Question

Determine the molecular weight of H2O.

18 g
18.0 g
18.01 g
18.016 g

Answer 1

The sum of their atomic mass multiplied by numbers of atoms.

That means
\([2 \times (\color{red}{mass~of~hydrogen})] + [1 \times (\color{blue}{mass~of~oxygen})]\)

Answer 2

the atomic mass of oxygen is 16 and the mass of hydrogen is 1. Because its H2 you need 2 hydrogen... the grand total of both Oxygen and hydrogen is 18...therefore you need 18 grams of water.

Answer 3

actually, it is 15.99 for oxygen, and 1.008 for hydrogen.

Answer 4

according to my textbook the atomic mass of Oxygen is 16 and exactly 16 and hydrogen is 1.01. LOL let the guy figure out the rest.