# Determination of the formula of hydrated iron sulphate

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Introduction

Determination of the formula of hydrated iron sulphate Analysis Method 1 Results Mass of iron sulphate before heating 1.372 Mass of iron sulphate after heating the 1st time 0.698 Mass of iron sulphate after heating the 2nd time 0.718 Mass of iron sulphate after heating the 3rd time 0.720 Mass of iron sulphate after heating the 2nd time 0.720 Final mass of iron sulphate after heating 0.720 The mass of FeSO4. xH2O I weighed out to begin was 1.372g. After heating the mass was 0.720g. Having heated the FeSO4. xH2O all of the water has evaporated out so the mass that I am left with is the mass of FeSO4 which was 0.72 g. The mass of the H2O can then be calculated by subtracting the mass of FeSO4 from the mass of FeSO4. xH2O. Therefore; Mass of H2O = Mass of FeSO4. xH2O - Mass of FeSO4 Mass of H2O = 1.372 - 0.72 Mass of H2O = 0.652g So I now know both the mass of H2O and the mass of FeSO4 . ...read more.

Middle

titration was taken from the 2nd and 3rd titrations and not the 1st as the 1st was only a test to see where roughly the end point was. Analysis To calculate the formula of the FeSO4.xH2O I need to first calculate the moles of Fe2+. To do this I need to first calculate the moles of MnO4-. I can do this using the following equation. Moles of MnO4- = volume x concentration 1000 I know the volume of the MnO4- as this is what I had to find out with the titration. The concentration of this solution was given as 0.01 mol dm-3. The equation is therefore: Moles of MnO4- = 22.25 x 0.01 1000 Moles of MnO4- =0.0002225 This is the amount of moles of MnO4- However I need to find out the moles of Fe2+. I can now do this using the ratio of Fe2+ to MnO4- . ...read more.

Conclusion

xH2O. Mass of H2O = mass of FeSO4. xH2O - mass of FeSO4 Mass of H2O = 3.00 - 1.72 Mass of H2O = 1.28g Now that I have the mass of the H2O I can calculate the moles of H2O using the equation: Moles = Mass Mr Moles = 1.28 ((1x2) +16) Moles = 0.0713 correct to 3 significant figures Number of moles of H2O = 0.0713 I also know the moles of FeSO4 from previous equations earlier. Number of moles of FeSO4 = 0.0113 To calculate the formula of FeSO4. xH2O the smallest number of the two values for the moles of FeSO4 and H2O needs to be made to 1 and the ratio then calculated. To do this both numbers are divided by the smallest number. FeSO4 H2O 0.0113 0.0713 0.0113 0.0113 = 1 = 6.31 The ratio of FeSO4 to H2O must be in whole numbers as reacting ratios need to be integers. From this experiment I can therefore say the ratio is 1:6 so in FeSO4. xH2O x = 6 and the formula is; FeSO4. 6H2O. ...read more.

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