Question

State your observations when ammonium hydroxide solution is added drop by drop and then in excess zinc sulfate solution.

Answer 1

In the above-given case when ammonium hydroxide solution to zinc sulfate solution, we could see a physical change, a color change which is due to the formation of the products.

Complete step-by-step answer: So in the question, it is asked what will be the observation if we add ammonium hydroxide solution to zinc sulfate solution first in a dropwise manner and then in excess quantity.
From the lower classes, we are discussing many chemical reactions in which we understand a reaction is proceeding or a reaction has happened by observing the physical change that has occurred in the system, either a color change, precipitate formation, evolution of gas, etc.
In the question, it is given first the ammonium hydroxide is added to copper sulfate and zinc sulfate solutions as drop by drop, with time reaction take place and a compound is formed, then the ammonia solution is added in excess then we could see another physical observation taking place in the system.
Let us discuss the reactions and observations associated with the chemical change.
When $N{{H}_{4}}OH$is added dropwise, $ZnS{{O}_{4}}$a white gelatinous precipitate is formed by the displacement reaction. The precipitate formed is zinc hydroxide.
$ZnS{{O}_{4}}+2N{{H}_{4}}OH\to \underset{\left( White\,gelatinous\,ppt \right)}{\mathop{Zn{{\left( OH \right)}_{2}}\downarrow +{{\left( N{{H}_{4}} \right)}_{2}}S{{O}_{4}}}}\,$
When ammonium hydroxide is added in excess to the reaction vessel then the precipitate dissolves and forms a complex which is colorless. So the observation is a change from white gelatinous precipitate to a colorless solution.
$Zn{{\left( OH \right)}_{2}}+{{\left( N{{H}_{4}} \right)}_{2}}S{{O}_{4}}+2N{{H}_{4}}OH\to \left[ Zn{{\left( N{{H}_{3}} \right)}_{4}} \right]S{{O}_{4}}+4{{H}_{2}}O$
The colorless solution is due to the formation of tetraamine zinc (II) sulfate.

Note: The color of zinc sulfate is white and it exists in a solid-state and it on dilution with water to form the zinc sulfate solution gives a colorless solution.