# Question #589aa

Mar 29, 2017

Dividing the given percentage of C and H with their respective atomic masses and taking their ratio we get the ratio of number of atoms of the elements present in the compound.

So the ratio of number of atoms of C and H in the compound will be

${n}_{C} : {n}_{H} = \frac{84.21}{12} : \frac{15.79}{1} = 7.0175 : 15.79$

$= 1 : \frac{15.79}{7.0175} = 1 : 2.25 = 4 : 9$

Hence the empirical formula of the compound is ${C}_{4} {H}_{9}$

let its molecular formula be ${\left({C}_{4} {H}_{9}\right)}_{n}$

So calculated value of molar mass will be $\left(12 \times 4 + 1 \times 9\right) n = 57 n g \text{/} m o l$

But given molar mass is $114 g \text{/} m o l$

Hence $57 n = 114 \implies n = 2$

So molecular formula of the hydrocarbon is ${C}_{8} {H}_{18}$