Question

What is the Colour of Freshly prepared $ FeS{O_4} $ solution $ ? $

Answer 1

Hint: First we have to know that ferrous sulphate is an iron salt popularly known as green vitriol. $ FeS{O_4} $ is the chemical formula of iron(II) sulphate or ferrous sulphate. Ferrous fumarate, ferrous gluconate, and ferrous sulphate are generic names for oral iron. Ferrous sulphate is the best and cheapest iron supplement.

Complete answer:
When $ FeS{O_4} $ on exposure to the atmosphere, it is readily oxidized to ferric sulphate and does not support the formation of the brown ring. So, a freshly prepared $ FeS{O_4} $ is used to test nitrogen.
If $ FeS{O_4} $ is stored or it is the old one then it reacts with atmospheric oxygen and gets oxidized to form a corrosive brown-yellow coating of basic ferric sulphate, which is an adduct of ferric oxide and ferric sulphate. So, a freshly prepared ferrous sulphate is used in the brown ring test.
On keeping aqueous $ FeS{O_4} $ solution, it undergoes hydrolysis to form basic ferric sulphate. Its chemical reaction as follows
 $ 4FeS{O_4} + 2{H_2}O + {O_2} \to 4Fe\left( {OH} \right)S{O_4} $ .
The pale-yellow colour of $ F{e^{ + 3}} $ ions Interferes with the light green colour usually obtained in Lassaigne's test. So, a freshly prepared saturated solution of ferrous sulphate used in the Lassaigne's test for nitrogen.
Hence the freshly prepared $ FeSO_4 $ solution is blue-green in colour.

Note:
Note that Ferrous sulphate is a medicine used to treat and prevent iron deficiency anaemia. Iron helps the body to make healthy red blood cells, which carry oxygen around the body. $ FeC{l_3} $ is the chemical formula of iron(III) chloride or ferric chloride. The colour of a ferric chloride solution is yellow.