0.56g of limestone was treated with oxalic acid to give CaC2O4. The precipitate decolorised 45mL of 0.2NKMnO4 in acid solution. Calculate the % of CaO in limestone.
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Solution
45mL of 0.2NKMnO4=45mL of 0.2NCaC2O4 =45mL of 0.2NCaCO3 =45mL of 0.2NCaO Mass of CaO=N×E×V1000=0.2×28×451000=0.252g % of CaO in limestone =0.2520.56×100=45.