Question

On the basis of molecular structure and bond polarity, which of the following compounds is most likely to have the greatest solubility in water and why?
a)CH4
b)CCL4
c)NH3
d)PH3

Answer 1

Answer:

$\boxed{\text{c) NH _{3} ; hydrogen bonding}}$

Explanation:

For each of these molecules, you must determine their VSEPR structure and then identify the strongest intermolecular forces.

Remember that water is a highly polar molecule.

a) CH₄

  Electron geometry: tetrahedral

Molecular geometry: tetrahedral

          Bond polarity: C-H bond nonpolar

  Molecular polarity: nonpolar

        Strongest IMF: London dispersion forces

 Solubility in water: low

A nonpolar molecule is insoluble in a polar solvent.

b) CCl₄

  Electron geometry: tetrahedral

Molecular geometry: tetrahedral

          Bond polarity: C-Cl bond nonpolar

  Molecular polarity: nonpolar (symmetrical molecule. All bond dipoles cancel)

        Strongest IMF: London dispersion forces

 Solubility in water: low

A nonpolar molecule is insoluble in a polar solvent.

d) PH₃

  Electron geometry: tetrahedral

Molecular geometry: trigonal pyramidal

          Bond polarity: P-H bonds are polar

  Molecular polarity: polar (all P-H bond dipoles point towards P)

         Strongest IMF: dipole-dipole

  Solubility in water: soluble

A polar molecule is soluble in a polar solvent.

c) NH₃

  Electron geometry: tetrahedral

Molecular geometry: trigonal pyramidal

          Bond polarity: N-H bonds are highly polar

  Molecular polarity:  highly polar (all N-H bond dipoles point towards N)

         Strongest IMF: hydrogen bonding

  Solubility in water: highly soluble

NH₃ is so polar that it can form hydrogen bonds with water.

$\boxed{\textbf{The compound with the greatest solubility in water is NH _{3} }}$