[kevvex]

How many gram iron is it in 150 gram Fe3O4 (The numbers after Fe and O are supposed to be lowered)

I think I have to use the formula m = M * n
but I don't know how to do that. I want to know
how many gram of Fe3 it is in Fe3O4 which
means I have to somehow remove the O4's right?

But I have no idea of how to remove them so that
I only get Fe3's left? I bet someone on here knows.

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Mod addition for clarity using the subscript feature in the posting window
Fe₃O₄

[AWK]

This is a simple stoichiometric problem based on chemical formula
Check textbook or internet sources, eg:
http://www.sparknotes.com/chemistry/stoichiometry/stoichiometriccalculations/section2.rhtml

[Arkcon]

What would 4 `O`s weigh?  What would 3 `Fe`s weigh?  How would you find out?  How much of 150 g Fe₃O₄ is Fe?

You can use these hints to begin to understand the problem, and be ready for anything, come exam time.

[tumblewush]

Hey there, kevvex Going to try my best with my first ever attempt of helping out in this forum.

There's actually no need to remove any of the O's  You just have to look at your compound as one big unit, and the periodic table's going to be your best friend here of course 

The first question that you have to ask yourself here here is "How much does a single molecule of my Fe₃O₄ weigh?". Then you'll be following that up with "Of that weight of a single molecule, how much of the whole is iron?". When you can answer that second question, all that's left is to ask yourself "Now that I know how much of a single molecule is Fe, given I have 150 g of my compound, how much of it is going to be iron?".

Hope I helped out.