Am i in the right place?

1. Sep 13, 2005

mh922253

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. Sep 13, 2005

DaveC426913

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.

3. Sep 13, 2005

LeonhardEuler

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 $V=\frac{4}{3}\pi r^3$. 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.