Question

Consider the following data concerning the solubility of two gaseous compounds, ammonia and hydrogen chloride, at various temperatures:

I) Molar solubility of gaseous Ammonia and Hydrogen Chloride as a function of temperature.

II) The molar solubility of ammonia gas is significantly greater than that of hydrogen chloride at $0^{\circ }C$, but its solubility drops off dramatically with increasing temperature.

III) By comparison, raising the temperature causes the molar solubility of hydrogen chloride to decrease at first, but as the temperature gets even higher, the molar solubility of $HCl$ begins to increase.

Which of the following best explains the difference in solubilities at $0^{\circ }C$?

• A. Ammonia molecules are smaller than hydrogen chloride molecules, so fit into the spaces between water molecules more readily.
• B. Ammonia is able to hydrogen bond to water, but hydrogen chloride is not.
• C. Ammonia ionizes less in water, and so is able to dissolve better.
• D. Hydrogen chloride gas is less dense than ammonia gas, so it tends to escape from solution more readily.

Answer 1

Answer: (B)

Ammonia is able to hydrogen bond to water, but hydrogen chloride is not.

Liquid solution is formed when solvent is a liquid, ammonia molecules is able to form hydrogen bond with water molecules, so on increasing temperature intermolecular interactions between particles decreases and hydrogen bond breaks, so its solubility decreases dramatically on increasing temperature.

Hence, option (B) explains the situation best.