Chemistry

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A rock is 5.0% by mass fayolite(Fe2SiO4), 7.0% by mass forsterite(Mg2SiO4) and the remainder silicon dioxide. What is the mass percent of each element in the rock?

I have the answers but i don't know how to solve the problem.

How would you in steps solve the problem?

• Chemistry -

I would take a 100g sample which will give you 5.0g of the iron compound, 7.0g of the Mg compound, and 88g SiO2.
5.0g x %Fe in the iron compound = g Fe.
7.0g x %Mg in the Mg compound = g Mg.
%Fe = (gFe/100g)*100
%Mg = )gMg/100g)*100
For Si, compute g Si in the iron cmpd and add to g Si in the Mg cmpd and add to g Si in the SiO2. %Si is done the same way as the others.
I'm sure you get the idea for oxygen.

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