How many moles are there in 9.0 grams of water?

0.5 moles

The approximate molecular mass of water can be determined by adding the atomic masses of the constituents (2 hydrogen atoms plus 1 oxgen atom) to get of 18 grams / mole (1 +1+16). Therefore if 1 mole of water has a mass of approximately 18 grams, then 9 grams of water contains 0.5 moles of water.