Hydrogen Chloride is a Diatomic Molecule which consists of two atoms. The atoms in diatomic molecules may be similar (e.g. Oxygen Nitrogen Hydrogen etc.) or they may be dissimilar (e.g. Carbon Monoxide, Hydrogen Chloride, etc.).
(i) as a solution or (ii) as a fuming gas.:
(i) as a solution of Hydrogen Chloride in water, where the molecule is dissociated in solution into its ions.
HCl ==> H(+) + Cl(-)(ii) as a colourless fuming gas. The polar covalent gas Hydrogen Chloride is very soluble in Water. In aqueous solution, the molecule exists in ionic form, as the positively charged Hydrogen Ion, H(+), and the negatively charged Chloride Ion, Cl(-).
HCl + ==> H(+) + Cl(-) Hydrogen Hydrogen Chloride Chloride Ion IonIt should be noted that the Hydrogen Ion, H(+), is stabilised by hydration in aqueous solution, as the Hydronium Ion, H3O(+).
H(+) + H2O ==> H3O(+) Hydrogen Hydronium Ion Ion
Hydrogen Chloride gas is very soluble in water, and a solution of the gas forms Hydrochloric
When 1 kgm. of water is saturated with the gas at 15 degC It increases in weight to 1.75 kgm., and the relative density is 1.231.
It contains about 43 per cent of HCl; the commercial acid contains about 39 per cent and its relative density is 1.20.
Many Metallic Chlorides liberate Hydrogen Chloride gas, HCl, when warmed with concentrated Sulphuric Acid, H2SO4.
It is prepared industrially by the combustion of Hydrogen, H2, in Chlorine, Cl2.
H2 + Cl2 ==> 2 HClHydrogen Chloride may be prepared in the laboratory by heating Concentrated Sulphuric Acid, with Sodium Chloride.
NaCl + H2SO4 ==> NaHSO4 + HClThe Chlorides of Non-Metals (e.g. Phosphorus Trichloride, PCl3) are covalent compounds.
PCl3 + 3 H2O ==> H3PO3 + 3 HClPhosphorus Pentachloride, is hydrolysed by hot Water, to give Orthophosphorus Acid, (i.e. Phosphoric(V)Acid) and Hydrogen Chloride.
PCl5 + 4 H2O ==> H3PO4 + 5 HClPhosphorus Pentachloride, is also hydrolysed by cold Water, to give Phosphorus Oxychloride.
PCl5 + H2O ==> POCl3 + 2 HClA mixture of Chlorine, Cl2, and Hydrogen, H2, explodes when exposed to sunlight to give Hydrogen Chloride, HCl. In the dark, no reaction occurs, so activation of the reaction by light energy is required.
Cl2 + H2 ==> 2 HClChlorine, removes Hydrogen, from the hydrides of non-metals, forming Hydrogen Chloride, and leaving the non-metal element.
Cl2 + H2S ==> 2 HCl + SWhen Chlorine Water, (i.e. a solution of Chlorine gas, in Water) in a flask inverted in a basin of the same liquid is exposed to bright sunlight, the Chlorine, is decomposed and a solution of Hypochlorous Acid, remains.
H2O + Cl2 ==> HCl + HClOThe Hypochlorous Acid, is not very stable and the solution readily decomcomposes, especially when exposed to sunlight, yielding Oxygen,
2 HClO ==> 2 HCl + O2Chlorine, is soluble in water (which solution is called Chlorine Water) and this loses its yellow colour on standing in sunlight, due to the formation of a mixture of Hypochlorous Acid, and Hydrochloric Acid.
Cl2 + H2O ==> HOCl + HCl
Ferrous Chloride, is formed by reacting Iron, or Ferrous Oxide, with dilute Hydrochloric Acid.
FeO + 2 HCl ==> FeCl2 + H2OEthyne, reacts with Hydrogen Chloride, very slowly.
HCCH + HCl ==> H2C=CHCl + HCl ==> CH3CHCl2Ethanol, reacts with Hydrogen Chloride, to form Ethyl Chloride, (i.e. chloroethane) and Water. A dehydrating agent (e.g. Zinc Chloride) is used.
ZnCl2 C2H5OH + HCl =====> C2H5Cl + H2O Ethanol Ethyl ChlorideSubstitution of Methanol with Hydrogen Chloride
Methanol, reacts with Hydrogen Chloride, to form Methyl Chloride, (i.e. chloromethane) and Water. A dehydrating agent (e.g. Zinc Chloride,) is used.
ZnCl2 CH3OH + HCl ==> CH3Cl + H2O Ethanol Methyl ChlorideCalcium Chloride, is prepared by dissolving limestone chips (i.e. a naturally occurring form of Calcium Carbonate) or marble chips (i.e. also a naturally occurring form of Calcium Carbonate) in Hydrochloric Acid.
Chlorides are the salts of Hydrochloric Acid, and they are also produced in the direct reaction between their constituent elements.
In the laboratory, a mixture of Cuprous Chloride, and Hydrochloric Acid, is used for converting Benzene Diazonium Chloride, to Chlorobenzene, in the Sandmeyer Reaction.
MnO2 + 4 HCl ==> MnCl2 + 2 H2O + Cl2The gas is bubbled through water to remove any traces of hydrochloric gas that may be present and then it is dried by bubbling it through concentrated sulphuric acid. Chlorine, may also be prepared by dropping cold concentrated Hydrochloric Acid, on Potassium Permanganate.
2KMnO4 + 16HCl ==> 2MnCl2 + 2KCl + 8H2O + 5Cl2The gas is bubbled through Water, to remove any traces of Hydrochloric Acid gas, that may be present and then it is dried by bubbling it through concentrated Sulphuric Acid.
Ionic Chlorides (i.e. salt-like chlorides) are prepared by the action of Hydrochloric Acid,
(a) on a Metal, (b) on a Metal Oxide, (c) on a Metal Hydroxide, or (d) on a Metal Carbonate.For example, Calcium Carbonate, reacts with Hydrochloric Acid, to form Calcium Chloride.
CaCO3 + 2 HCl ==> CaCl2 + H2O + CO2