Ferrous sulphate solution is typically light green.
Ferrous sulphate is a common chemical compound, and its appearance varies depending on its hydration state. The color observed in an aqueous solution is primarily due to the presence of hydrated ferrous ions (Fe²⁺).
Understanding Ferrous Sulphate Colors
The color of ferrous sulphate is closely related to the presence or absence of water molecules in its structure. The provided reference highlights this distinction:
- The colour that ferrous sulphate crystals (FeSO4. 7H2O) exhibit is light green. This heptahydrate form is the most common crystalline state and readily dissolves in water to form a solution. The light green color of the crystals is characteristic of the hydrated ferrous ions.
- On heating, the water in the crystals evaporates, resulting in the formation of anhydrous ferrous sulphate (FeSO4), which changes the crystals' colour from light green to white. Anhydrous ferrous sulphate contains no water and its color is different from the hydrated forms.
When ferrous sulphate crystals (FeSO4.7H2O) are dissolved in water, the hydrated ferrous ions (Fe²⁺(aq)) are released into the solution. These hydrated ions are responsible for the observed light green color of the solution, mirroring the color of the hydrated crystals from which the solution is prepared.
In summary:
- Ferrous Sulphate Solution: Light green
- Hydrated Ferrous Sulphate Crystals (FeSO4.7H2O): Light green
- Anhydrous Ferrous Sulphate (FeSO4): White
This demonstrates that the light green color is associated with the hydrated form of ferrous sulphate, whether in crystalline form or dissolved in solution.
