1. 6 gm of pyrolusite was treated with 50 ml of 0.5 M oxalic acid and some sulphuric acid. The oxalic acid left undecomposed was raised to 250 ml in a flask . 25 ml of this solution when treated with 0: 02 M KMnO_(4) required 32 ml of the Solution. Find the % of MnO_(2) in the sample and also the percentage of available oxyen .

1. 6 gm of pyrolusite was treated with 50 ml of 0.5 M oxalic acid and

1.	1. 6 gm of pyrolusite was treated with 50 ml of 0.5 M oxalic acid and some sulphuric acid. The oxalic acid left undecomposed was raised to 250 ml in a flask . 25 ml of this solution when treated with 0: 02 M KMnO_(4) required 32 ml of the Solution. Find the % of MnO_(2) in the sample and also the percentage of available oxyen .
Answer» Solution :Redox changes are `C_(2)O_(4)^(-2) to 2CO_(2) ` (n-factpr = 2) `MnO_(4)^(-) to Mn^(2+) ` (n-factor = 5) `MnO_(2) to Mn^(2+)` (n-factor = 2) Meq. Of `MnO_(2) ` = Meq. Of oxalic acid taken - Meq. Of oxalic acid left ` = 50 xx 0.5 xx 2 - 32 xx 0.02 xx 5 xx 10 ` (in250ml) = 18 `W_(MnO_(2))/M_(MnO_(2)) xx 2 xx 1000 = 18 rArrW_(MnO_(2))/87 xx 2 xx 1000 = 18 `, `:. W_(MnO_(2)) = 0.7821 ` gm ` :.% " of " MnO_(2) = (0.7821)/ (1.6) xx 100 = 48.88 %` Meq. of `MnO_(2)` = Meq. of `O_(2) ` `W_(O_(2)) /16 xx 2 xx 1000 = 18, :. w_(o_(2)) = 0.144` g % of AVAILABLE `O_(2) = (0.144)/(1.6) xx 100 = 9 `