Answer the following:
(i) What happens when a concentrated solution of sodium chloride is electrolysed? Write the equation of the reaction involved.
(ii) Why is the electrolysis of a concentrated solution of sodium chloride known as chlor-alkali process?
(iii) Name three products of the chlor-alkali process. State two uses of each product.
Answers
Answer:
The chloralkali process (also chlor-alkali and chlor alkali) is an industrial process for the electrolysis of sodium chloride solutions. It is the technology used to produce chlorine and sodium hydroxide (lye/caustic soda),[1] which are commodity chemicals required by industry. 35 million tons of chlorine were prepared by this process in 1987.[2] Industrial scale production began in 1892.
Usually the process is conducted on a brine (an aqueous solution of NaCl), in which case NaOH, hydrogen, and chlorine result. When using calcium chloride or potassium chloride, the products contain calcium or potassium instead of sodium. Related processes are known that use molten NaCl to give chlorine and sodium metal or condensed hydrogen chloride to give hydrogen and chlorine.
The process has a high energy consumption, for example over 4 billion kWh per year in West Germany in 1985.[3] Because the process gives equivalent amounts of chlorine and sodium hydroxide (two moles of sodium hydroxide per mole of chlorine), it is necessary to find a use for these products in the same proportion. For every mole of chlorine produced, one mole of hydrogen is produced. Much of this hydrogen is used to produce hydrochloric acid or ammonia, or is used in the hydrogenation of organic compounds.[4]