Ammonium salts and ammonia identification experiments, reactions and characteristics are discussed in this tutorial. Some ammonium compounds release ammonia gas when those compounds are heated. Ammonia is a toxic gas. But it has so many industrial uses such as manufacturing nitric acid.
Add aqueous strong base to any ammonium salt and heat the mixture. Then ammonia gas (NH3) is released.
H atoms in NH4+ molecule are positively charged because electronegativity of N atom is higher than H. In OH- ion, electron density around O atom is high. So that electrons attacks H atoms (positively charged) of NH4+ molecule. As a result, one N-H bond breaks and gives NH3 and H2O as products.
Nitrous oxide(N2O) and water are formed when NH4NO3 is heated.
Nitrogen(N2) and water are formed when NH4NO3 is heated.
NH4OH decomposes to NH3(g) and H2O(g).
When ammonium sulfate( (NH4(2SO2) is heated, it decomposes to NH3(g) and H2SO4(g).
NH3(g) and H3PO4(g) are produced by the decomposition of (NH4)3PO4.
When ammonium carbonate( (NH4)2CO3 ) is heated, it decomposes to ammonia, carbon dioxide and water. Ammonium carbonate is a solid, but all products are in gaseous phase.
Heating a mixture of ammonium chloride and potassium dichromate also gives nitrogen(N2) , chromium oxide ( Cr2O3 ) and water as products.
When ammonium perchlorate(NH4ClO4) is heated above 2000C, it decomposes to nitrogen(N2), chlorine(Cl2), oxygen(O2) and water.
Now we discuss decomposition halides ( Cl- , Br- , I- ) of NH4+ ions.
Decomposition of NH4I give NH3 and HI. But HI is not stable to heat. Therefore when furthermore heating HI decomposes to H2 and I2 gases. I2 is a purple gas.
Decomposition of NH4Br give NH3 and HBr. But HBr is not stable to heat. Therefore when furthermore heating HBr decomposes to H2 and Br2 gases. Br2 is a brown gas.
Decomposition of NH4Cl give NH3 and HCl. HCl is stable to heat. Therefore it does not decompose furthermore.
Ammonia has a lot of reactions due to its different reaction types as an acid, as a base, as a reducing agent, reactions. Ammonia is a toxic gas. When ammonia gas dissolve in water, it forms aqueous ammonium hydroxide which is basic. Ammonia has number of industrial uses such as manufacturing nitric acid.
Nitride ions(N3-) ion are exceedingly
strong bases and react with almost
any proton donor to produce ammonia(NH3).
Magnesium nitride (Mg3N2) react with water and produce ammonia and magnesium hydroxide.
Sodium nitride(Na3N) react with water and produce ammonia and sodium hydroxide.
Devards's alloy is a mixture of metals 50% Cu , 45% Al , 5% Zn. This Devards's alloy , nitrate(NO3-) and strong alkali react and nitrate is reduced to NH3.
Ammonia can behave as a acid, a base, an oxidizing reagent, a reducing agent. Therefore ammonia has wide variety of reactions.
By the reaction of
alkali metals, hydrogen(H2) gas is liberated and metal amine are formed.
Therefore we can say ammonia can act as an acid. In this reaction Na is oxidized into Na+ ion. Therefore ammonia
behaves as an oxidizing reagent too.
2Na + 2NH3 → 2NaNH2 + H2
2K + 2NH3 → 2KNH2 + H2
NaH is a strong base. It reacts with NH3 to give sodamide (Sodium amide, NaNH2) and H2.
Ammonia dissolves very well in water. But ammonia partially hydrolysis and give OH-. Otherwise, we can say dissociation of ammonia in the water is weak. However aqueous ammonia solution is basic due to release of OH- ion by the reaction of ammonia and water. Ammonia is a weak base.
In some reactions, NH3 is oxidized. Oxidation number of N in ammonia is -3. Therefore NH3 can be oxidized to N2( Oxidation number of N = 0), NO( Oxidation number of N= +2).
In NH3 combustion with O2 without catalyst, it gives N2(g) and H2O(g).
In NH3 combustion with O2 with Cu or Pt/Rh catalyst, it gives NO(g) and H2O(g). Cu is used in the laboratory as the catalyst. But industrially Pt/Rh is used as catalyst. This reaction is used in industrial manufacturing of nitric acid. NO is easily oxidized to NO2 in the air.
Heating ammonia and copper oxide ( CuO ) will give Cu and N2. CuO is brown and Cu is red brown.
CuO is reduced Cu
NH3 is oxidized to N2.
Silver oxide ( Ag2O ) and ammonia can react in two ways.
When Ag2O is heated O2(g) is emitted. That releasing O2 can react with NH3 to give N2.
NH3(aq) and Ag2O react to give [Ag(NH3)2] colourless coordination complex.
There are two states of this reaction.
In the first step, NH3 and Cl2 react to give N2 and HCl. Produced HCl again reacts with remaining NH3 producing NH4Cl, a solid white fog.
Aqueous ammonia solution partially dissociates to give OH- in the water. Some d block cations forms precipitates with OH- ions.
NH3 has a one lone pair. Therefore NH3 can behave as a ligands to form coordination complexes.
First, 3d metal ions which have d7, d8, d9, d10 forms precipitates with NH3(aq). But adding more NH3(aq), those precipitates dissolve to form coordination complexes.
Both compounds have ammonium ion.
Add both compounds to aqueous barium chloride solution.
One compound forms a white precipitate. It is barium carbonate. That is related to the ammonium carbonate.
Ammonium salt reacts with alkali and release ammonia gas. As alkalis, NaOH, KOH, Ba(OH)2can be used.
NH4Cl + NaOH → NH3 + NaCl + H2O
Ammonium dichromate gives a green colour Cr2O3 when heating.