,Verified CHEM 219 Final Module Exam Principles
of Organic Chemistry w/Lab | Portage (2026–2027)
1. Which of the following sequences correctly arranges the elements in order of increasing
electronegativity?
A) B < C < N < O
B) O < N < C < B
C) C < B < O < N
D) N < O < B < C
Correct Answer: B < C < N < O
Rationale: Electronegativity increases from left to right across a period. Therefore, boron (B) has the
lowest electronegativity, followed by carbon (C), then nitrogen (N), and oxygen (O) has the highest.
The other sequences incorrectly order the elements based on their positions in the periodic table.
2. What is the molecular geometry around a central atom with four bonding domains and zero lone
pairs?
A) Trigonal pyramidal
B) Tetrahedral
C) Bent
D) Square planar
Correct Answer: Tetrahedral
Rationale: Four bonding domains and no lone pairs correspond to a tetrahedral electron-group
geometry and molecular geometry, with bond angles of approximately 109.5°. Trigonal pyramidal
results from three bonds and one lone pair, bent from two bonds and two lone pairs, and square
planar from four bonds and two lone pairs.
3. Which of the following correctly identifies the hybridization and bond angle for a carbon atom in a
triple bond?
,A) sp, 180°
B) sp², 120°
C) sp³, 109.5°
D) sp, 120°
Correct Answer: sp, 180°
Rationale: A carbon atom in a triple bond forms two sigma bonds and has two unhybridized p orbitals,
corresponding to sp hybridization. The geometry is linear with a bond angle of 180°. sp² hybridization
gives 120° bond angles, and sp³ gives 109.5°.
4. Which of the following statements correctly differentiates between sigma (σ) and pi (π) bonds?
A) A sigma bond is formed by side-to-side overlap of p orbitals.
B) A pi bond restricts rotation around the bond axis.
C) A sigma bond is weaker than a pi bond.
D) A pi bond is formed by end-to-end overlap of orbitals.
Correct Answer: A pi bond restricts rotation around the bond axis.
Rationale: A pi bond is formed by side-to-side overlap of p orbitals and restricts rotation around the
bond axis. Sigma bonds are formed by end-to-end overlap, allow free rotation, and are generally
stronger than pi bonds. The other options incorrectly describe the orbital overlap or bond strength.
5. What is the correct IUPAC name for the following compound?
CH₃-CH(CH₃)-CH₂-CH₂-CH₃
A) 2-methylpentane
B) 3-methylpentane
C) 2-methylhexane
D) 3-methylhexane
, Correct Answer: 2-methylpentane
Rationale: The longest continuous carbon chain contains five carbons (pentane). A methyl group is
attached to the second carbon to give the lowest possible locant. Therefore, the correct IUPAC name
is 2-methylpentane. The other options have incorrect parent chain lengths or locants.
6. Which of the following is the most stable conformation of cyclohexane?
A) Chair
B) Boat
C) Twist-boat
D) Half-chair
Correct Answer: Chair
Rationale: The chair conformation is the most stable conformation of cyclohexane because it is
completely strain-free, with all bonds staggered and no angle strain. The boat and twist-boat
conformations have steric and torsional strain, and the half-chair is a high-energy transition state.
7. Which of the following correctly describes the relationship between enantiomers?
A) They are non-superimposable mirror images.
B) They are superimposable mirror images.
C) They are constitutional isomers.
D) They have identical physical properties in a chiral environment.
Correct Answer: They are non-superimposable mirror images.
Rationale: Enantiomers are stereoisomers that are non-superimposable mirror images of each other.
They have the same connectivity and identical physical properties in an achiral environment but
rotate plane-polarized light in opposite directions. In a chiral environment, they can have different
properties.
of Organic Chemistry w/Lab | Portage (2026–2027)
1. Which of the following sequences correctly arranges the elements in order of increasing
electronegativity?
A) B < C < N < O
B) O < N < C < B
C) C < B < O < N
D) N < O < B < C
Correct Answer: B < C < N < O
Rationale: Electronegativity increases from left to right across a period. Therefore, boron (B) has the
lowest electronegativity, followed by carbon (C), then nitrogen (N), and oxygen (O) has the highest.
The other sequences incorrectly order the elements based on their positions in the periodic table.
2. What is the molecular geometry around a central atom with four bonding domains and zero lone
pairs?
A) Trigonal pyramidal
B) Tetrahedral
C) Bent
D) Square planar
Correct Answer: Tetrahedral
Rationale: Four bonding domains and no lone pairs correspond to a tetrahedral electron-group
geometry and molecular geometry, with bond angles of approximately 109.5°. Trigonal pyramidal
results from three bonds and one lone pair, bent from two bonds and two lone pairs, and square
planar from four bonds and two lone pairs.
3. Which of the following correctly identifies the hybridization and bond angle for a carbon atom in a
triple bond?
,A) sp, 180°
B) sp², 120°
C) sp³, 109.5°
D) sp, 120°
Correct Answer: sp, 180°
Rationale: A carbon atom in a triple bond forms two sigma bonds and has two unhybridized p orbitals,
corresponding to sp hybridization. The geometry is linear with a bond angle of 180°. sp² hybridization
gives 120° bond angles, and sp³ gives 109.5°.
4. Which of the following statements correctly differentiates between sigma (σ) and pi (π) bonds?
A) A sigma bond is formed by side-to-side overlap of p orbitals.
B) A pi bond restricts rotation around the bond axis.
C) A sigma bond is weaker than a pi bond.
D) A pi bond is formed by end-to-end overlap of orbitals.
Correct Answer: A pi bond restricts rotation around the bond axis.
Rationale: A pi bond is formed by side-to-side overlap of p orbitals and restricts rotation around the
bond axis. Sigma bonds are formed by end-to-end overlap, allow free rotation, and are generally
stronger than pi bonds. The other options incorrectly describe the orbital overlap or bond strength.
5. What is the correct IUPAC name for the following compound?
CH₃-CH(CH₃)-CH₂-CH₂-CH₃
A) 2-methylpentane
B) 3-methylpentane
C) 2-methylhexane
D) 3-methylhexane
, Correct Answer: 2-methylpentane
Rationale: The longest continuous carbon chain contains five carbons (pentane). A methyl group is
attached to the second carbon to give the lowest possible locant. Therefore, the correct IUPAC name
is 2-methylpentane. The other options have incorrect parent chain lengths or locants.
6. Which of the following is the most stable conformation of cyclohexane?
A) Chair
B) Boat
C) Twist-boat
D) Half-chair
Correct Answer: Chair
Rationale: The chair conformation is the most stable conformation of cyclohexane because it is
completely strain-free, with all bonds staggered and no angle strain. The boat and twist-boat
conformations have steric and torsional strain, and the half-chair is a high-energy transition state.
7. Which of the following correctly describes the relationship between enantiomers?
A) They are non-superimposable mirror images.
B) They are superimposable mirror images.
C) They are constitutional isomers.
D) They have identical physical properties in a chiral environment.
Correct Answer: They are non-superimposable mirror images.
Rationale: Enantiomers are stereoisomers that are non-superimposable mirror images of each other.
They have the same connectivity and identical physical properties in an achiral environment but
rotate plane-polarized light in opposite directions. In a chiral environment, they can have different
properties.
