Chemistry Test Chemical Bonding 3 — Questions and Answers
Question 1: What is the hybridization of the carbon atom in ethylene (C₂H₄)?
- sp
- sp² (Correct answer)
- sp³
- sp³d
Correct answer: sp²
Carbon in ethylene is sp² hybridized because it forms three sigma bonds and one pi bond via an unhybridized p orbital.
Question 2: Which statement correctly describes a pi (π) bond?
- It forms by end-to-end overlap and allows free rotation
- It forms by lateral overlap of p orbitals and prevents free rotation (Correct answer)
- It is stronger than a sigma bond
- It is the only bond in a single bond
Correct answer: It forms by lateral overlap of p orbitals and prevents free rotation
Pi bonds form through lateral overlap of parallel p orbitals, creating electron density above and below the internuclear axis and restricting rotation.
Question 3: What does bond dissociation energy represent?
- The energy released when a bond forms
- The energy required to break one mole of a bond in the gas phase (Correct answer)
- The energy of electrons in a bond
- The lattice energy of an ionic compound
Correct answer: The energy required to break one mole of a bond in the gas phase
Bond dissociation energy is the energy needed to homolytically break one mole of a specific bond in gaseous molecules.
Question 4: In which compound are the bonds best described as metallic?
- NaCl
- SiO₂
- Cu (Correct answer)
- HCl
Correct answer: Cu
Copper (Cu) is a pure metal where atoms release valence electrons into a delocalized 'sea,' forming metallic bonds.
Question 5: How many lone pairs are on the nitrogen atom in ammonia (NH₃)?
- 0
- 1 (Correct answer)
- 2
- 3
Correct answer: 1
Nitrogen in NH₃ has 5 valence electrons; 3 are used for bonding, leaving 1 lone pair.
Question 6: Which intermolecular force is responsible for the unusually high boiling point of water?
- London dispersion forces
- Dipole-dipole interactions
- Hydrogen bonding (Correct answer)
- Ion-dipole forces
Correct answer: Hydrogen bonding
Hydrogen bonding between water molecules — due to O-H bonds and lone pairs — is unusually strong and elevates the boiling point significantly.
Question 7: What is the formal charge of oxygen in the hydroxide ion (OH⁻)?
- -2
- -1 (Correct answer)
- 0
- +1
Correct answer: -1
Oxygen in OH⁻ has 6 valence electrons, 3 lone pairs (6 electrons), and 1 bonding pair, giving a formal charge of 6 − 6 − ½(2) = −1.
Chemistry Test Chemical Bonding 3
What is the hybridization of the carbon atom in ethylene (C₂H₄)?