a. Describe one method of manufacture of castic soda.
b. What happens when caustic soda reacts with
i. Ai metal , ii. `CO_(2)` , iii. `SiO_(2)`
c. Describe four industrial uses of caustic soda.

Explanation

a.
b. Reaction of sodium hydroxide with:
i. Aluminium metal:
`2AI+2NaOH+2H_(2)O rarr underset("Sodium meta aluminate")(2NaAIO_(2)+3H_(2)uarr)`
ii. Carbon dioxide: It dissolves in it and `Na_(2)CO_(3)` is produced.
`CO_(2)+2NaOH rarr Na_(2)CO_(3)+H_(2)O`
iii. `SiO_(2)`: Weakli acidic in nature and when it is heated with concentrated solution of sodium hydroxide, a base, `SiO_(2)` dissolves in sodium hydroxide and forms sodium silicate.
`SiO_(2)+2NaOH rarr underset(("Sodium silicate"))(Na_(2)SiO_(3))+H_(2)O`
c. Industrial uses of caustic soda or NaOH:
i. Sodium hydroxide is used in the manufacture of soap, paper, artificial silk and a number of chemicals.
ii. It is used in petroleum refining.
iii. It is used in the purifuication of bauxite (ore of aluminium).
iv. It is used in the textile industry for mercerising cotton fabrics.