How Many Water Molecules Are in a 1.5 mm Raindrop?

[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 don't 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

 

[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.

 

[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.