Question

The problem ask what is the mass of iron(iii) chloride contains 2.35 x 10^23 chloride ions.

I understand the molar mass is 162.20 g/mol.
- 2.35 x 10^23 chloride ions would be around 0.39 moles.
- The work that my teacher gave me is
0.39 moles * (1 mol FeCl3 / 3 mol chloride ions) * (162.20 g FeCl3 / 1 mol FeCl3)

-What I don't understand is how is why is the moles of chloride ions being *(1 mol FeCl3 / 3 mol chloride ions)- Could someone explain this to me? Thanks

Answer 1

FeCl3 is iron chloride. There is only 1 mol Fe for every 3 mol Cl ions (and only 1 mol FeCl3 for every 3 mol Cl ions); therefore, you must divide mols Cl by 3 to get mols FeCl3 or mol Fe. If I asked you how many Cl ions I had for 2 atoms Fe in FeCl3, you would immediately tell be 2*3 = 6 because you see 3 cl for every 1 Fe. This is just the reverse of that.

Answer 2

Thank you so much for that explanation!

Answer 3

For every mole of FeCl3, you have 3 moles of chlorine. There is only one FeCl3, but in that one FeCl3, there are three Cl's. That is why the ratio is 1 mole of FeCl3=3 moles of FeCl3, or 1 mol FeCl3/3 mol chloride ions.