I need to find the amount of molecules in 4.5g of water. I only want to check my answer: 1.505 * 10^22 right?

Hydrogen has a molar mass of 1, and there is two of them H-2

Oxygen has a molar mass of 16, and there is only one O-16

So you must divide 4.5 by 18

which gives you 0.25

then you must times 0.25 by 6.022x10^23

and yes you get 1.505x10^23