Question

What is Blue Vitriol? Write about the effect of heat on it.

Answer 1

Crystalline copper sulphate is known as blue vitriol. It is an inorganic compound.Blue Vitriol is Pentahydrated Copper(ll) Sulphate. It occurs in nature in blue colour. That is why it is called blue vitriol. Its chemical formula is $CuS{O_4}.5{H_2}O$.

Complete step by step answer: When heated it loses the water of crystallisation. There are five water molecules present in blue vitriol. This leaves the molecule upon heating. Then the crystal is converted into grey powder which is known as anhydrous copper sulphate. It also loses its blue colour upon heating. The corresponding chemical reaction is,
$CuS{O_4}.5{H_2}O\xrightarrow{\Delta }CuS{O_4} + 5{H_2}O$
On heating at ${100^0}C$, it loses four water molecules of crystallisation giving monohydrated copper sulphate. When heated at ${230^0}C$, it loses the remaining one water molecule to give the grey powder of anhydrous copper sulphate. This can be converted again into blue by mixing with water. On strong heating it undergoes dissociation to form CuO and $S{O_3}$. The reaction is,
$CuS{O_4}\xrightarrow{{{{730}^0}C}}CuO + S{O_3}$

Additional information-
Copper sulfate has a variety of uses. Some of them are,
-Used as fungicide and herbicide
-It is a good analytical agent. Used in Fehling solution and Benedict’s solution for the test of reducing sugars.
-Used in organic synthesis.
-It is used as an antidote.
-An aqueous solution of copper sulphate is used as a resistive element in liquid resistors.
-Used as mordant in vegetable dyeing.

Note:
Copper sulphate is found with a number of crystallisation waters ranging from one to five. But most commonly seen form is pentahydrated copper(ll) sulphate