Question

Diacetyl, a substance contributing to the characteristic flavor and aroma of butter, consists of 55.8% C, 7.03% H, and 37.17% O. In the gaseous state at 100 degrees celsius and 747 torr, a 0.30 gram sample occupies a volume of 111 ml. What is the molecular formula of diacetyl?

Answer 1

Take 100 grams sample.
That gives you
55.8 g C
7.03 g H
37.17 g O

Convert to moles
55.8/12 = 4.65 moles C
7.03/
37.17/

Now find the ratio of these numbers to each other using small whole numbers. The easy way to do that is to divide the smallest number by itself, then divide all of the other numbers by the same small number. This gives you the empirical formula.

Now use PV = nRT to determine n.
Then n = grams/molar mass
Calculate molar mass and from there the molecular formula.
Post your work if you get stuck.

Answer 2

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