Nitric oxide (NO) is a colorless, odorless gas molecule produced in the body, serving as a signaling molecule that plays a crucial role in various physiological processes, including vasodilation and neurotransmission. Nitric Oxide is used to prepare nitric acid.
Laboratory Preparation of Nitric Oxide
The oxide is prepared in the laboratory by treating the metallic copper with a moderately concentrated nitric acid (1:1) at room temperature.
The reaction is given as :
3Cu + 8HNO3→ 3Cu(NO3)2 + 2NO + 4H2O
The gas is collected by downward displacement of water.
The apparatus used is Wolfe's apparatus.
The purification is done by absorbing the NO gas in freshly prepared ferrous sulphate solution.
Ferrous sulphate absorbs all the NO gas and forms Fe(H2O)5NO and the solution becomes brown.
On heating this solution pure Nitric Oxide is obtained.
Physical Properties of Nitric Oxide
NO is not a combustible gas. At high temperature around 1000°C it decomposes into N2
and O2.
2NO → N2 + O2 (at high temperature)
From the equation above we can see that once the decomposition starts 50% O2
gets evolved and this O2 supports combustion thus making the reaction more violent.
Chemical Properties of Nitric Oxide
1) NO acts as an oxidising agent, oxidising SO2 in presence of water to give H2SO4.
SO2 + 2NO + H2O → H2SO4 + N2O
2) NO acts as a reducing agent. It can reduce aqueous solution of I2 to HI
3I2 + 2NO + 4H2O → 2HNO3 + 6HI
3) With halogens, NO can form addition compounds as:
2NO + Cl2→ 2NOCl (NOCl is nitrosyl chloride)
It reacts in the same way with fluorine and bromine.
4) With ferrous sulphate, NO forms an addition compound as
FeSO4 + 5H2O + NO → [Fe(H2O)5NO]SO4
penta aqua nitrosyl iron (II) sulphate
This is the famous brown ring test used to identify the nitrate radical or the NO radical.
