I also taught Masters Students at Imperial for 3 years. The molecular formula for cyclohexane is C6H12, therefore one molecule of cyclohexane contains 6 carbon atoms and 12 hydrogen atoms. The relative atomic mass (RAM) of carbon is 12.011 g/mol. For hydrogen the RAM is 1.008 g/mol. Cyclohexane's molar mass is thus: (6 x 12.011) + (12 x 1.008) = 84.162 g/mol.