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Homework Help: Am i in the right place?

  1. Sep 13, 2005 #1
    am i in the right place???

    i everyone i have a physics question but i am not sure if i am in the right place or not..... the question is:
    Estimate the number of water molecules in a raindrop 1.5 mm in radius.
    i really dont want you to solve it just give me the equation that i am supposed to use to solve the question.....

    and again.... if i am in the wrong place...please tell me where i am supposed to post this question

    thanks a lot
  2. jcsd
  3. Sep 13, 2005 #2


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    Gold Member

    This is better posted in the homework forum.

    Look up the molar volume of water. You'll find out how many atoms fit into a given volume. The rest is just volumetric calculation.
  4. Sep 13, 2005 #3


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    The density of water is 1 gram per cubic centimeter. The molecular mass of water is about 18 grams per mole. there are about 6.02*10^23 molecules in a mole. Assuming the raindrop is spherical, you can find its volume from [itex]V=\frac{4}{3}\pi r^3[/itex]. Using the desnity, you can find the mass, using the mass you can find the # of moles, using the # of moles you can find the # of molecules.
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