SSC JE Civil Engineering 29-Oct-2020 Shift 1 Paper

Explanation:
The amount of Calcium Carbonate in limestone is determined by performing the acid test. The acid used is dilute Hydrochloric acid. The reaction involved is:
${\mathrm{CaCO}}_3+2\mathrm{HCl}$ $\to {\mathrm{CaCl}}_2+{\mathrm{H}}_2\mathrm{O}+{\mathrm{CO}}_2$
The method used for measuring ${\mathrm{CaCO}}_3$ comprises the following steps
1. Dissolving limestone in hydrochloric acid.
2. Adding KOH solution and Calcium Carboxylate indicator into said solution.
3. Titrating the solution until its color turns to blue from red using EDTA standard solution and then working out the ${\mathrm{CaCO}}_3$ content on the basis of the titer of EDTA.