0.5 g of an oxalate was dissolved in water and the solution made to 100 mL. On titration 10 mL of this solution required 15 mL of `(N)/(20)KMnO_(4)`. Calculate the percentage of oxalate in the sample .

A sample of sodium carbonate contains sodium also. 1.5 g of the sample is dissolved in water and volume raised to 250 mL. 25 mL of this solution requires 20 mL of (N)/(10)H_(2)SO_(4) solution for neutralisation. Calculate the percentage of sodium carbonate in the sample.

In a sample of sodium carbonate some sodium sulphate is also mixed. 1.25 g of this sample is dissolved and the volume made up to 250 mL. 25 mL of this solution neutralises 20 mL of (N)/(10) sulphuric acid. Calculate the percentage of sodium carbonate in the sample.

10.875 g of a mixture of NaCl and Na_(2)CO_(3) was dissolved in water and the volume made up to 250 mL, 20 mL of this solution required 75.5 mL of (N)/(10) H_(2)SO_(4) . Find out the percentage composition of the mixture.

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) .