The molecular mass of water, H2O: = (2 × Atomic mass of hydrogen) + (1 × Atomic mass of oxygen) = [2(1.0084) + 1(16.00 u)] = 2.016 u + 16.00 u = 18.016 = 18.02 u The molecular mass of carbon dioxide, CO2: = (1 × Atomic mass of carbon) + (2 × Atomic mass of oxygen) = [1(12.011 u) + 2 (16.00 u)] = 12.011 u + 32.00 u = 44.01 u (c) CH4 The molecular mass of methane, CH4: = (1 × Atomic mass of carbon) + (4 × Atomic mass of hydrogen) = [1(12.011 u) + 4 (1.008 u)] = 12.011 u + 4.032 u = 16.043 u