In what way it can be proved that PH_3 is basic in nature.
PH_3 reacts with acids like HI to form phosphonium iodide, PH_4I.
PH _3+ HI \longrightarrow PH _4 I
Phosphonium iodide
This shows that PH_3 is basic in nature. This basic nature of PH_3 is due to the presence of lone pair on phosphorus atom and therefore, it acts as a Lewis base.