Question 1

Which of the following statements best explains why the bond angle in H2S is approximately 92°, rather than the 109.5° predicted by VSEPR theory?

Accepted Answer

The two unpaired 2p orbitals of sulfur, which are 90° apart, interact with the 1s orbitals of hydrogen, resulting in a smaller bond angle.

Question 2

Which hybridization is required for the central atom in SF6 to explain its observed octahedral geometry?

Accepted Answer

sp3d2

Question 3

In the molecule C2H4 (ethylene), what is the hybridization of each carbon atom, and how are the double bonds formed?

Accepted Answer

Each carbon is sp2 hybridized; the double bond consists of one sigma bond from sp2-sp2 overlap and one pi bond from unhybridized p orbitals.

Question 4

Which of the following best describes the difference between sigma ($$\sigma) $$and pi ($$\pi) $$bonds?

Accepted Answer

A sigma bond is formed by end-to-end overlap of orbitals, while a pi bond is formed by sideways overlap of unhybridized p orbitals.

Question 5

Which of the following molecules requires sp3d hybridization to explain its geometry?

Accepted Answer

PBr5

Question 6

A molecule has a central atom with three bonding pairs and one lone pair of electrons. What is the predicted hybridization and geometry of the central atom?

Accepted Answer

sp3 hybridization; trigonal pyramidal geometry

Question 7

Which of the following best explains why the bond angle in water (H2O) is 105°, rather than the ideal tetrahedral angle of 109.5°?

Accepted Answer

The two lone pairs on oxygen repel the bonding pairs more strongly, compressing the bond angle.

Question 8

In the molecule BeCl2, what is the hybridization of the central atom and the resulting molecular geometry?

Accepted Answer

sp hybridization; linear geometry

Question 9

Which of the following statements about the formation of covalent bonds according to valence bond theory is correct?

Accepted Answer

A covalent bond forms when two singly occupied atomic orbitals overlap and the electrons have opposite spins.

Question 10

Which of the following best describes the bonding in formaldehyde (CH2O)?

Accepted Answer

The carbon atom is sp2 hybridized, forming two sigma bonds with hydrogen and one sigma bond with oxygen; the remaining unhybridized p orbitals on C and O form a pi bond.

Question 11

Which of the following molecules would you expect to have free rotation about the central bond, and why?

Accepted Answer

C2H4Cl2 (1,2-dichloroethane), because the central bond is a single sigma bond allowing free rotation.

Question 12

A molecule has a central atom with six electron pairs (bonding and lone pairs combined). What is the expected hybridization and geometry?

Accepted Answer

sp3d2 hybridization; octahedral geometry

Question 13

Which of the following best explains why the bond enthalpy of HF is much higher than that of F2?

Accepted Answer

The overlap between the 1s orbital of H and the 2p orbital of F in HF is stronger than the overlap between two 2p orbitals in F2.

Question 14

Which of the following is true regarding the hybridization of the central atom in CO2?

Accepted Answer

The carbon atom is sp hybridized, resulting in a linear geometry with a bond angle of 180°.

Question 15

In the molecule C2H2 (acetylene), how many sigma and pi bonds are present between the two carbon atoms?

Accepted Answer

One sigma bond and two pi bonds

Question 16

Which of the following steps is NOT part of the procedure for determining the hybridization of a central atom in a molecule?

Accepted Answer

Measuring the bond enthalpy experimentally

Question 17

Which of the following molecules contains a central atom that uses d orbitals in its hybridization?

Accepted Answer

SF6

Question 18

Which of the following best describes the energy changes involved in hybridization and bond formation?

Accepted Answer

Hybridization requires energy input, but the energy released during bond formation more than compensates for this, resulting in a net energy decrease.

Question 19

Which of the following is a correct statement about the relationship between the number of electron pairs around a central atom and its hybridization?

Accepted Answer

Four electron pairs require sp3 hybridization, resulting in a tetrahedral geometry.

chapter 8 part 1

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