What intermolecular forces must be overcome in converting each of the following from liquid to

gas?
(i) Liquid O2 (ii) Mercury (iii) CH3I (methyl iodide) (iv) CH3CH2OH (ethanol

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Hydrogen bond

(i) Liquid O2:

To convert liquid O2 (oxygen) to a gas, the intermolecular forces of attraction known as London dispersion forces must be overcome. Oxygen molecules are held together by weak temporary dipole-induced dipole attractions, which can be easily overcome by adding energy to the system in the form of heat.

(ii) Mercury:
Mercury is a unique substance because it is a metal in a liquid state at room temperature. It does not have intermolecular forces like other liquids. Instead, it has metallic bonding, which is a strong electrostatic force of attraction between positively charged metal ions and delocalized electrons. Therefore, no intermolecular forces need to be overcome to convert liquid mercury to a gas.

(iii) CH3I (methyl iodide):
In the case of CH3I (methyl iodide), the intermolecular forces that need to be overcome to convert it from a liquid to a gas are primarily van der Waals forces. Van der Waals forces include dipole-dipole interactions between the polar CH3I molecules and London dispersion forces. These forces result from temporary fluctuations in electron distribution, creating temporary dipoles and inducing dipoles in neighboring molecules.

(iv) CH3CH2OH (ethanol):
For ethanol (CH3CH2OH), the intermolecular forces that must be overcome to convert it from a liquid to a gas include hydrogen bonding and van der Waals forces. Hydrogen bonding occurs between the hydrogen atoms in one ethanol molecule and the oxygen atom in another ethanol molecule. These interactions are stronger than the London dispersion forces associated with van der Waals forces, but weaker than the covalent bonds within the molecule.

To determine the intermolecular forces that must be overcome in converting each substance from liquid to gas, we need to consider the nature of the molecules and their interactions.

(i) Liquid O2 (oxygen):
Oxygen exists as diatomic molecules (O2) in its liquid and gaseous states. In the liquid state, the intermolecular forces that need to be overcome to convert it to a gas are London dispersion forces, also known as Van der Waals forces. These forces arise due to temporary fluctuations in electron distribution, creating instantaneous dipoles that induce dipoles in neighboring molecules. In the gas phase, the molecules are further apart and have higher kinetic energy, reducing the strength of the London dispersion forces.

(ii) Mercury:
Mercury (Hg) is a metal that exists in a liquid state at room temperature. In its liquid state, mercury exhibits metallic bonding. Metallic bonding is a type of intermolecular force in which metal atoms lose their valence electrons, forming a "sea" of delocalized electrons that are attracted to positively charged metal ions. In order to convert mercury to a gas, these metallic bonds need to be broken and the delocalized electrons need to be disengaged.

(iii) CH3I (methyl iodide):
CH3I, also known as methyl iodide, is a polar molecule due to the difference in electronegativity between carbon and iodine. In its liquid state, the intermolecular forces that need to be overcome to convert it to a gas include dipole-dipole interactions and London dispersion forces. Dipole-dipole interactions occur between the positive end of one molecule (methyl group) and the negative end of another molecule (iodine), resulting in weak attractive forces. Additionally, London dispersion forces also exist between methyl iodide molecules due to temporary electron imbalances.

(iv) CH3CH2OH (ethanol):
Ethanol (CH3CH2OH) is a polar molecule with a hydroxyl (-OH) group. In the liquid state, the intermolecular forces that must be overcome to convert it to a gas include hydrogen bonding, dipole-dipole interactions, and London dispersion forces. Hydrogen bonding occurs between the partially positive hydrogen atom on one ethanol molecule and the partially negative oxygen atom on another molecule. These hydrogen bonds are stronger than dipole-dipole interactions and contribute to the higher boiling point of ethanol compared to similar-sized molecules. Dipole-dipole interactions also exist between the positive end of one molecule (ethyl group) and the negative end of another molecule (oxygen). Additionally, London dispersion forces arise due to temporary electron imbalances.

In summary, converting each substance from liquid to gas requires overcoming different intermolecular forces:
(i) Liquid O2: London dispersion forces
(ii) Mercury: Metallic bonding
(iii) CH3I (methyl iodide): Dipole-dipole interactions and London dispersion forces
(iv) CH3CH2OH (ethanol): Hydrogen bonding, dipole-dipole interactions, and London dispersion forces