Question

An organic compound containing $C$ and $H$ gave the following analysis: $C=40\%,H=6.7\%$ and the remaining, oxygen. Its empirical formula would be:

• A. $C{H}_4$
• B. $C{H}_{2}O$
• C. $C_2{H}_{3}O$
• D. $C_2{H}_4$

Answer 1

The correct option is B $C{H}_{2}O$

Calculation of empirical formula:
% of oxygen will be $[100-(40+6.7\left)\right]\%=53.3\%$

$\begin{array}{ccccc}\text{Element}& \text{\% in compound}& \text{Atomic mass}& \text{No. of moles}& \text{Simple ratio}\\ C& 40& 12& \frac{40}{12}=3.33& \frac{3.33}{3.33}=1\\ H& 6.7& 1& \frac{6.7}{1}=6.7& \frac{6.7}{3.33}=2\\ O& 53.3& 16& \frac{53.3}{16}=3.33& \frac{3.33}{3.33}=1\end{array}$

So, the empirical formula is $C{H}_{2}O$