Question

It has been observed that gaseous hydrogen chloride is a very poor conductor of electricity but a solution of hydrogen chloride gas in water is a good conductor of electricity. This is due to the fact that
A. Water is a good conductor of electricity.
B. Hydrogen chloride gas in water solution ionises.
C. A gas is non-conductor but a liquid conducts electricity.
D. Gas does not obey Ohm's law whereas solution does.

Answer 1

Hint: Ionic compounds are good conductors of electricity whereas covalent compounds are not. Here, hydrogen chloride in gaseous form is a strong covalent compound. But it may not exist in the same manner when dissolved in water.

Complete Step by Step Answer:
Hydrogen chloride, a hydride of chloride, is also known as hydrochloric acid. It is a strong acid used in many chemical synthesis.

Hydrogen chloride is formed due to the reaction of hydrogen atom and chlorine atom. Hydrogen atom contains only one electron in its valence shell and chlorine atom also contains one electron less from noble gas configuration in its valence shell so, hydrogen and chlorine atoms share their electrons and form a covalent bond between them.

Hydrogen chloride is a polar covalent compound so it ionises in water and exists as hydrogen ion and chloride ion which conducts electricity.
Thus the correct option is B.

Note: We have seen that hydrogen chloride is break down into ions when dissolved in water but hydrogen fluoride does not break down into ions. Due to presence of strong hydrogen bonding it remains undissolved in water.