You are given a liquid sample that contains either methanol (CH₃OH), ethanol (CH₃CH₂OH), or a mixture of both. You use combustion analysis of a 0.336 g sample and obtain 0.462 g of CO₂. What did you learn about your sample? A)It is methanol. B)It is ethanol. C)It is more methanol than ethanol. D)It is more ethanol than methanol. E)It contains equal amounts of methanol and ethanol.

Question

Quizplus · Accepted Answer

The combustion analysis shows that the sample contains carbon and hydrogen. The ratio of CO₂ to H₂O produced in the combustion is 1:1, which indicates that the sample is an alcohol. The molecular weight of methanol is 32 g/mol, and the molecular weight of ethanol is 46 g/mol. The sample weight is 0.336 g, and the weight of CO₂ produced is 0.462 g. The number of moles of CO₂ produced is 0.462 g / 44 g/mol = 0.0105 mol. The number of moles of carbon in the sample is 0.0105 mol. The number of moles of hydrogen in the sample is 2 x 0.0105 mol = 0.021 mol. The empirical formula of the sample is CH₂O. The molecular weight of CH₂O is 30 g/mol, which is close to the molecular weight of methanol (32 g/mol). Therefore, the sample is most likely methanol.

You Are Given a Liquid Sample That Contains Either Methanol