Combustion of 493 mg of a hydrocarbon gave 1549 mg CO₂ and 633.9 mg H₂O.What is the molecular formula if the molecular weight is subsequently found to be 42?

Question

Quizplus · Accepted Answer

The combustion analysis shows the hydrocarbon has a molar mass of 42 g/mol. The empirical formula from the combustion data is CH2, which has a molar mass of 14 g/mol. The molecular formula is a multiple of the empirical formula, and 42/14 = 3, so the molecular formula is C3H6.

Combustion of 493 Mg of a Hydrocarbon Gave 1549 Mg