Laboratory Preparation of Hydrogen Chloride Gas

Vocabulary and chemical principles regarding the laboratory preparation, collection, and identification of Hydrogen Chloride gas based on the reaction of sodium chloride and sulphuric acid.

Sodium chloride [$NaCl$]

A metallic chloride, also known as rock salt, used as a reactant in the laboratory preparation of hydrogen chloride gas.

Concentrated sulphuric acid [$H_2SO_4$]

The acid used to react with sodium chloride and also functions as a drying agent in the washer bottle to absorb moisture.

Sodium bisulphate [$NaHSO_4$]

A product formed when sodium chloride and concentrated sulphuric acid are heated at a temperature below $200^\text{o}C$.

Reaction Equation ($< 200^\text{o}C$)

$$NaCl + H_2SO_4 \rightarrow NaHSO_4 + HCl[g]$$

Reaction Equation ($> 200^\text{o}C$)

$$2NaCl + H_2SO_4 \rightarrow Na_2SO_4 + 2HCl[g]$$

Drying of $HCl$ gas

The process of passing the gas through a washer bottle containing concentrated $H_2SO_4$ to absorb moisture.

Upward displacement of air

The method used to collect dry hydrogen chloride gas because it is heavier than air and highly soluble in water.

Identification of $HCl$ gas

A glass rod dipped in ammonia solution [$NH_3$] is brought near the gas jar; dense white fumes of ammonium chloride [$NH_4Cl$] indicate the presence of the gas.

Ammonium chloride [$NH_4Cl$]

The substance formed by the reaction $NH_3 + HCl \rightarrow NH_4Cl$, appearing as dense white fumes during the identification test.

Thistle funnel precaution

The lower end must dip below the acid in the flask to prevent the generated $HCl$ gas from escaping.

Reaction Mixture Heating

The reactants are initially heated very slowly to control the evolution of $HCl$ gas.