Question

1. Some compounds of sodium and calcium are given below. Match them.

A	B
(i) Washing soda (ii) Baking soda (iii) Gypsum (iv) Plaster of Paris	1. CaSO4.1/2H2O 2. Na2CO3 3.NaHCO3 4. CaSO4.2H2O

2. On passing CO₂ through lime water, milkiness appears. On further passing CO₂ milkiness disappears. What is the Chemistry behind it?

Answer 1

1. 

A	B
(i) Washing soda (ii) Baking soda (iii) Gypsum (iv) Plaster of Paris	1. Na2CO3 2. NaHCO3 3. CaSO4.2H2O 4. CaSO4.1/2H2O

2. When CO₂ is passed through lime water it turns milky due to the formation of insoluble calcium carbonate. 

Ca(OH)₂ + CO₂ → CaCO₃ + H₂O 

When CO₂ is passed through lime water for a long time, it becomes colourless due to the formation of water soluble calcium bicarbonate. 

CaCO₃ + H₂O + CO₂ → CaO(HCO₃)₂