Help with determination of water molecules?

[pcatgirl]

For my lab, I have to figure out the number of water molecules that are present in K3Fe(C2O4)3 nH20 for every iron atom with the percentage of oxalate. I found my percentage which is 43.36%. I'm having trouble of where to start.

 

Please Help

 

PS- Let me know if you need any extra information

Edited April 27, 2010 by pcatgirl

[Fuzzwood]

I assume this percentage is a percentage of the total mass. If so, you also have the mass of your sample before and after the drying.

 

You can now state that the mass of the sample after drying is equivalent to the amount of moles of K₃Fe(C₂O₄)₃ times it's molar mass. So with many moles of K₃Fe(C₂O₄)₃ did you start out?

 

You also have the mass of the water you removed. How many moles of water does that give you?

 

Now you know the ratio of moles of water:moles of K₃Fe(C₂O₄)₃.

 

If you can calculate that to the ratio of moles of water:1 mole of K₃Fe(C₂O₄)₃, you are done