Question

What do you see when pentahydrated copper sulfate crystals are heated? Give a reaction too.

Answer 1

Hint: Pentahydrated copper sulfate is crystals having blue color. Copper sulfate is a powdered form which is white. In pentahydrated copper sulfate crystals, there are 5 molecules of water and when they are heated the water evaporates.

Complete step by step answer:
Pentahydrate copper sulfate is an inorganic compound having formula $CuS{{O}_{4}}.5{{H}_{2}}O$ in which there are five molecules of water. These are in crystal form and have blue color due to which it is known as several names like bluestone, blue vitriol, the vitriol of copper, and Roman vitriol.
The molecular mass of pentahydrate copper sulfate is $249.685\text{ g/mol}$.
The melting point of pentahydrate copper sulfate is ${{110}^{\circ }}C$ which means the at this temperature the pentahydrate copper sulfate will lose its 5 water molecule and convert into anhydrous copper sulfate.
So, we can say that when pentahydrate copper sulfate is heated it loses its water molecules and gets converted into anhydrous copper sulfate. Also on heating, the blue crystal of pentahydrate copper sulfate gets converted into grey-white powder copper sulfate. The reaction is given below:
$CuS{{O}_{2}}.5{{H}_{2}}O\to CuS{{O}_{4}}+5{{H}_{2}}O$
This reaction involves both chemical and physical change as the reactant is converted into the product makes it a chemical change, and the color changes from blue to white as well as the crystal form changes to powder form, making it a physical change.

Note: We can get a specified number of water molecules by heating the pentahydrate copper sulfate at different temperatures. As 2 water molecules evaporate at ${{60}^{\circ }}C$, two more evaporate at ${{105}^{\circ }}C$.