A 0.518 g sample of limestone is dissolved in HCl and then the calcium is precipitated as Ca_(2)C_(2)O_(4). After filtering and washing the precipitate, it requires 40 mL of 0.25 N KMnO_(4) solution acidified with H_(2)SO_(4) to titrate it as, MnO_(4)^(-) + H^(+) + C_(2)O_(4)^(2-) to CO_(2) + Mn^(2+) + 2H_(2)O The percentage of CaO in the sample is :

A 0.518 g sample of limestone is dissolved in HCl and then the calcium

1.	A 0.518 g sample of limestone is dissolved in HCl and then the calcium is precipitated as Ca_(2)C_(2)O_(4). After filtering and washing the precipitate, it requires 40 mL of 0.25 N KMnO_(4) solution acidified with H_(2)SO_(4) to titrate it as, MnO_(4)^(-) + H^(+) + C_(2)O_(4)^(2-) to CO_(2) + Mn^(2+) + 2H_(2)O The percentage of CaO in the sample is :
Answer» 0.54 `27.1%` 0.42 0.84 Solution :Number of milliequivalents of `CaC_(2)O_(4), KMnO_(4) " and" CAO` will be same. `40xx0.25=(W)/(56//2)xx1000` W=0.28 g (MASS of CaO) `% CaO=(0.28)/(0.518)xx100=54%`