Identification Of Chlorine | Laboratory Preparation Of Hydrochloric Acid | Industrial Preparation Of HCl


1. Identification Of Chlorine:

Chlorine gas is identified by the following tests.

1.1. Colors:

Note the colors of the unknown gas if it is greenish yellow color it is probably chlorine.

1.2. Damp Utmus Paper Test:

Drep a piece of dramp blue utmus paper into a gas jar of the unknown gas, if the litmus paper turns pink and then it becomes bleached, the gas is chlorine.

1.3. Starch Iodide Paper Test:

Drop a piece of damp starch iodide paper (paper aipped in a mixture of starch and a solution of potassium iodide) into a gas jar of the unknown gas if the paper turns blue then the gas is chlorine.

2. Laboratory Preparation Of Hydrochloric Acid:

Hydrogen chloride is usually prepared in the laboratory by action of concentrated sulphuric acid on common salt (Nacl).

2.1. Reaction:

2Nacl + H2So4 (conc) ---> Na2So4 + 2HCl

2.2. Procedure:

Common salt is taken in the bottom flask. A delivery tube bent twice at right angles and a thistle funnel are fitted into the flask through a cork, concentrated sulphuric acid is poured from the thistle funnel into the flask, until the salt and the end of the thistle funnel dip into the acid, the reaction, takes place at room temperature. The gas is collected in jars placed under the end of delivery rube by upward displacement of the air the gas is highly soluble in water, it dissolves in water to form hydrochloric acid.

3. Industrial Preparation Of Hcl:

Hydrogen chloride is manufactured industrially by the direct combination of hydrogen and chlorine gases obtained from the electrolysis of brine (refer to chlorine preparation).