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Chemistry The Atomic Mass of M

  1. Feb 23, 2009 #1
    1. The problem statement, all variables and given/known data
    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?

    2. Relevant equations

    3. The attempt at a solution
    I dont not really know how to tackle this problem. I know the mass of MO2 would be 3.833g.
  2. jcsd
  3. Feb 24, 2009 #2


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    Your problem description indicates that 0.277 grams of M2S3 gave its stoichiometric amount of MO2. How do you know that the mass of MO2 is 3.833 grams as you say in your solution attempt? Your description does not give enough information for that. I might be missing something in my logic.
  4. Feb 24, 2009 #3


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    I think George means 3.733.

    George, start with a balanced reaction equation:

    M2S3 + O2 -> MO2 + SO2

    Try to express mass of MO2 produced in terms of masses and molar masses or reagents, that should give you one equation with one unknown - molar mass of M.
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