What is the empirical formula for this compound?

Question

A hydrocarbon (a compound consisting solely of carbon and hydrogen) is found to be 85.6% carbon by mass. What is the empirical formula for this compound?

Answer 1

Assume a 100g sample

85.6 grams C x (1 mol C / 12.0g C) = 7.13 mol C

14.4 grams H x (1 mol H / 1.01 g H) = 14.3 mol H

Divide each by 7.13

C = 1 mol

H = 2 mols

The empirical formula is CH2

Answer 2

The compound has only carbon and Hydrogen. If carbon is 85.6% than Hydrogen is 14.4% because they all constitute 100%.

Empirical formula:

We know the at. weight for carbon is 12g/mole and it is Carbon is 85.6 g in this compound

So, 12 g consist of 1 mole

than 85.6 g consist of (85.6/12) = 7.13 mole

Similarly for hydrogen = 14.1/1 = 14.4 mole

second step to find empirical formula is to divide by lowest

C = 7.13/7.13 = 1

H = 14.4/7.13 = 2.01

So empirical formula for this compound is CH2

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