# Am i in the right place?

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

Related Introductory Physics Homework Help News on Phys.org
DaveC426913
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.

LeonhardEuler
Gold Member
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.