Ranking of given compounds in order of decreasing boiling point : KF > Formaldehyde > Carbon tertrafluoride
Explanation:
KF is an ionic compound. Hence ionic force is between KF molecules.
Formaldehyde is a polar compound due to presence of polar carbonyl group. Hence dipole-dipole force is present between formaldehyde molecules.
Carbon tetrafluoride is a non-polar molecule due to it's symmetrical structure. hence only van der waal force exists between carbon tetrafluoride molecules.
Order of intermolecular force (decreasing order): Ionic force > dipole-dipole force > van der waal force
So ranking of given compounds in order of decreasing boiling point : KF > Formaldehyde > Carbon tertrafluoride
