# A hydrocarbon has an empirical formula of CH_2, and a molecular mass of 42*g*mol^-1. What is the hydrocarbon?

Sep 18, 2017

Well we got propylene or cyclopropane.....i.e. ${C}_{3} {H}_{6}$....

#### Explanation:

The molecular formula is always a whole number multiple of the empirical formula....

And thus ...........

${\underbrace{12.01 \cdot g \cdot m o {l}^{-} 1 + 2 \times 1.01 \cdot g \cdot m o {l}^{-} 1}}_{\text{empirical formula"xxn=underbrace(42*g*mol^-1)_"molecular mass}}$

And so $n = \frac{42.0 \cdot g \cdot m o {l}^{-} 1}{12.01 \cdot g \cdot m o {l}^{-} 1 + 2 \times 1.01 \cdot g \cdot m o {l}^{-} 1} = 3$

And so the molecular formula is $3 \times C {H}_{2} \equiv {C}_{3} {H}_{6}$....and this is either propylene, ${H}_{3} C - C H = C {H}_{2}$ or $\text{cyclopropane}$.