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

1 Answer
Aug 14, 2017

Answer:

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.