The correct answer is (3) Green.
Mohr's salt, scientifically known as ferrous ammonium sulphate, is a coordination compound with the chemical formula \([Fe(NH_4)_2(SO_4)_2 \cdot 6H_2O]\). It is a hydrated double salt containing iron, ammonium, and sulfate ions. The complex is commonly used in titration experiments, particularly for determining the concentration of permanganate ions (MnO₄⁻) in a solution.
Let's break down the composition and color of Mohr's salt:
1. Composition:
- The chemical formula \([Fe(NH_4)_2(SO_4)_2 \cdot 6H_2O]\) indicates that the complex consists of iron (Fe), ammonium (\(NH_4^+\)), sulfate (\(SO_4^{2-}\)), and water (\(H_2O\)) molecules.
- The ammonium ions and sulfate ions form coordination complexes with the iron ion in a specific arrangement.
2. Color:
- Mohr's salt is typically pale green in color. The green color is associated with the specific arrangement of ligands (ammonium and sulphate ions) around the iron ion in the complex.
- The absorption of certain wavelengths of light by the complex gives rise to its characteristic color.
3. Use in Titration:
- Mohr's salt is commonly used as a primary standard in titration experiments, particularly for titrating solutions containing permanganate ions (\(MnO_4^-\)).
- The reaction involves the oxidation of ferrous ions (\(Fe^{2+}\)) in Mohr's salt to ferric ions (\(Fe^{3+}\)) by permanganate ions (\(MnO_4^-\)).
- The endpoint of the titration is determined by a color change from pale pink (due to the permanganate ion) to a faint straw color, indicating the complete reaction.
Overall, Mohr's salt is a versatile compound in analytical chemistry, known for its distinctive pale green color and its role as a reliable primary standard in titration procedures. |
