Question

The empirical formula of a compound is $C{H}_2$. One mole of this compound has a mass of $42$ g. Its molecular formula is:

• A. $C{H}_2$
• B. $C_2{H}_2$
• C. $C_3{H}_6$
• D. $C_3{H}_8$

Answer 1

Answer: (C)

$C_3{H}_6$

The empirical formula is $C{H}_2$. Therefore, the empirical weight $=$ $14$.
Given, the molecular weight $=42$ g.

$x=\frac{\text{Molecular weight}}{\text{Empirical weight}}=\frac{42}{14}=3$

$\text{Molecular Formula}=(\text{Empirical Formula}{)}_x$

$\therefore \text{Molecular Formula}=(C{H}_2{)}_3=C_3{H}_6$