Chapter 9, Problem 119QRT

(a)

Interpretation Introduction

Interpretation:

A plot of the boiling point in kelvins versus the number of hydrogen atoms present in $Ne,HF,H_{2}O,N{H}_{3}andC{H}_4$ has to be drawn.  Any trend that can be observed in terms of intermolecular forces has to be explained.

Concept Introduction:

Hydrogen bonding:

Hydrogen bonding is a special form of dipole-dipole interaction.  When a hydrogen atom is bonded to a small electronegative atom (like $N,OandF$), then the electronegative atom pulls electron density away from the hydrogen atom.  This results a partial positive charge on the hydrogen atom and a partial negative charge on the electronegative atom.  The hydrogen atom on one molecule will be attracted to the electronegative atom on another molecule. Like this hydrogen bonding takes place.  It is quite stronger than other intermolecular forces like dipole-dipole interactions and London forces.

London forces:

London(dispersion) forces happen because sometimes, when adjacent molecules line up so that they form temporary dipoles, there is a weak force of attraction between the end of one molecule where more of the electrons are accumulating at the moment and the end of a second molecule where the electrons are not staying at the moment.

(b)

Interpretation Introduction

Interpretation:

A plot of the molar vaporization enthalpy versus the number of hydrogen atoms present in $Ne,HF,H_{2}O,N{H}_{3}andC{H}_4$ has to be drawn.  Any trend that can be observed in terms of intermolecular forces has to be explained.

Concept Introduction:

Refer to part (a).