Question

The copper sulphate solution during crystallization is filtered to:
A.separate copper
B. form crystals
C. separate impurities
D. all of the above

Answer 1

Hint:
Copper sulfate is a well-known inorganic compound also known as copper sulfate pentahydrate( $CuSO{}_4.5H{}_2O$). Basically, it has a blue colour. This blue color is for the water molecules attached to its crystal. The dehydrated copper sulfate is grey in colour.

Complete step by step answer:
The copper sulfate is also known as blue vitriol, due to its blue colour. The formula of copper sulfate is \[{\text{CuS}}{{\text{O}}_{\text{4}}}\]. This inorganic compound can be made by an electrolysis process. In this process sulfuric acid is used in solution and copper as electrodes. Impure copper is used as anode and pure copper is used as cathode. In this process copper from anode gets oxidized and comes to the solution. The copper ion from the solution get reduced in cathode and formed metallic pure copper.
The anode and cathode reactions are,
Anode :
\[{\text{Cu}} \to \,{\text{C}}{{\text{u}}^{{\text{ + 2}}}}{\text{ + 2}}{{\text{e}}^{\text{ - }}}{\text{(Oxidation)}}\]
Cathode:
\[\,{\text{C}}{{\text{u}}^{{\text{ + 2}}}}{\text{ + 2}}{{\text{e}}^{\text{ - }}} \to {\text{Cu (reduction)}}\]
 The copper sulfate pentahydrate is crystallized in water with addition of a small amount of sulfuric acid to stop the hydrolysis of copper sulfate. Then the solution is filtered to eliminate insoluble impurities from the copper sulfate. After filtration the solution is heated up to \[{\text{7}}{{\text{0}}^{\text{0}}}{\text{C}}\] temperature to reduce the volume. After the heating when the crystallization point is achieved, it is cooled.
So, the filtration of copper sulfate is to separate impurities.

The correct option is C.

Note:
Remember that during the crystallization process a small amount of sulfuric acid to stop the hydrolysis of copper sulfate. Then the solution is filtered to eliminate insoluble impurities from the copper sulfate. The copper sulfate is also known as blue vitriol, it can be made by electrolysis process.