Q13.9 P - Chemistry: Molecular Nature Of Matter And Change

Question

What is the strongest type of intermolecular force between

solute and solvent in each solution?

(a) $\mathbf{CsCl}\left(\mathbf{s}\right)$ in ${\mathbf{H}}_{\mathbf{2}}\mathbf{O}\left(\mathbf{l}\right)$

(b) ${\mathbf{CH}}_{\mathbf{3}}{\mathbf{COCH}}_{\mathbf{3}}\left(\mathbf{l}\right)$ in ${\mathbf{H}}_{\mathbf{2}}\mathbf{O}\left(\mathbf{l}\right)$

(c) ${\mathbf{CH}}_{\mathbf{3}}\mathbf{OH}\left(\mathbf{l}\right)$ in ${\mathbf{CCl}}_{\mathbf{4}}\left(\mathbf{l}\right)$

Step-by-Step Solution

Answer

(a) $\mathbf{CsCl}\left(\mathbf{s}\right){\mathbf{inH}}_{\mathbf{2}}\mathbf{O}\left(\mathbf{l}\right)\mathbf{=}\mathbf{Iondipoleforces}$

(b) ${\mathbf{CH}}_{\mathbf{3}}{\mathbf{COCH}}_{\mathbf{3}}\left(\mathbf{l}\right){\mathbf{inH}}_{\mathbf{2}}\mathbf{O}\mathbf{\left(}\mathbf{l}\mathbf{\right)}\mathbf{=}\mathbf{Hydrogenbonding}$

(c) ${\mathbf{CH}}_{\mathbf{3}}\mathbf{OH}\left(\mathbf{l}\right){\mathbf{inCCl}}_{\mathbf{4}}\left(\mathbf{l}\right)\mathbf{=}\mathbf{Dipoleinduceddipoleforces}$

Step 1: Ion dipole forces

(a)

These are the principal force involved in the solubility of ionic compounds in water. When $\mathbf{CsCl}$ dissolves, each ion on the crystal’s surface attracts the oppositely charged end of the water dipole. The crystal structure is destroyed by these attractive forces, which outweigh those between the ions. As each ion becomes separated, more water molecules cluster around it.

Step 2: Hydrogen bonding

(b)

These are the forces of attraction between an H atom with a strongly electronegative atom. These are found in many oxygens- and nitrogen-containing organic and biological compounds, such as alcohols, sugars, amines, and amino acids. 

O of ${\mathbf{CH}}_{\mathbf{3}}{\mathbf{COCH}}_{\mathbf{3}}$ is small and electronegative, so it can get very close to the O of ${\mathbf{H}}_{\mathbf{2}}\mathbf{O}$.

Step 3: Dipole-induced dipole forces

These are based on polarizability. They arise when a polar molecule distorts the electron cloud of a nearby nonpolar molecule. 

${\mathbf{CH}}_{\mathbf{3}}\mathbf{OH}$ is a polar molecule that has some dipole character to it and it induced dipole to non-polar ${\mathbf{CCl}}_{\mathbf{4}}$.