easy chemistry question?

Discussion in 'Community Discussion' started by macman2790, Jun 20, 2007.

  1. macman2790 macrumors 6502a

    macman2790

    Joined:
    Sep 4, 2006
    Location:
    Texas
    #1
    im having trouble with this one, im trying to figure out if the answer is eleven or 4.

    How many oxygen atoms are represented by MgSO4•7H2O?

    thanks
     
  2. killr_b macrumors 6502a

    killr_b

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    Suckerfornia
    #2
    I see five, unless you are combining and lose one.
     
  3. furcalchick macrumors 68020

    furcalchick

    Joined:
    Dec 19, 2006
    Location:
    South Florida
    #3
    11

    seven water molecules, one oxygen in each of them, plus four from the other substance.
     
  4. lancestraz macrumors 6502a

    lancestraz

    Joined:
    Nov 27, 2005
    Location:
    RI
    #4
    Yup, it's eleven.
     
  5. macman2790 thread starter macrumors 6502a

    macman2790

    Joined:
    Sep 4, 2006
    Location:
    Texas
    #5
    thanks, sorry but i actually have one more, im not sure how to figure out this one, but i think its 5.2

    How many moles of CH3NH2 are in 6.0 g

    thanks again
     
  6. furcalchick macrumors 68020

    furcalchick

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    Dec 19, 2006
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    South Florida
    #6
    yeah, it's 5.2.
     
  7. mikes63737 macrumors 65816

    Joined:
    Jul 26, 2005
    #7
    Unless I misread the problem, CH3NH2 is 31g/mole. 6 grams is 0.2 moles, not 5.2. You just divided the wrong way. :)
     
  8. Hummer macrumors 65816

    Hummer

    Joined:
    Feb 3, 2006
    Location:
    Queens, New York NY-5
    #8
    Sounds like an answer I got on my Regents today.
     
  9. furcalchick macrumors 68020

    furcalchick

    Joined:
    Dec 19, 2006
    Location:
    South Florida
    #9
    oops.
     
  10. Jasonbot macrumors 68020

    Jasonbot

    Joined:
    Aug 15, 2006
    Location:
    The Rainbow Nation RSA
    #10
    number of moles=mass/molar mass
    x=6/31
    x=0.193 moles
     

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