Which of the following best describes the octet rule in covalent bonding?

A. Atoms tend to lose or gain electrons to achieve a full outer shell of 8 electrons.

B. Atoms always have 8 electrons in their outermost shell.

C. Atoms bond covalently to achieve a total of 8 atoms.

D. Atoms always share 8 electrons in a covalent bond.

Which type of covalent bond involves the sharing of six electrons between two atoms?

A. Single bond

B. Double bond

C. Triple bond

D. Quadruple bond

Which molecule is non-polar despite having polar covalent bonds?

A. H2O

B. CO2

C. NH3

D. HCl

Which of the following molecules has the highest dipole moment?

A. CH4

B. NH3

C. H2O

D. BF3

Which of the following best describes the bond in Br2?

A. Polar covalent

B. Non-polar covalent

C. Ionic

D. Metallic

a) Describe the difference between a single, double, and triple covalent bond. [3]

b) How does the strength of these bonds vary and why? [2]

a) What is meant by the term 'electronegativity'? [2]

b) How does the difference in electronegativity between two atoms determine the polarity of the bond they form? [3]

a) Explain the significance of the octet rule in covalent bonding. [3]

b) Are there any exceptions to the octet rule? Provide an example. [2]

a) Explain how the concept of hybridisation occurs in covalent bonding and provide an example. [3]

b) Describe the concept of resonance in covalent molecules and its significance. [3]

c) Discuss the effect of bond polarity on the physical properties of covalent compounds. [2]

a) Explain the concept of dipole moment in a covalent bond and how it is determined. [3]

b) Compare and contrast the characteristics of polar and non-polar covalent molecules. [3]

c) Provide an example of a molecule with polar covalent bonds and one with non-polar covalent bonds, and explain the reasons for their polarity or non-polarity. [2]

Which molecule violates the octet rule?

A. CH4

B. BF3

C. CO2

D. NH3

Which of the following has the weakest covalent bond?

A. Triple bond in N2

B. Double bond in O2

C. Single bond in H2

D. Triple bond in C2H2

What determines the polarity of a molecule?

A. The number of electrons

B. The size of the atoms

C. The difference in electronegativity between bonded atoms

D. The number of covalent bonds

Which of the following molecules is polar?

A. BCl3

B. CO2

C. SO2

D. CCl4

How many electrons are shared in a double covalent bond?

A. 1

B. 2

C. 4

D. 6

a) Define the term "electron pair repulsion theory" in the context of molecular geometry. [2]

b) Explain how VSEPR theory helps predict the molecular geometry of covalent molecules. [3]

c) Provide an example of a covalent molecule and determine its molecular geometry using the VSEPR theory, including bond angles. [3]

a) Explain the concept of bond polarity and how it contributes to the formation of hydrogen bonds. [3]

b) Describe the conditions under which hydrogen bonds occur and provide examples of molecules that can form hydrogen bonds. [3]

c) Discuss the significance of hydrogen bonds in biological systems. [2]

a) Explain the concept of the octet rule in covalent bonding and its significance in the stability of molecules. [3]

b) Discuss the exceptions to the octet rule and provide examples of molecules that do not obey the rule. [3]

c) Describe the role of formal charge in determining the most stable Lewis structure of a molecule. [3]

d) Using the Lewis structure, determine the formal charge on each atom in the molecule SO₃ (sulfur trioxide). [2]

a) Explain the concept of bond enthalpy in covalent molecules and how it relates to bond strength. [3]

b) Calculate the bond enthalpy of a carbon-carbon (C-C) single bond using the given bond dissociation energies. [3]

c) Compare the bond enthalpies of a carbon-oxygen (C-O) single bond and a carbon-oxygen (C=O) double bond, and explain the difference. [3]

d) Provide an example of a molecule where resonance structures affect bond enthalpies. [2]

a) Describe the concept of bond polarity and how it relates to electronegativity differences between atoms. [3]

b) Explain the significance of the dipole moment in assessing bond polarity and molecular geometry. [3]

c) Discuss the relationship between bond polarity and the solubility of covalent compounds in polar and non-polar solvents. [3]

d) Provide an example of a molecule with polar covalent bonds and describe its molecular geometry. [2]