Chapter 3, Problem 3.45P

(a)

Interpretation Introduction

Interpretation: The reason of higher boiling point of methanol ( ${\text{CH}}_{\text{3}}\text{OH}$ ) than methyl mercaptan ( ${\text{CH}}_{\text{3}}\text{SH}$ ) should be explained.

Concept Introduction:

The polar and non-polar covalent compounds can be classified on the basis of polarity of chemical bonds present in the molecule.

The non-polar compounds have same electronegativity of bonded atoms whereas polar covalent are composed of those bonded atoms which have significant difference in their electronegativity.

The polarity of molecule effects the boiling point, vapor pressure and other physical properties because polarity of molecule effects different types of intermolecular interactions such as hydrogen bond, dipole-dipole bond, ion-dipole interactions etc.

(b)

Interpretation Introduction

Interpretation: The reason for slightly higher melting point and boiling point of CO than ${\text{N}}_{\text{2}}$ molecules should be explained.

Concept Introduction:

The polar and non-polar covalent compounds can be classified on the basis of polarity of chemical bonds present in the molecule.

The non-polar compounds have same electronegativity of bonded atoms whereas polar covalent are composed of those bonded atoms which have significant difference in their electronegativity.

The polarity of molecule effects the melting point, boiling point, vapor pressure and other physical properties because polarity of molecule effects different types of intermolecular interactions such as hydrogen bond, dipole-dipole bond, ion-dipole interactions etc.

(c)

Interpretation Introduction

Interpretation: The reason of lower melting point of o-hydroxybenzoic acid compare to meta and para isomers should be explained.

Concept Introduction:

The polar and non-polar covalent compounds can be classified on the basis of polarity of chemical bonds present in the molecule.

The non-polar compounds have same electronegativity of bonded atoms whereas polar covalent are composed of those bonded atoms which have significant difference in their electronegativity.

The polarity of molecule effects the melting point, boiling point, vapor pressure and other physical properties because polarity of molecule effects different types of intermolecular interactions such as hydrogen bond, dipole-dipole bond, ion-dipole interactions etc.

(d)

Interpretation Introduction

Interpretation: The reason of increase of boiling point of the noble gases with atomic number should be explained.

Concept Introduction:

The polar and non-polar covalent compounds can be classified on the basis of polarity of chemical bonds present in the molecule.

The non-polar compounds have same electronegativity of bonded atoms whereas polar covalent are composed of those bonded atoms which have significant difference in their electronegativity.

The polarity of molecule effects the melting point, boiling point, vapor pressure and other physical properties because polarity of molecule effects different types of intermolecular interactions such as hydrogen bond, dipole-dipole bond, ion-dipole interactions etc.

(e)

Interpretation Introduction

Interpretation: The reason of lower vapor pressure of acetic acid in the gas phase compare to the predicted value from the ideal gas law should be explained.

Concept Introduction:

The polar and non-polar covalent compounds can be classified on the basis of polarity of chemical bonds present in the molecule.

The non-polar compounds have same electronegativity of bonded atoms whereas polar covalent are composed of those bonded atoms which have significant difference in their electronegativity.

The polarity of molecule effects the melting point, boiling point, vapor pressure and other physical properties because polarity of molecule effects different types of intermolecular interactions such as hydrogen bond, dipole-dipole bond, ion-dipole interactions etc.

(f)

Interpretation Introduction

Interpretation: The reason of negative deviation of a mixture of acetone and chloroform from the Raoult’s law should be explained.

Concept Introduction:

When a non-volatile solute is dissolved in solvent to get solution the vapor pressure decreases for the solution and it can be calculated with the help of Raoult’s law that states that the vapor pressure of solution is the product of mole fraction of solvent and vapor pressure of pure solvent. When a volatile solute is added to the solvent the overall vapor pressure of solution will be the sum of vapor pressure contribution of individual component.

The mathematical expression can be written as:

  ${\text{P}}_{\text{solution }}{\text{= [χ}}_{\text{A}}{\text{× P}}_{\text{A}}]+{\text{[χ}}_{\text{B}}{\text{× P}}_{\text{B}}]$

(g)

Interpretation Introduction

Interpretation: The reason of greater bond dissociation energy of CO (1072 kJ/mol) than molecular nitrogen (945 kJ/mol) should be explained.

Concept Introduction:

The polar and non-polar covalent compounds can be classified on the basis of polarity of chemical bonds present in the molecule.

The non-polar compounds have same electronegativity of bonded atoms whereas polar covalent are composed of those bonded atoms which have significant difference in their electronegativity.

The polarity of molecule effects the boiling point, vapor pressure and other physical properties because polarity of molecule effects different types of intermolecular interactions such as hydrogen bond, dipole-dipole bond, ion-dipole interactions etc.