Arithmetic help in chemistry

  1. ok, i'm trying to get the mass of a calcium atom in kilograms...formula for converting atoms to grams is(1.00amu=1.66x10^-24g)Calcium is 40.1amu
    Ok, here is the setup with it..
    40.1amu/1 x 1.66x10^-24g/1.00amu x 1kg/1,000g= ...
    So how am i suposed to get the answer? Could someone please put the answer our step by step for me? Thanks a bunch:smile:

  2. jcsd
  3. ShawnD

    ShawnD 953
    Science Advisor

    The main thing is to get the units to work out.

    40.1amu * 1.66x10^-24g/amu * 1kg/1000g = 6.6566x10^-26kg

    The way we did questions like this at my school was like this:
    40.08g/mol * 1mol/6.02x10^23atoms * 1kg/1000g = 6.6578x10^-26kg/atom

    Both ways work but I personally like the second way better. 6.02x10^23 is avogadro's number which is fairly easy to remember since you see it a lot. That 1.66x10^-24 is 1 over avogadro's number which does the same thing in both equations but it just makes it so you need to remember another number (not a good thing).
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