Iron II Sulphate In Iron Tablets

SIXTH FORM GOVERNMENT SCHOOL
LAB EXPERIMENT
TITLE: DETERMINATION OF THE MASS OF IRON (II) SULPHATE IN BRAND ‘X’ OF IRON TABLETS
TEACHER’S REMARKS:
Iron is a mineral that is a constituent in haemoglobin. Iron tablets usually contain iron in a cheap soluble form such as iron (II) sulphate. You are provided with brand ‘X’ of iron tablets which contains iron (II) sulphate along with other compounds. You are to prepare a solution of this tablet which has been grounded for you. You are also required to titrate this solution with a standard solution of potassium manganate solution. This type of titration is an example of a redox titration.
PROCEDURE:
(A) Preparation of Solution ‘X’
1. Weigh 6g of brand ‘X’ of iron tablets
2. Dissolve in 100cm3 of 1.0 moldm-3 H2SO4(aq) in a conical flask. When necessary, gently warm the flask over the Bunsen burner. DO NOT BOIL THE MIXTURE.
3. Filter any solid.
4. Transfer any filtrate to a 250cm3 volumetric flask. Fill the solution up to the mark with distilled water. Label as solution X.

(B) Titration of Solution X with Potassium Manganate (VII) Solution
1. Pipette 25cm3 of solution X into a conical flask. Add 25cm3 of 1.0 moldm-3 sulphuric acid using a measuring cylinder.
2. Rinse and fill the burette with 0.01moldm-3 potassium manganite (VII) solution.
3. Titrate the solutions until the first pale pink colour is observed.
4. Repeat the titration 2 more times.
RESULTS:

1
2
3
Initial burette reading/ cm3

Final burette reading/ cm3

Volume of KMnO4 used/ cm3

CALCULATIONS:
1. Determine the volume of potassium manganate used.
2. Calculate how many moles of potassium manganate are in the volume stated above.
3. How many moles of Fe2+ have reacted with potassium manganate above?
4. How many moles of iron(II) sulphate are in the 250cm3 of solution?
5. What is the mass of iron (II) sulphate in brand X of iron tablets?
6. What is the percent by mass of iron (II) sulphate in brand X of iron tablets?
QUESTIONS TO ANSWER IN YOUR DISCUSSION:
1. Why was it necessary to dissolve the table in sulphuric acid?
2. Why should the mixture not be boiled? (The answer for this can be stated with your precautions).
3. The mass of the iron tablets according to the label is 50% by mass. Did this coincide with your answer? If it did not, explain any possible sources of error/ limitations which may have caused your answer to be different.