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Homework Help: Relative molecular mass using unified mass unit

  1. Jan 18, 2012 #1
    The problem
    A bubble of kryptopn (Kr) gas is formed underwater. The bubble has a volume of 2.14x10-6m3 and contains 1.70x1020 krypton molecules each of mass 1.39x10-25kg. The pressure of the gas inside the bubble is 300kPa.

    Calculate the relative molecular mass.

    The attempt at a solution

    When i looked in the markscheme of this paper, the answer was Mr=1.39x10-25/1.66x10-27 as the answer. so does this mean to find the relative molecular mass i divide the mass by the unified mass unit?
  2. jcsd
  3. Jan 18, 2012 #2
    What you have calculated is the mass of a Krypton atom in amu (Atomic Mass Units)
    = 83
  4. Jan 18, 2012 #3
    is that the same as the relative molecular mass? what i worked out is what the markscheme had written as the result.
  5. Jan 19, 2012 #4
    I have asked a chemistry teacher friend and he said relative molecular mass is given in grams per mole4
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