Determine the number of moles 1) 20g Na and 2) 34g H2O

To calculate this, add up the automic mass units of each atom. (That can be found under the element's abbreviation on the periodic table.)

1) Na = 23 amu

20g / 23 = 0.87 moles Na

2) H = 1.01 O = 16.0

1.01 + 1.01 + 16 = 18.02

34g/18.02 = 1.89 moles H2O