3. • .
HYDROGEN CHLORIDE –
• The compound hydrogen chloride has the chemical
formula HCI and as such is a hydrogen halide.
• Hydrogen chloride is a diatomic molecule, consisting of
a hydrogen atom H and a chlorine atom Cl connected
by a polar covalent bond.
• The chlorine atom is much more electronegative
• than the hydrogen atom, which makes this bond polar.
• Consequently, the molecule has a large dipole moment
with a negative partial charge (δ−) at the chlorine atom
and a positive partial charge (δ+) at the hydrogen atom.
4. PREPARATION OF HYDROGEN CHLORIDE -
Hydrogen Chloride is produced in the laboratory by treating sodium
chloride with concentrated sulphuric acid. Then, this mixture is heated up
to 420K.
NaCl + H2SO4 → NaHSO4 + HCl
Sodium bisulphate is obtained as a by-product which is insoluble.
Therefore, it is further mixed with more sodium chloride. This mixture has
to be further warmed to a higher temperature of around 823K. It gives
dissolvable sodium sulfate and HCl gas.
NaHSO4 + NaCl → Na2SO4 + HCl
This HCl is dried by treating it with concentrated sulphuric acid.
420K
823K
5. PROPERTIES OF HYDROGEN CHLORIDE =
1. Hydrogen Chloride is a vapid gas.
2. It has a very sharp and pungent odour.
3. Boiling point of hydrogen chloride is 189K.
4. Freezing point of hydrogen chloride is 159K.
5. It is extremely soluble in water. An aqueous solution of Hydrogen
Chloride is known as the hydrochloric acid.
6. HCI decomposes salts of weaker acids.
7. It reacts with NH3 and gives white fumes of NH4Cl.
NH3 + HCL NH4CL
8. Hydrochloric acid has a higher dissociation constant and is, therefore, a
strong acid.
9. Noble metals react with a mixture of nitric acid and hydrochloric acid in
the proportion of 1:3. This arrangement what we call Aqua Regia.
10. Gaseous hydrogen chloride reacts with active metals and their oxides,
hydroxides, and carbonates to produce chlorides
6. USES OF HYDROGEN CHLORIDE -
1. HCl is used in the preparation of chlorine, aqua regia, and other
chlorides.
2. It is used as a solvent to dissolve noble gases.
3. It acts as a reagent in laboratories.
4. It is used for extracting glue from bones and purified bone
black.
5. It is also a common ingredient in the fabrication of glucose from
corn starch.
6. Saturated arrangement of zinc chloride in dilute hydrochloric
acid is used in removing the contaminations on a metal surface
prior to welding or electroplating.
7. SOME IMPORTANT REACTION -
• Reaction with Sodium Carbonate:
Na2CO3 + 2HCl → 2NaCl + CO2↑ + H2O
• Reaction with Sodium Bicarbonate:
NaHCO3 + HCl → NaCl + CO2↑ + H2O
• Reaction with Sodium Sulphate:
Na2SO3 + 2HCl → 2NaCl + SO2↑ + H2O
