Exercise 2 | Liquids and Solids

Arrange the following compounds in order of increasing boiling point:

MgO, NH3, PH3 and KCl

MgO: ionic compound ⇒ Mg2+ and O2- = divalent ion ⇒ strong attraction

KCl: ionic compound ⇒ K+ and Cl- = monovalent ion ⇒ strong attraction but less than MgO

NH3: polar molecule + hydrogen bonding

PH3: polar molecule but no hydrogen bonding

 

Boiling point: PH3 < NH3 < KCl < MgO