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Question
A compound of lead has following percentage composition, Pb = 90.66%, O = 9.34%. Calculate empirical formula of a compound. [Pb = 207, O = 16]
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Solution
Empirical formula of a compound:
| Element | Atomic mass |
Percentage | Relative number of | Simplest mole ratio | Whole number ratio |
| Pb | 207 | 90.66 | 90.66/207 = 0.44 | 0.44/0.44 = 1 | 1 x 3 = 3 |
| O | 16 | 9.34 | 9.34/16 = 0.58 | 0.58/0.44 = 1.32 | 1.32 x 3 = 3.96 = 4 |
Since the mole ratio for oxygen is fractional so we multiply the whole ratio by 3 to make i t a whole number.
So, the empirical formula of the compound is Pb3O4.
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