You need to work out the balanced equation for the reaction between permaganate and iron, this will then give you the mole ratio. use the mole ratio to find the number of moles of iron in the conical flask.
Then multiply this up to the size of the volumetric flask (eg if you used 25cm3 samples in the conical flask, then the no of moles in the volumetric flask would be 10x more).
Then use mass = moles x atomic mass to find the mass of iron
and divide by the mass of the hydrated crystals and x100 to get percentage
I'm pretty sure that's the method, but I'm not 100% clear on some of your steps above. I hope that helps.
Thanks I figured out the balanced equation 5 Fe2+(aq) + MnO4-(aq) + 8H+(aq)=5Fe3+(aq) + Mn2+(aq) + 4H2O(l)
Sorry but what is the mole ratio and how do you use the mole ratio to find the number of moles of iron in the conicle flask?
In your balanced equation you have written that 5 moles of iron react with 1 mole of permanganate - this is the mole ratio, therefore multiply the no of moles of permanganate by 5 to get the number of moles in the conical flask.
But if I got 1.50 mol for example in the conicle flask would that mean I would have to devide 250 by 1.50 to work out the number of moles in the 250cm3 solution?
At this point you just scale up the volumes, so if the conical flask contains 25cm3 of your solution, then the volumetric flask would have contained 10x more, so the number of moles in the volumetric flask would be 1.5 x10 = 15 moles.
Yes it would be. Are you sure your number is 15? It's normally less than 1 when done on a laboratory scale (the examples when they make you work in tonnes naturally are much bigger!). Remember when working out number of moles in a solution we have to change the volume into dm3 - you do this by dividing the cm3 by 1000.