Barrons SAT Subject Test Chemistry, 13th Edition

(T, T, CE) One mole of each of the substances contains 6.02 × 10^23
molecules, but their molecular masses are different. CO 2 is found by adding
one C = 12 and two O = 32, or a total of 44 amu. The H 2 O, however, adds up
to two H = 2 plus one O = 16, or a total of 18 amu. Thus, it is true that 1 mol
of CO 2 at 44 g/mol is heavier than 1 mol of H 2 O at 18 g/mol.