Redox titrations

A sample of iron(II) sulfate crystals FeSO47H2O had been left out in the air and some of the Fe2ions had been converted to Fe3. A total of 4.2g of the impure crystals were dissolved in a total of 250cm3 of water and dilute sulfuric acid. Portions of 25cm3of this solution were titrated with a solution of potassium dichromate(VI). The concentration of dichromate(VI) ions in this solution was 0.1moldm3.The average titre was 23.50cm3. Use the following steps to find the percentage purity of the original crystals.
Original post by S1237
A sample of iron(II) sulfate crystals FeSO47H2O had been left out in the air and some of the Fe2ions had been converted to Fe3. A total of 4.2g of the impure crystals were dissolved in a total of 250cm3 of water and dilute sulfuric acid. Portions of 25cm3of this solution were titrated with a solution of potassium dichromate(VI). The concentration of dichromate(VI) ions in this solution was 0.1moldm3.The average titre was 23.50cm3. Use the following steps to find the percentage purity of the original crystals.

Hi there.

I can't do the Q for you but will give some tips.

First work out any moles from the given data and write a balanced equation and then find the moles of the other substance

Good luck