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stuck AQA Nelson thornes book pg 225-266 (hard I think lol)

This question is regarding the e.g. on page 225 which starts with heading 'Worked example'

Me and my friend understand what has gone on here but we were then thinking

okay what if we actually had [(Fe)2(SO4)5)] (we don't think this is a real compound but we are just saying if we had something like this lol) how we would apply what we have been shown on those pages to this compound.

Anyway for this made up compound the working is pretty much the same up until the 6th line on page 226 where we find that

1 tablet contains 1.315 x 10-3 mol of Fe2+
okay now they then go on to say that

Since 1 mol iron (ii) sulfate contains 1 mol of Fe2+, each tablet contains
1.315 x 10-3 mol FeSO4. They then find the relative formula mass i.e. 151.9, multiply the moles by the formula mass i.e. (1.315 x 10-3) x 151.9 to obtain the mass

right so in applying this to our made up example [(Fe)2(SO4)5)] is what we are struggling with. Following their format :

"1 tablet contains 1.315 x 10-3 mol of Fe5+ "
so followinf their format:
since 1 mol of iron sulfate contains TWO moles of Fe 5+, each tablet contains (1.315 x 10-3) x 2 moles of [(Fe)2(SO4)5)].
(1.315 x 10-3) x 2 = 2.63 x 10 -3

so we have 2.63 x 10 -3 moles of [(Fe)2(SO4)5)]. We would then work out the relative formula mass for [(Fe)2(SO4)5)] and multiply this by our number of moles.

However we don't think this is right. We have been trying to figure it out for ages but we are both really confused now :colondollar:

(If you don't have the book I can attach pictures but it is easier if you have the book as I think it will be less confusing for u to understand what we are struggling with)

(edited 10 years ago)

Reply 1

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