A hydrocarbon has 80% carbon content. What is its empirical formula?

1 Answer
anor277
Aug 14, 2017

If the hydrocarbon has 80% carbon content, then the empirical formula is CH_3.

Explanation:

We assume a mass of 100*g of stuff...

"Moles of carbon"=(80.0*g)/(12.011*g*mol^-1)=6.67*mol.

"Moles of hydrogen"=(20.0*g)/(1.00794*g*mol^-1)=19.84*mol.

We divide thru by the smallest quantity, i.e.

C:(6.67*mol)/(6.67*mol)=1

H:(19.84*mol)/(6.67*mol)=3

So our empirical formula is CH_3. In fact, this is consistent with a molecular formula of C_2H_6, i.e. "ethane". The question might have asked this, had they quoted a proper value for molecular weight.

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