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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?

Answer 1

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

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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Answer 2

Cameron Andrews

Divide the mass percentage of each element by its molar mass to find the mole ratio, which is then divided by the smallest mole ratio to find the simplest whole-number ratio. This is how the empirical formula of the compound is calculated.

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Answer from HIX Tutor

When evaluating a one-sided limit, you need to be careful when a quantity is approaching zero since its sign is different depending on which way it is approaching zero from. Let us look at some examples.