AP Chemistry: Chemical Bonding & Molecular Structure 2 — Questions and Answers
Question 1: According to VSEPR theory, what is the molecular geometry of a molecule with two bonding pairs and two lone pairs on the central atom (AX2E2)?
- Linear
- Trigonal planar
- Bent (Correct answer)
- Tetrahedral
Correct answer: Bent
Two bonding pairs and two lone pairs (AX2E2) give a bent molecular shape, as in water.
Question 2: Which molecule contains a coordinate (dative) covalent bond?
- CH4
- NH4+ (Correct answer)
- O2
- CO2
Correct answer: NH4+
In NH4+ the nitrogen lone pair forms a coordinate bond with H+, where both electrons come from nitrogen.
Question 3: What is the hybridization of the carbon atom in a molecule of carbon dioxide (CO2)?
- sp (Correct answer)
- sp2
- sp3
- sp3d
Correct answer: sp
Carbon in CO2 has two electron domains (two double bonds), giving sp hybridization.
Question 4: Which of the following best explains why a water molecule is polar?
- It has nonpolar O-H bonds
- Its bent shape gives an uneven distribution of charge (Correct answer)
- Oxygen is less electronegative than hydrogen
- It has a linear geometry that cancels dipoles
Correct answer: Its bent shape gives an uneven distribution of charge
Water's bent geometry prevents the O-H bond dipoles from canceling, producing a net molecular dipole.
Question 5: How many sigma and pi bonds are present in a molecule of nitrogen gas (N2)?
- 1 sigma, 2 pi (Correct answer)
- 2 sigma, 1 pi
- 3 sigma, 0 pi
- 0 sigma, 3 pi
Correct answer: 1 sigma, 2 pi
A triple bond consists of one sigma bond and two pi bonds, so N2 has 1 sigma and 2 pi bonds.
Question 6: Which intermolecular force is primarily responsible for the unusually high boiling point of HF compared to other hydrogen halides?
- London dispersion forces
- Dipole-dipole only
- Hydrogen bonding (Correct answer)
- Ion-dipole forces
Correct answer: Hydrogen bonding
HF exhibits strong hydrogen bonding because H is bonded to highly electronegative fluorine.
Question 7: What is the formal charge on the central oxygen atom in the ozone molecule (O3) Lewis structure with one single and one double bond?
- -1
- 0
- +1 (Correct answer)
- +2
Correct answer: +1
The central O has one lone pair and three bonds, giving a formal charge of 6 - 2 - 3 = +1.
AP Chemistry: Chemical Bonding & Molecular Structure 2
According to VSEPR theory, what is the molecular geometry of a molecule with two bonding pairs and two lone pairs on the central atom (AX2E2)?