Arrange the following compounds in increasing order of solubility in water:

C₆H₅NH₂, (C₂H₅)₂NH, C₂H₅NH₂

The increasing order of solubility in water of the given compounds is as follows:

 C₆H₅NH₂ < (C₂H₅)₂NH < C₂H₅NH₂

The more extensive the hydrogen bonding, the higher is the solubility of the compound in water. C₂H₅NH₂ contains two H-atoms, whereas (C₂H₅)₂NH contains only one H-atom. Therefore, C₂H₅NH₂ is more soluble than (C₂H₅)₂NH. The solubility of C₆H₅NH₂ is least due to its high molecular mass.