# What is the molecular formula of each compound CH2 with molar mass 42.08 g/mol?

Jul 8, 2018

Don't we got ${C}_{3} {H}_{6}$...I,e, probably propylene...

#### Explanation:

The $\text{empirical formula}$ is the simplest, whole number ratio defining constituent atoms in a species. The $\text{molecular formula}$ is a whole number multiple of the $\text{empirical formula}$, and of course the multiple MIGHT be ONE.

And thus...."molecular formula"=nxx{"empirical formula"}

And we take the relevant masses...

$\left[\left(2 \times 12.011 + 4 \times 1.00794\right) \cdot g \cdot m o {l}^{-} 1\right] \times n \equiv {\underbrace{42.08 \cdot g \cdot m o {l}^{-} 1}}_{\text{given molecular mass}}$

And so we solve for $n$ by the quotient....

$n = \frac{42.08 \cdot g \cdot m o {l}^{-} 1}{1 \times 12.011 + 2 \times 1.00794 \cdot g \cdot m o {l}^{-} 1} = 3$

And so our molecular formula is $3 \times C {H}_{2} \equiv {C}_{3} {H}_{6}$...this is propylene, or cyclopropane...