Question

A compound with the empirical formula CH 2 CH2 has a molar mass of 126 126 g/mol. What is the molecular formula for this compound?

Answer 1

Answer: The molecular formula of the compound is $C_9H_{18}$

Explanation:

We are given:

Empirical formula of the compound = $CH_2$

For determining the molecular formula, we need to determine the valency which is multiplied by each element to get the molecular formula.

The equation used to calculate the valency is :

$n=\frac{\text{Molecular mass}}{\text{Empirical mass}}$

We are given:

Mass of molecular formula = 126 g/mol

Mass of empirical formula = $12+(2\times 1)]=14g/mol$

Putting values in above equation, we get:

$n=\frac{126g/mol}{14g/mol}=9$

Multiplying this valency by the subscript of every element of empirical formula, we get:

$C_{(9\times 1)}H_{(9\times 2)}=C_9H_{18}$

Hence, the molecular formula of the compound is $C_9H_{18}$