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Homework Help: Is this right

  1. Jul 30, 2009 #1
    A substance consists of equal numbers of tow kinds of atoms, with masses m1 and m2 respectively.
    a) what is the mass of the substance is 2x106 atoms of each kind are present, where m1 = 3.4x10-26kg and m2 = 1.6x10-26kg?
    3.4x10-26kg + 1.6x10-26kg = 5x10-26 x 2x106 = 1x10-19kg

    b) how many atoms are there altogether (counting both kinds) in 1kg of the substance?
    1kg / 5x10-26kg = 2x1025atoms

    is this correct
  2. jcsd
  3. Jul 30, 2009 #2


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    (a) looks good.

    For (b), note that 5x10-26kg is the mass of a pair of atoms. So there are 2x1025 pairs of atoms.
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