A compound containing only carbon and hydrogen is analyzed, and is found to contain 20.11% hydrogen on a mass basis. How can the empirical formula of the compound be calculated?

1 Answer
anor277
Dec 10, 2015

We assume 100 g of hydrocarbon. The empirical formula is the simplest whole number ratio that defines constituent atoms in a species.

Explanation:

In 100 g hydrocarbon, there are #(20.11*g)/(1.00794*g*mol^(-1)) = 19.95# #mol# #H#, and #(79.89*g)/(12.011*g*mol^(-1)) = 19.95# #mol# #C=6.65*mol# #C#.

We then divide thru by the lowest ratio to give the empirical formula, #CH_3#.

How did I know that #%C# was #79.89#?

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