When to a copper sulphate solution , excess of ammonium hydroxide added then

Options

A. No change is observed
B. Blue precipitate of copper hydroxide is obtained
C. A deep blue solution is obtained
D. Black precipitate of copper oxide is obtained

Answer

To solve the question regarding the reaction of copper sulfate solution with excess ammonium hydroxide, we can follow these steps:

### Step 1: Understand the Initial Reaction
When copper sulfate (CuSO₄) is added to ammonium hydroxide (NH₄OH), a reaction occurs that initially produces copper hydroxide (Cu(OH)₂) as a precipitate. The balanced equation for this reaction is:

\[ \text{CuSO}_4 + 2 \text{NH}_4\text{OH} \rightarrow \text{Cu(OH)}_2 \downarrow + \text{(NH}_4)_2\text{SO}_4 + 2 \text{H}_2\text{O} \]

### Step 2: Identify the Precipitate
The copper hydroxide formed is a blue precipitate. This is an important observation as it indicates that the reaction is taking place.

### Step 3: Excess Ammonium Hydroxide
When excess ammonium hydroxide is added, the blue precipitate of copper hydroxide does not remain as a solid. Instead, it reacts with the excess ammonium hydroxide to form a soluble complex.

### Step 4: Formation of the Complex
The copper hydroxide reacts with the ammonium ions from the excess ammonium hydroxide to form a deep blue solution of the complex ion tetraamminecopper(II) sulfate:

\[ \text{Cu(OH)}_2 + 4 \text{NH}_4\text{OH} \rightarrow [\text{Cu(NH}_3)_4]^{2+} + \text{SO}_4^{2-} + 4 \text{H}_2\text{O} \]

### Step 5: Conclusion
The final product is a deep blue solution of tetraamminecopper(II) sulfate, which confirms that the correct answer to the question is that a deep blue solution is obtained.

### Final Answer
The correct option is: **Third is a deep blue solution is obtained.**

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