Consider the following data concerning the solubility of two gaseous compounds, ammonia and hydrogen chloride, at various temperatures.
Molar Solubility of Gaseous Ammonia and Hydrogen Chloride as a Function of Temperature
|0||52.9 M||22.5 M|
|20||14.8 M||12.3 M|
|60||3.5 M||15.3 M|
The molar solubility of ammonia gas is significantly greater than that of hydrogen chloride at 0ºC, but its solubility drops off dramatically with increasing temperature.
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 is the BEST explanation for the fact that hydrogen chloride's molar solubility remains high, and even increases between 20ºC and 60ºC, while the molar solubility of ammonia drops steadily?