Compound A consisting of carbon and hydrogen only. The compound was found to contain 80% carbon by mass,cal. its empiri.

Answer 1

assume you have 100grams total
so there is 80 gramsC
and 20gH
lets look at moles
C 80/12=6.666
H 20/1=20

so the mole ratio then is (divide the lessor number into each ...
C 1
H 3

CH3 is the empirical formula