A sample of chalk $(CaCO_3)$ is contaminated with calcium sulphate $(CaSO_4)$ 1gm of the solid mixture is dissolved in 230ml of N/10 HCl; 40ml of N/10 NaOH is required to neutralize the excess of acid.Find the percentage of chalk in the mixture.

Question

$(a)\;95\%\qquad(b)\;92\%\qquad(c)\;93\%\qquad(d)\;91\%$