Hydrogen chloride gas is prepared in the lab by the action of concentrated sulphuric acid on sodium chloride.

H2SO4 (aq)+NaCl(s)→NaHSO4 (aq)+HCL(g)

The gas is dried using concentrated sulphuric acid and collected by downward delivery.

Chemical Properties of HCL gas

It reacts with red hot iron to form iron II chloride

Fe(s)+2HCL(aq)→FeCl2 (s)+H2O(l)

Physical Properties of HCL gas

• It is very soluble in water.
• It has a strong pungent smell
• It is denser than air

Test for Chlorides, Bromides and Iodides

• Chlorides (Cl^-): When the salt solution is made, dilute nitric acid (HNO₃) is added, silver nitrate (AgNO₃) solution is added, and if the salt is a chloride white precipitate will be formed. The precipitate is soluble in dilute ammonia (NH₃).

Ag(aq++Cl(aq)-→AgCls White

• Bromide (Br^-): A solution of the salt is made. Dilute nitric acid (HNO₃) is added to the solution, followed by silver nitrate (AgNO₃) solution. A pale yellow precipitate indicates the presence of a bromide. It is soluble only in concentrated ammonia (NH₃).

Ag(aq)++Br(aq)-→AgBrs     Pale yellow

• Iodine (I^-): The salt solution is made. Dilute nitric acid (HNO₃) is added, followed by silver nitrate (AgNO₃) solution. A yellow precipitate which is insoluble in concentrated ammonia (NH₃) indicates the presence of Iodine.

Ag(aq)++I(aq)-→AgI(s)     Yellow

Why is Fluorine and Astatine not Studied in Secondary School?

19. Fluorine is too reactive.
19. Astatine is radioactive and cancerous.