Nitrous oxide : It is also called Laughing Gas.
Method of preparation:
1) By the reaction of zinc or iron on cold and dilute HNO3 : Nitrous oxide is formed.
4 Zn + 10 HNO3 ——–> 4 Zn(NO3)2 + N2O + 5H2O
4 Fe + 10 HNO3 ——–> 4 Fe(NO3)2 (ferrous nitrate) + N2O + 5 H2O
2) By reduction of HNO3 with SnCl2 and HCl : Nitrous oxide is formed.
4 SnCl2 (stannous chloride) + 8 HCl + 2 HNO3 ——–> N2O + 4 SnCl4 (stannic chloride) + 5 H2O
A mixture of ammonium sulphate and sodium nitrate on heating below 25OoC gives nitrous oxide.
source : etc.usf.edu
(NH4)2SO4 + 2 NaNO3 ——-> Na2SO4 + 2NH4NO3
NH4NO3 ——-> 2H2O + N2O
N2O may be obtained by direct heating of Ammonium nitrate below 250 oC but reaction is very fast and explosion takes place.
N2O is collected over hot water because it is soluble in cold water.
Nitrous oxide contains impurities of Cl2, HNO3, NO (nitric oxide), NH3 and water vapour. To remove these impurities it is passed to the solution containing NaOH, FeSO4 and concentrated H2SO4.
Sodium hydroxide removes the impurities of chlorine & nitric acid.
Cl2 +NaOH ——–> NaCl + NaClO +H2O
HNO3 +NaOH ——> NaNO3 + H2O
Ferrous sulphate removes the impurity of nitric oxide
FeSO4 + NO ——-> FeSO4.NO (Nitroso ferrous sulphate)
Sulphuric acid removes the impurities of ammonia & water vapour.
2NH3 + H2SO4 —–> (NH4)2SO4
Concentrated H2SO4 is dehydrating agent it also absorbs water vapours.
- Nitrous oxide is colorless sweet smelling gas.
- Laughing gas is soluble in cold water but insoluble in hot water.
- If N2O is inhaled for a long time it produces insensibility and may cause even death.
- It is a neutral oxide and has no effect on litmus paper.
a) Decomposition: It decomposition starts at 5200C & completely decomposed at 9000C
2N2O ——> 2N2 + O2 (at electric spark)
At high temp.
2N2O —–> 2NO + N2
b)Reaction with Sodamide:
N2O + NaNH2 (Sodamide) ——–>NaN3 (Sodium azide) + H2O
N2O and O2(mixture) is used as anesthetic agent in surgical operation.
Structure of Nitrous oxide :
source : commons.wikimedia.org