Question

A sodium salt is placed in a dry test tube. To this salt is added 5 ml of hydrochloric acid. Then a lot of effervescence takes place with the liberationof a colourless gas. The gas on passing through a colourless solution turns it milky. Answer the following questions.(a) Which gas is produced during the chemical reaction?(b) What is the colourless solution and why does it turn milky?(c) What happens when excess of this gas is passed through the colourless solution?Write balanced chemical equations for all the reactions involved.

Answer 1

The answers of the following questions are:

(a) Carbon dioxide gas is produced in the chemical reaction as it produces effervescence.

- The salt may be sodium carbonate.

Na2CO3 + 2 HCl → 2 NaCl + CO2 + H2O

(b) The colourless solution is lime water and it turns milky on passing CO2 due to the formation of Calcium Carbonate.

Ca(OH)2 + CO2 → CaCO3 + H2O

(c) When excess of CO2 is passed through lime water, it again turns colourless due to formation of Calcium hydrogen carbonate which is colourless.

CaCO3 + H2O + CO2 → Ca(HCO3)2