Which gas is soluble in water?

Answer: The following factors affect how soluble gas is in water:

1. Partial pressure – The partial pressure of a gas above a liquid directly relates to how soluble it is in the liquid.
2. Critical temperature – With an increased critical temperature, gas solubility is more excellent. Compared to H₂, CO2 is more soluble.
3. Gasses with ionization potential are more soluble in water. Because NH3 ionises in water to generate NH4+, it is more soluble than CO2.

NH3 is the most soluble gas in water because it forms a hydrogen bond with the liquid.