Hard Chemistry Questions..Please help!

Test Preparation
1

<p>If anyone can do these questions, can you please show me?</p>

<li><p>When M2S3 is heated in air, it is converted to MO2. A 4.000g sample of M2S3 shows a decrease in mass of .277 g when it is heated in air. What is the average atomic mass of M?</p></li>
<li><p>A 1.500 g sample of a mixture containing only Cu2O and CuO was treated with hydrogen to produce 1.252 g pure copper metal. Calculate the percentage composition (by mass) of the mixture.</p></li>
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<p>The answer to question 2 is 40.0 and 60.0 percent respectively, I have no idea how that came to be.</p>

<p>Thank you in advance for help! :slight_smile: :)</p>

2

<p>is that for the SAT Subject test for Chemistry, b/c they seem a lot harder to me than the ones I recently took last June. They remind me more of AP questions. But, if you still need help, feel free to PM me and I'll try to work them out for you. Even though it's only been like two months since I took chemistry, i forgot a lot. :P</p>