water is h2o, so the molar mass is 1.01x2+16.00=18.02. divide 4.5 x 10^22 by 6.022 x 10^23 to get 7.5 x 10^-2 (2 sig figs). 18.02 x 7.5 x 10^-2 is 1.35 g
I'm not sure about part 1, you may need to google it, but part two is 11 protons, 11 electrons and 12 neutrons. You can find protons and electrons by just looking at the atomic number, and you can find neutrons by subtracting the atomic number from the atomic mass.
