An environmental chemist analyses treated wastewater from a pharmaceutical synthesis facility. The fluid has been filtered and is completely clear and colourless. The analysis of the water is shown in the table below:
| Substance | Concentration in mg/dm³ |
|---|---|
| Ammonium ions (NH4+NH_4^+NH4+) | 12 |
| Phosphate ions (PO43−PO_4^{3-}PO43−) | 8 |
| Methanol (CH3OHCH_3OHCH3OH) | 2 |
| pH | 6.8 |
Explain why this treated water sample should be classified as a mixture rather than a chemically pure substance.
