Question

Salt and the acid used in the laboratory preparation of hydrogen chloride is:
A.Sodium chloride and sulphuric acid
B.Sodium chloride and water
C.Sodium chloride and hydrogen
D.Chlorine and hydrogen

Answer 1

Hydrogen chloride is a covalently bonded molecule which generally exists as a gas. When added in water it works as an acid forming a proton and a chloride ion. You must recall the preparation of hydrogen chloride in the laboratory in order to answer this question.

Complete answer:
Hydrogen chloride gas is produced in the laboratory by treating sodium chloride with sulphuric acid in a reaction vessel. The reaction occurring in the preparation can be given as:
$NaCl + {H_2}S{O_4} \to N{a_2}S{O_4} + HCl$

Thus, the correct answer is A.

Additional information: The hydrogen chloride produced on reaction of sodium chloride and sulphuric acid is put into another vessel containing sulphuric acid which dries the gas. The dry hydrogen chloride gas is then made to go to the vessel containing water through an extra empty vessel which accommodates for the back suction of water during the absorption of the dry hydrogen chloride gas. The pipe leading the dry gas into the vessel of water is attached to an inverted funnel which provides an enhanced surface area for absorption and hence minimizes back suction of water.
Direct absorption of hydrogen chloride gas in water is not feasible as direct absorption leads to the back suction of water. It is caused when the rate of absorption exceeds the rate of production of the hydrogen chloride gas. Thus, a low pressure is created in the flask which causes the water to be pulled into the reaction flask.

Note:
Most of the hydrogen chloride produced industrially is for the production of hydrochloric acid. At large scale, hydrogen chloride is produced by directly combining hydrogen gas and chlorine gas. The reaction is highly exothermic and a great amount of heat is produced. The gas produced is then absorbed into water forming pure hydrochloric acid.