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An organic substance is found to have 49.3% carbon and 6.84% hydrogen by mass. If its vapour density is 73, what is its molecular formula?

1. C₃H₆O₂
2. C₄H₁₀O₂
3. C₆H₁₀O₄
4. C₃H₁₀O₂

Correct answer: C₆H₁₀O₄

Solution

C:H:O = 49.3/12 : 6.84/1 : 43.86/16 = 1.5:2.5:1 = 3:5:2 -> empirical C3H5O2 (73); MW 146 doubles it to C6H10O4. Stored C4H10O2 (90) is wrong.

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