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Homework Help: Finding mole and name of elements

  1. Jun 5, 2010 #1
    1. The problem statement, all variables and given/known data
    a sample of 0.6 moles of a metal M reacts completely with excess of flourine to form 46.8 gms of MF2.
    a)how many moles of F are present in the sample of MF2 that forms?
    b)which element is represented by the symbol M?


    2. Relevant equations
    NO. OF MOLES=given mass/molar mass


    3. The attempt at a solution
    molesof element M:moles of compound formed MF2
    1 : 1
    0.6 : 0.6
    1 mole of MF2 contains 2 moles of F
    0.6 MOLES WOULD CONTAIN=0.6*2=1.2

    now i dnt no how can i find which element it is
     
  2. jcsd
  3. Jun 5, 2010 #2

    Borek

    User Avatar

    Staff: Mentor

    Think how you can calculate its molar mass from the information given.

    --
    methods
     
  4. Jun 5, 2010 #3
    i tried my best i m nt getting which formula to use
     
  5. Jun 5, 2010 #4
    A little more: how much MF2 do you have at the end of your reaction?
     
  6. Jun 6, 2010 #5
    total MF2=46.8GMS
    atomic mass of flourine=19 g/mol
    mass=moles*atomic mass
    =0.6*19
    = 22.8gms
    hence
    mass of element M=46.8-22.8
    =24gms
    molar mass of element M=mass of M/moles of M
    =24GMS/0.6
    =40 g/mol
    atomic mass of element M=40g/mol
    this is atomic mass of calcium
     
  7. Jun 6, 2010 #6
    so the element is calcium

    thnx a lot for ur help
     
  8. Jun 6, 2010 #7

    Borek

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    Staff: Mentor

    Wasn't that hard :wink
     
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