Q1. Which of the following is incorrectly matched?
A Washing soda - Na2CO3
B Bleaching powder - CaO Correct
C Plaster of Paris - CaSO_{4}.\frac{1}{2}H_{2}O
D Baking Soda - NaHCO3
Explanation
Bleaching powder is not CaO; its usual formula is CaOCl2, so the given pairing with calcium oxide is incorrect. Washing soda is commonly represented as sodium carbonate, Na2CO3, though in hydrated form it is Na2CO3.10H2O. Plaster of Paris is calcium sulphate hemihydrate, CaSO4.1/2H2O, so that match is right. Baking soda is sodium hydrogen carbonate, NaHCO3, and is also correctly paired. The only clearly wrong match is bleaching powder with CaO.