Question

Decide if the following statements regarding Intermolecular forces are True or False. 1. HF will have a higher vapor pressure at 25oC than KCl. 2. CH3CH2OH will have a higher melting point than CH3OCH3. 3. As the polarity of a covalent compound increases, the solubility of the compound in CCl4 decreases. 4. NH3 will have a lower vapor pressure at -50oC than NO. 5. CH3CH2CH3 will have a higher boiling point than CH3CH3. Please explain the answers as well.

Answer 1

Explanation:

1).   In a HF molecule there will be dipole forces due to difference in electronegativity of both hydrogen and fluorine atom. Hence, there will exist weak intermolecular forces as compared to the intermolecular forces between KCl.

So, the statement HF will have a higher vapor pressure at $25^{o}C$ than KCl is true.

2).  In $CH_{3}CH_{2}OH$ molecule, there will be hydrogen bonding which is stronger than dipole forces. Hence, it will have high melting point. Whereas in $CH_{3}OCH_{3}$ there will be dipole forces due to which there will be weak intermolecular forces leading to low melting point.

Therefore, the statement $CH_{3}CH_{2}OH$ will have a higher melting point than $CH_{3}OCH_{3}$, is true.

3).   Since, like dissolves like. So, with increase in polarity of a covalent compound there will occur a decrease in solubility of the compound in $CCl_{4}$ because $CCl_{4}$ is a non-polar solvent.

Hence, the statement as the polarity of a covalent compound increases, the solubility of the compound in  $CCl_{4}$ decreases, is true.

4).    In $NH_{3}$ molecule there will be hydrogen bonding due to which it will have strong intermolecular forces leading to a lower vapor pressure as compared to NO in which dipole forces exist.

Hence, the statement $NH_{3}$ will have a lower vapor pressure at $-50^{o}C$ than NO, is true.

5).   Longer is the hydrocarbon chain more will be its boiling point. Hence, the statement $CH_3CH_2CH_3$ will have a higher boiling point than CH_3CH_3, is true.