In each of the following groups of substances, pick the one that has the given property. Justify your answer. a) highest boiling point: HBr, Kr, Cl2 b) highest freezing point: H2O, NaCl, Hf c) lowest vapor pressure at 25C: Cl2, Br2, I2 d) lowest freezing point: N2, CO, CO2 e) lowest boiling point: CH4, CH3CH3, CH3CH2CH3 f) highest boiling point: HF, HCl, HBr Could someone help me understand fully how to do this?

The intermolecular forces in the compound have been responsible for the various properties of the compounds.

(a) Highest boiling point:

The hydrogen bonding has resulted from the electrostatic interaction of the H with the more electronegative atom. The strong interaction results in a higher boiling point.

HBr has consisted of the hydrogen bond, thus having the highest boiling point.

(b) Highest freezing point:

The higher hydrogen bonding in the structure results in a high freezing point. The ionic compounds with electrostatic interactions result in a high freezing point.

NaCl has been an ionic compound, thus has been consisted of the highest freezing point.

(c) Lowe vapor pressure:

Vapor pressure has been inversely proportional to the molecular mass. The higher the molecular weight, the lower has been the vapor pressure.

Iodine has the highest molecular weight, thereby has the lowest vapor pressure.

(d) Lowest freezing point:

Based on the molecular weight, the lower the molecular weight, the lower has been the freezing point of the molecule.

The has the lowest molecular weight, thus the lowest freezing point.

(e) Highest boiling point:

The more electronegative atom in the hydrogen bonding, the higher has been the stability and the higher the boiling point.

HF has the highest boiling point as it has H bonded with the most electronegative element.

For more information about the boiling and freezing point, refer to the link:

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A) HBr

b) NaCl

c) I2

d) N2

e) CH4

f) HF

Explanation:

a) HBr has the highest boiling point because its molecules are held by intermolecular hydrogen bonding unlike other compounds listed.

b) the freezing point of a substance is the same as its melting point. Ionic substances have the highest melting points. Hence NaCl has a melting (freezing) point of about 801°C

c) vapour pressure depends on molecular mass. The higher the molecular mass the lower the vapour pressure. I2 has the highest relative molecular mass and hence the lowest vapour pressure.

d) The molecule with the lowest molecular mass is expected to have the lowest intermolecular dispersion forces and hence the lowest freezing point.

e) Degree of dispersion forces and boiling point increases with increase in molecular mass. Since CH4 has the lowest molecular mass, it will also possess the lowest boiling point.

e) The magnitude of electro negativity decreases down the group. Hence, fluorine is the most electronegative element among the halogens. Hydrogen bonding results when hydrogen is covalently bonded to an electronegative element. The strength of the hydrogen bonding depends on the electro negativity of the electronegative element.

For hydrogen halides, HF has the highest boiling point since F is the most electronegative halogen and HF possess the greatest degree of hydrogen bonding among the hydrogen halides. Hydrogen bonding leads to increase in boiling point of substances.