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Homework Help: Pleas help! Chemistry calculations

  1. Apr 30, 2006 #1

    Aya

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    the folowing reaction proceeds with a 70% yeild

    C6H6 + HNO3 = C6H5NO2 + H2O

    calculate the mass of C6H5NO2 expected if 12.8g of C6H5 reacts with excess HNO3

    How do you do this problem?
     
  2. jcsd
  3. Apr 30, 2006 #2
    I'm no expert, but this was what I think:

    The number of moles of C6H6 can be calculated (mass/Mr), and since 1 mole of reactant produces 1 mole of product and the reaction is only 70% "efficient", means that the number of moles of the product is 0.7 times the number of moles of the C6H6, and so from this, simply multiply by the Mr of the C6H5NO2 to get the result.

    btw, the excess bit tells you that all 12.8g of C6H6 reacts.
     
  4. Apr 30, 2006 #3

    Aya

    User Avatar

    ^ Thanks

    #mols of C6H6

    n=m/M
    n=12.8g/78.06g/mol
    n=0.164mol


    #mols of C6H5NO2

    =0.164mol(0.70)
    =0.1148mol

    mass of C6H5NO2

    m=nM
    m=0.1148mol(123.06g/mol)
    m=14.1g

    Like this?
     
  5. Apr 30, 2006 #4

    Aya

    User Avatar

    and I have another question

    If 3.45 x 10^23 formula units of Hg(NO3)2 are reacted with excess of Na2S, what mass of HgS can be expected if this process occurs with 97% yield?


    What are fomula units?

    you would do that question the same way as the previous one right?
     
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