Suppose you want a mixture that contains 2.5 grams of iron ion and three times as many moles of oxalate ion as moles of iron. If the iron comes from iron(iii)chloride and the oxalate ion from K2C2O4, how many grams of each of the compounds should you combine?

Answer 1

Note iron(III) is written with capital Is and not lower case is.
2.5 g Fe/55.85 = xx moles Fe you need. (I have rounded here. You should go through and be a little more accurate. I will round down the line, too, so it will be necessary for you to through all of the calculations for a better answer.) 3 x moles Fe = moles oxalate ions = ?? moles oxalate.
xx moles Fe x (1 mol FeCl3/1 mole Fe) = moles FeCl3 and that times molar mass = grams FeCl3.
?? moles oxalate x (1 mol K2C2O4/1 mole C2O4) = moles K2C2O4 and that times molar mass K2C2O4 = g K2C3O4.
Check my thinking. Check my work.

Answer 2

I made a typo, next to last line, should be molar mass K2C2O4 = g K2C2O4 instead of what follows.
molar mass K2C2O4 = g K2C3O4.
Check my thinking. Check my work.