CHAPTER 5. THE CHEMICAL INDUSTRY 5.3
More practice video solutions or help at http://www.everythingscience.co.za(1.) 01rk (2.) 024f (3.) 024g (4.) 024h (5.) 024i (6.) 024j5.3 The Chloralkali Industry
The chlorine-alkali (chloralkali) industry is animportant part of the chemical indus-
try, and produces chlorine and sodium hydroxide through the electrolysisof table salt
(NaCl). The main raw material is brine which is a saturated solution of sodium chloride
(NaCl) that is obtained from natural salt deposits.
The products of this industry have a number ofimportant uses. Chlorine is used to
purify water, and is used as a disinfectant. It isalso used in the manufacture of many
every-day items such ashypochlorous acid, which is used to kill bacteria in drinking
water. Chlorine is also used in paper production, antiseptics, food, insecticides, paints,
petroleum products, plastics (such as polyvinylchloride or PVC), medicines, textiles,
solvents, and many other consumer products. Many chemical products such as chloro-
form and carbon tetrachloride also contain chlorine.
Electrolytic cells are used to transform reactantsinto products by using electric current.
They are made up of an electrolyte and two electrodes, the cathode and the anode.
An electrolytic cell is activated by applying an external electrical current. This creates
an electrical potential across the cathode and anode, and forces a chemical reaction to
take place in the electrolyte. Cations flow towards the cathode and are reduced. Anions
flow to the anode and are oxidised. Two new products are formed, oneproduct at the
cathode and one at theanode.
Sodium hydroxide (also known as ’causticsoda’) has a number of uses, which include
making soap and other cleaning agents, purifyingbauxite (the ore of aluminium), mak-
ing paper and making rayon (artificial silk).
The Industrial Production of Chlo-
rine and Sodium HydroxideESCCJ
Chlorine and sodium hydroxide can be produced through a number ofdifferent reac-
tions. However, one ofthe problems is that when chlorine and sodiumhydroxide are
produced together, the chlorine combines with the sodium hydroxide toform chlorate
(ClO−) and chloride (Cl−) ions. This produces sodium chlorate, NaClO,a component