[CSG]

Hi, I would be very grateful if anyone could show me how to answer the following question:

The value of x in Fe(NH₄)₂(SO₄)₂. xH₂ O can be found by determining the amount in moles of sulfate in the compound.
A 0.982g sample was dissolved in water and excess BaCl₂ (aq) was added.
The precipitate of BaSO₄ was separated and dried and found to weigh 1.17g.

(a) Calculate the amount, in moles, of sulfate in the 0.982g sample of Fe(NH₄)₂(SO₄)₂. xH_2O

(according the the answers it's 0.00501 which I do not understand)

(b) Calculate the amount, in moles, of iron in the 0.982g sample of Fe(NH₄)₂(SO₄)₂. xH_2O

(apparently the answer is 0.00250 which is half of the previous answer - why?!)

Thanks in advance.

[Borek]

The precipitate of BaSO₄ was separated and dried and found to weigh 1.17g.

How many moles is that? How many moles of SO₄^2- per mole of BaSO₄?

apparently the answer is 0.00250 which is half of the previous answer - why?!

How many moles of SO₄^2- per mole of Fe(NH₄)₂SO₄?