Question

1) Name the gas evolved, when marble is dropped in dilute hydrochloric acid taken in a test tube. Write a balanced chemical equation

Answer 1

Ans: Chemical formula of Marble is CaCO3. When this CaCO3 reacted with dilute HCl it produces Calciumchloride and Water along with liberation of Carbon dioxide gas.
 
CaCO3 + 2HCl → CaCl2 + H2O + CO2

Answer 2

when CaCO3 (marble) react with dilute HCl,it produces CaCl2 + H2O along with liberation of Carbon dioxide gas.

                           OR
we know that:

Metal   Carbonate + Acid => metal salt + CO2 + H2O

hence, CaCO3 + 2HCl     => CaCl2 + CO2 + H2O