Q.Describe two important uses of each of the following :

(i) Caustic soda, NaOH — two important uses

1. Used in the manufacture of soaps and detergents, and of rayon (artificial silk), by treating cellulose with NaOH.
2. Used in the purification of bauxite ore (the Bayer process) during aluminium extraction, and generally in petroleum refining and the mercerising of cotton textiles.

(ii) Sodium carbonate, Na$_2$CO$_3$ (washing soda) — two important uses

1. Used in the manufacture of glass, and of other important sodium compounds such as borax.
2. Used domestically and industrially as a water softener, since it precipitates the Ca$^{2+}$/Mg$^{2+}$ ions responsible for water hardness, and it is also used in the paper, paints and textile industries.

(iii) Quicklime, CaO — two important uses

1. Used in large quantities in the manufacture of cement and, together with sand, in the manufacture of glass. …

Recall two well-established industrial applications for each compound: caustic soda in soap/rayon manufacture and ore purification; sodium carbonate in glass manufacture and as a wate …

• Confusing caustic soda's uses with sodium carbonate's uses (e.g. attributing 'glass manufacture' only to NaOH) — both are involved in glass-related industries but via different specific roles.
• Giving only one use per compound when the question explicitly asks for two. …