Gas solubilities.........?

Question

Why there are much higher solubilities of ammonia and hydrogen chloride compared to that of carbon dioxide?What the reason?

Answer 1

Ammonia (NH3) is capable of forming Hydrogen bonds or proton bridges with water molecules. This is because of the fact that in NH3, the more electronegative N atom gains a partial negative charge & in H2O the H atoms gains a partial positive charge, that is why, they tend to get attracted to each other ,they are not bonded but there exists strong electrostatic force of attraction between them, this is called Hydrogen bonding & due to the development of this type of so called "bond", ammonia is highly soluble in water.

The hydrogen chloride molecule HCl is a simple diatomic molecule consisting of a hydrogen atom H and a chlorine atom Cl connected with a covalent single bond. Since the chlorine atom is much more electronegative than the hydrogen atom, the covalent bond between the atoms is quite polar. Consequently the molecule has a large dipole moment with a negative partial charge δ- at the chlorine atom and a positive partial charge δ+ at the hydrogen atom. In part due to its high polarity, HCl is very soluble in water (and in other polar solvents). Thsi is called dipole-dipole attraction. Its weaker than H-bonding in NH3 though electronegativity of N = 3.04 & of Cl = 3.16 because there are 3 H atoms in NH3 to supply electrons to the N-atom . so HCl is soluble in water but in smaller extent.

CO2 is neither a polar compound nor is capable of forming H-bonds with water molecules so it is least soluble in water among the three.

Answer 2

Ammonia is very soluble because it can hydrogen-bond with water. HCl is very soluble because it reacts with it to form H+ and separate Cl- ions. CO2 is totally non-polar, which makes it pretty insoluble.