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Homework Help: Mass to Volume Problem

  1. Dec 9, 2007 #1
    [SOLVED] Mass to Volume Problem

    I have a mass to volume sample problem in my textbox and the answer seems to be wrong. Could someone please look this over and let me know if the answer to the sample problem is in fact wrong?
    Thanks very much!!


    What volume of H2(g) at STP can be produced when 10.0g of calcium is reacted with excess water?

    Ca(s) + 2 H2O(l) -> Ca(OH)2(s) + H2(g)

    1. Balance the equation: Ca + 2 H2O -> Ca(OH)2 + 2 H2
    (Where does the 2 in 2 H2 come from? This is an unbalanced equation.)
    2. Find the moles of Ca reacted: mol Ca = 0.2494mol
    3. Proportionality: x/2 = 0.2494mol/1 for which x = 0.4988mol
    (Again the 2 from 2 H2 is used here, which is why I think the answer is wrong.)
    4. Volume of H2: 0.4988mol x 22.4L/mol = 11.2L
    (Shouldn’t the answer be 5.59L?)
    Last edited: Dec 9, 2007
  2. jcsd
  3. Dec 9, 2007 #2
    I agree with you, there should not be a 2 infront of H2 in the equation and the answer should be 5.59L
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