Which of the following is the correct order of increasing enthalpy of vaporisation?

Options

A. `NH_(3)gtPH_(3)gtAsH_(3)`
B. `AsH_(3)gtPH_(3)gtNH_(3)`
C. `PH_(3)gtAsH_(3)gtNH_(3)`
D. `NH_(3)gtAsH_(3)gtPH_(3)`

Answer

D

Explanation

Enthalpy of vapourisation increases down th group due to increase in van der waal's forces (due to increase in size). But ammonia forms H-bonds, has high boiling point and high enthalpy of vaporisation. Hence, the order is `NH_(3) gt AsH_(3) gt PH_(3)`