(a) NaOH +....... Na2S04 + H20
(b) Ca(OH)2 +.... CaC03 + H20
Sodium hydroxide reacts with Sulphuric acid to give Sodium sulphate and water.
(b) Ca(OH)2 + C02 CaC03 + H20
Calcium hydroxide reacts with carbon dioxide to give Calcium carbonate and water.