Please help me with this AP CHEM TEXTBOOK QUESTION!!

<p>Here's the question from "Chemistry" by Chang 8th edition. It's from the end-of-chapter questions on Chapter 3.</p>

<p>"A sample containing NaCl, Na2SO4, and NaNO3 gives the following elemental analysis:</p>

<p>Na: 32.08 %
O: 36.01%
Cl: 19.51%</p>

<p>Calculate the mass percent of each compound in the sample."</p>

<p>So I converted all the %'s to grams and found there are these many moles:</p>

<p>32.08 g Na = 1.395 mols Na
36.01 g O = 2.251 mols O
19.51 g Cl = 0.5503 mol Cl</p>

<p>From there I realized that all the mols of Cl must be part of NaCl, seeing as that's the only substance w/Cl. So Now, .5503 mol of Na and Cl are consumed.</p>

<p>So here's the problem that I'm stuck with: how to find the remaining grams of the 2 other substances? I can't just divide the remainder of the mols of Na into 3 and equally distribute them because I don't know if there should be the same amount of Na in those 2 substances. </p>

<p>I'm very confused with this problem and it's due MONDAY MORNING (at 9 am EST). So if ANYONE could help me or even give me some advice I would truly appreciate it!</p>