Question
Write the observation, and balanced equation for the following reaction:
Ammonium hydroxide is added first in a small quantity, and then in excess, to a solution of copper sulphate.

Answer

When ammonium hydroxide is added in small quantity to copper sulphate solution; it gives blue precipitate of $Cu ( OH )_2$
$
\underset{\text { Blue }}{ CuSO _4}+2 NH _4 OH \longrightarrow \underset{\text { Pale blue ppt. }}{ Cu ( OH )_2}+\left( NH _4\right)_2 SO _4
$
When ammonium hydroxide is added in excess, the blue precipitate dissolves giving deep blue solution of tetra amine copper sulphate.
$
\begin{aligned}
& Cu ( OH )_2+\left( NH _4\right)_2 SO _4+2 NH _4 OH \longrightarrow \quad\left[ Cu \left( NH _3\right)_4\right] SO _4 \\
& \text { In excess } \quad \text { Tetrammine copper(II) Sulphate (Deep blue solution) } \\
&
\end{aligned}
$

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