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Chemistry Forums for Students => High School Chemistry Forum => Topic started by: Kommandante on December 09, 2013, 04:44:38 PM

Title: How to calculate the mole of an element in a compound?
Post by: Kommandante on December 09, 2013, 04:44:38 PM

Hi there,

I have been given the formula for Iron(III) Oxide (Fe₂O₃) and have been asked to calculate how many moles are present in 24.6g of the compound whilst working out how many moles of Fe are present in this amount.

I have calculated the mole of Fe₂O₃ at 0.154 mol,
M= (Fe₂O₃), M= 2(55.8 ) + 3(16.0)
m = 24.6, M = 159.6, n = ?   so, n = m/M, 24.6/159.6 = 0.154mol

I cannot for the life of me grasp how to find out the mol of Fe in 24.6g this compound.
Do I divide the mol of Iron by the weight of the compound? Convert it to a percentage?

Any help would be greatly appreciated

Title: Re: How to calculate the mole of an element in a compound?
Post by: Hunter2 on December 10, 2013, 01:01:47 AM

its more easier.  You know the moles of the compound then you know also the moles of each atom. Its given to the formula. Example 1 mol NaCl  contain also 1 mol Na⁺ and 1 mol Cl^-. So how much is it for the iron oxide.

Title: Re: How to calculate the mole of an element in a compound?
Post by: Kommandante on December 10, 2013, 01:57:09 AM

Since the compound is 0.154 mol, does that mean there are 2(0.154)mol Fe?

Title: Re: How to calculate the mole of an element in a compound?
Post by: Hunter2 on December 10, 2013, 02:19:06 AM

Exactly. correct.

Title: Re: How to calculate the mole of an element in a compound?
Post by: Kommandante on December 10, 2013, 02:53:58 AM

Thanks for your help,
Greatly appreciated!