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Question
The percentage composition of sodium phosphate as determined by analysis is 42.1% sodium, 18.9% phosphorus and 39% oxygen. Find the empirical formula of the compound.
Solution
| Element | Atomic weight | % age | Relative number of moles | Simplest ratio of atoms |
| Na | 23 | 4.21 | `42.1/23` = 1.83 | `1.83/0.61` = 3 |
| P | 31 | 18.9 | `18.9/31` = 0.61 | `0.61/0.61` = 1 |
| O | 16 | 39 | `39/16` = 2.43 | `2.43/0.61` = 4 |
∴ Empirical formula is Na3PO4.
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