Question
Silicon (Si = 28) forms a compound with chlorine (Cl = 35·5) in which 5·6g of silicon is combined with 21·3g of chlorine. Calculate the empirical formula of the compound.
Solution
(i) To calculate the percentage of silicon and chlorine:
Weight of silicon = 5.6 g
Weight of chlorine = 21.3 g
(ii) To calculate the empirical formula:
| Element | % | atomic no. | atomic ratio | simplest ratio | simple whole ratio |
| Silicon | 20.8 | 28 | 20.8/28=0.74 | 0.74/0.74=1 | 1 |
| Chlorine | 79.2 | 35.5 | 79.2/35.5=2.23 | 2.23/0.74=3 | 3 |
Therefore empirical formula is SiCl3.
