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
