Question

In the laboratory preparation of carbon dioxide by action of a dilute acid on a metallic carbonate give a reason for:

(i) use of a washer bottle containing cone. H₂SO₄ in the preparation 
(ii) Not collecting the prepared gas over water 
(iii) Not using dilute sulphuric acid as a reactant in the preparation.

Answer 1

1. Cone. H₂SO₄ used in washer bottle absorbs moisture from the gas.
2. C0₂ is soluble in water and hence is not collected over water.
3. Dil. sulphuric acid is not used as reactant. Since H₂SO₄ reacts with calcium carbonate forming- a coating of insoluble calcium sulphate [CaSO₄]. The reaction slowly comes to a stop.

\[\ce{CaCO3 + H2SO4(dil.)->\underset{\text{Insoluble}}{CaSO4} + H2O + CO2}\]