`0.56 g` of lime stone was treated with oxalic acid to give `CaC_(2)O_(4)`. The precipitate decolorized `45 ml` of `0.2N KMnO_(4)` in acid medium. Calculate `%` of `CaO` in lime stone.

Explanation

`"Limestone" overset("Oxalicacid")to CaC_(2)O_(4) overset(KMnO_(4))to "Decolorizes" CaCO_(3)`
During the reaction, following redox changes occur `C_(3)^(2+) to 2C^(4+)+2e ("oxidation of "C_(2)O_(4)^(2-))`
`5e+Mn^(7+) to Mn^(2+) ("reduction of "MnO_(4)^(-))`
so, meq. of `CaCO_(3)="meq. of "CaC_(2)O_(4)="meq. of "KMnO_(4)="meq. of CaO (Sinc CaO is present in "CaCO_(3))" and meq. of CaO =meq. of CaO=meq. of "KMnO_(4) (w)/(54//2) xx 1000=45 xx 0.2 =0.252 g`
`(E=M_(CaO//2))`
`W_(CaO)" in limestone "W_(CaO)=(0.252)/(0.56) xx 100=45%`