Q. The 0.2 g of anhydrous organic acid gave on combustion 0.04 g of water and 0.195 g of $CO_2$. The acid is a dibasic acid and 0.5 g of its silver salt leaves on ignition 0.355 g of silver. The empirical weight of the compound is
Organic Chemistry – Some Basic Principles and Techniques
Solution:
% of carbon $= \frac{12}{44} \times \frac{0.195}{0.2}\times100 = 26.6$
% of hydrogen $= \frac{2}{18} \times \frac{0.04}{0.2} \times 100 = 2.22$
% of oxygen $= 100 - \left(26.6 + 2.22\right) = 71.18$
Element C H O % 26.6 2.22 71.18 %/At. wt. $\frac{26.6}{12} = 2.22$ $\frac{2.22}{1} = 2.22$ $\frac{71.18}{16} = 4.44$ Relative number of atoms $\frac{2.22}{2.22} = 1$ $\frac{2.22}{2.22} = 1$ $\frac{4.44}{2.22} = 2 $
Hence, empirical formula $= CHO_2$
Hence, empirical weight $= 12 + 1 + 32 = 45$
| Element | C | H | O |
|---|---|---|---|
| % | 26.6 | 2.22 | 71.18 |
| %/At. wt. | $\frac{26.6}{12} = 2.22$ | $\frac{2.22}{1} = 2.22$ | $\frac{71.18}{16} = 4.44$ |
| Relative number of atoms | $\frac{2.22}{2.22} = 1$ | $\frac{2.22}{2.22} = 1$ | $\frac{4.44}{2.22} = 2 $ |