Q. An organic compound contains $40\%C, 6.66\%\, H$ and rest oxygen. Its vapour density is $30$. What will be its empirical formula?
UP CPMTUP CPMT 2011Some Basic Concepts of Chemistry
Solution:
Calculation of empirical formula:
Element
Percentage
At. mass
Relative number of atoms
Simplest ratio
Carbon
$40.0$
$12$
$\frac{40}{10}=3.33$
$\frac{3.33}{3.33}=1$
Hydro gen
$6.66$
$1$
$\frac{6.66}{1}=6.66$
$\frac{6.66}{3.33}=2$
Oxygen
$53.34$ (by difference)
$16$
$\frac{53.34}{16}=3.33$
$\frac{3.33}{3.33}=1$
Empirical formula - $CH_2O$
| Element | Percentage | At. mass | Relative number of atoms | Simplest ratio |
| Carbon | $40.0$ | $12$ | $\frac{40}{10}=3.33$ | $\frac{3.33}{3.33}=1$ |
| Hydro gen | $6.66$ | $1$ | $\frac{6.66}{1}=6.66$ | $\frac{6.66}{3.33}=2$ |
| Oxygen | $53.34$ (by difference) | $16$ | $\frac{53.34}{16}=3.33$ | $\frac{3.33}{3.33}=1$ |