, and to make
hydrochloric acid, disinfectants, bleach and plastics.
3. Hydrogen is used to make margarine and hydrochloric acid.
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A half-equation shows you what happens at one of the electrodes during electrolysis.
Electrons are shown as e-. A half-equation is balanced by adding, or taking away, a number
of electrons equal to the total number of charges on the ions in the equation.
At the negative electrode
Positive ions gain electrons at the negative electrode, so are reduced.…read more