A `0.56` g sample of limestones is dissolved in acid and the calcium is precipitated as calcium oxalate .The precipitate as calcium oxalate the prepcipate is filtered washed with water and dissolved in dil `H_(2)SO_(4)` The solution required `40ml` of `0.25NKmnO_(4)` solutions for titration .Calculate percentage of `0.25N` `KMnO_(4)` solution for titration .Calculate of `0.25N KMnO_(4)` solution for titration ,Calculate percentage of `CaO` in limestone sample.

Explanation

`CaCO_(3)+2H^(+)rarrCa^(2+)+CO_(2)+H_(2)O`
`Ca^(2+)+C_(2)O_(4)^(2-)rarrCaC_(2)O_(4)`
`CaC_(2)O_(4)+KMnO_(4)` in presence of `H_(2)SO_(4)` show the following redox changes:
`C_(2)^(3+)rarr2C^(4+)+2e`
`Mn^(7+)+5erarrMn^(2+)`
The above set of reaction shows:
Meq.of `CaO="Meq.of" CaC_(2)O_(4)="Meq.of" KMnO_(4)`
(Valence factor is two for `Ca` throughout the changes)
`(w_(CaO))/(56//2)xx1000=40xx0.25`
`therefore w_(CaO)=0.28`
`therefore % "of"CaO=(0.28)/(0.56)xx100=50%`