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Homework Help: Need to identify mysterious element

  1. Mar 7, 2007 #1
    1. The problem statement, all variables and given/known data
    An element X forms both a dicholride( XCl2) and tetrachloride(XCl4). Treatment of 10.0g of XCl2 with excess forms 12.55g of XCl4. Calculate Atomic Mass of X and Identify X

    2. Relevant equations
    no equation needed...but urgent

    3. The attempt at a solution

    i try subtracting 12.55g of XCL4 with 10.0g of 10.0g of XCL2
    and i am lost at what is the EXCESS, is that CL2 ?

    if it is...then i have 2.55g/ 71g CL2 = 0.359mole of CL2. basically i am lost
  2. jcsd
  3. Mar 7, 2007 #2


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    Do you get the equation

    [tex] \frac{10}{x+71}=\frac{12.55}{x+142} [/tex] ?
  4. Mar 7, 2007 #3
    thank you, i never realize i just have to use cross multiply. i see ur work as x+CL2(71) = x+Cl4(142)
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