How many moles of water, H2O, contain 2.0×1022 molecules of water? (See the hints for assistance in interpreting scientific notation.)
Express the quantity in moles to two significant figures.
You have to use Avogadro's number which is 6.02x10^23. The units of Avogadro's number is molecules/mole so you divide the number of molecules by Avogadro's number which will give you the number of moles. (2.0x10^22 molecules)/(6.02x10^23 molecules/mole)=0.033 moles
