When a piece of limestone reacts with dilute HO, a gas X is produced. When gas X is passed through water then a white precipitate Y is formed. On passing excess of gas X, the white precipitate dissolve forming a soluble compound Z.

(a) What are X, Y and Z?


(b) Write equations for the reactions which take place:


(i) when limestone reacts with dilute HCl


(ii) when gas X reacts with lime water to form white precipitate Y


(iii) when excess of gas X dissolves white precipitate Y to form a soluble compound Z

(a) X is carbon dioxide;

Y is calcium carbonate;


Z is calcium hydrogen carbonate.


(b) (i) CaCO3(s) + 2HCl(aq) → CaCl2(aq) + CO2(g) + H2O(l)


(ii) Ca(OH)2 (aq) + CO2(g) → CaCO3(s) + H2O(l)


(iii) CaCO3 (s) + H2O(l) + CO2 (g) → Ca[HCO3]2 (aq).


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