1.6 g of pyrolusite ore was treted with 50 " mL of " 1.0 N 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 titrated with 0.1 N `KMnO_4` required 32 " mL of " this solution. Find out the percentage of pure `MnO_2` and also the percentage of available oxygen from `MnO_2`.

0.6 g of a sample of pyrolusite was boiled with 200 " mL of " (N)/(10) oxalic acid and excess of dilute sulphuric acid. The liquid was filtered and the residue washed. The filtrate and washing were mixed and made up to 500 mL in a measuring flask. 100 " mL of " this solution required 50 " mL of " (N)/(30)KMnO_4 solution. Calculate the percentage of MnO_2 in the sample (Mn=55) .

0.6 g of a sample of pyrolusite was boiled with 200 " mL of " (N)/(10) oxalic acid and excess of dilute sulphuric acid. The liquid was filtered and the residue washed. The filtrate and washing were mixed and made up to 500 mL in a measuring flask. 100 " mL of " this solution required 50 " mL of " (N)/(30)KMnO_4 solution. Calculate the percentage of MnO_2 in the sample (Mn=55) .

0.592 g of calcium oxalate was dissolved in dilute acid and the solution was made up to 250 mL. 25 mL of this solution required 8.375 mL of 0.1 N KMnO_4 solution for complete oxidation. Calculate the percentage of calcium oxalate in calcium oxalate sample.