A blue colouration is not obtained when: a)ammonium hydroxide dissolve...
Explanation:
When copper sulphate solution reacts with K4[Fe(CN)6], a blue coloration is not obtained. This can be explained by the following points:
1. Formation of Precipitate:
When copper sulphate solution reacts with K4[Fe(CN)6], a double displacement reaction occurs. The potassium ions (K+) from K4[Fe(CN)6] react with the sulphate ions (SO4^2-) from copper sulphate (CuSO4) to form potassium sulphate (K2SO4). Similarly, the copper ions (Cu^2+) from copper sulphate react with the ferrocyanide ions (Fe(CN)6^-4) from K4[Fe(CN)6] to form a complex compound called copper ferrocyanide (Cu2[Fe(CN)6]), which is insoluble in water.
2. Insolubility of Copper Ferrocyanide:
Copper ferrocyanide is a blue precipitate that is formed during the reaction. Since it is insoluble in water, it does not dissolve and remains as a solid in the solution. This is why a blue coloration is not obtained.
3. Absence of Cu^2+ Ions:
The blue color in copper sulphate solution is due to the presence of Cu^2+ ions. However, during the reaction with K4[Fe(CN)6], the Cu^2+ ions are consumed in the formation of copper ferrocyanide. As a result, there are no free Cu^2+ ions available to impart the blue color to the solution.
4. Formation of White Precipitate:
Instead of the blue color, a white precipitate of copper ferrocyanide is formed. This white precipitate may give the impression of a colorless solution, but it is actually the result of the reaction between copper sulphate and K4[Fe(CN)6].
Therefore, when copper sulphate solution reacts with K4[Fe(CN)6], a blue coloration is not obtained due to the formation of insoluble copper ferrocyanide.