Chalk is impure calcium carbonate. The amount of calcium carbonate present can be determined by hydrochloric acid to a sample of chalk and measuring the volume of carbon dioxide produced CaCo3(aq) + 2HCl -> CaCl2(aq) + Co2(g) + H2O(g) Excess hydrochloric acid was added to 0.5g chalk and 100cm3 of carbon dioxide gas was given produced at r. t.p calculate the percentage purity of calcium carbonate in sample of chalk Read more at Answer. Ya. Guru – https://answer. ya. guru/questions/2218120-chalk-is-imp ure-calcium-carbonate-the-amount-of -calcium. html