CHM 2210 Exam 1 V2 | CHM 2210 Organic Chemistry I | Actual Q&A
with Rationale (CHM2210 Exam 1) | University of Central Florida
1. How many valence electrons does a neutral carbon atom possess?
A. 4
B. 2
C. 6
D. 8
Answer: A
Explanation: Carbon is located in Group 14 of the periodic table, indicating it has four
electrons in its outermost shell. These valence electrons are primarily involved in chemical
bonding and determine the atom’s reactivity. Understanding valence electron count is
fundamental for drawing correct Lewis structures in organic chemistry.
2. What is the hybridization of the carbon atoms in a molecule of ethane (C2H6)?
A. sp
B. sp3
C. sp2
D. p3
Answer: B
Explanation: In ethane, each carbon atom is bonded to four other atoms through single
sigma bonds. This tetrahedral arrangement requires four equivalent hybrid orbitals
derived from the s and three p orbitals. Thus, the hybridization state is identified as sp3 to
accommodate the molecular geometry.
3. Which of the following describes the bond angle typically associated with sp2 hybridized
carbon atoms?
A. 109.5 degrees
B. 180 degrees
C. 120 degrees
D. 90 degrees
Answer: C
,Explanation: Carbon atoms that are sp2 hybridized possess a trigonal planar electron
geometry. This geometry results in bond angles of approximately 120 degrees between the
substituents. This configuration is commonly observed in molecules containing carbon-
carbon double bonds like ethylene.
4. In the context of acid-base chemistry, which molecule is considered the strongest
Brønsted-Lowry acid?
A. CH4
B. NH3
C. HI
D. H2O
Answer: C
Explanation: Acid strength increases as we move down a group in the periodic table due to
the increase in atomic size. Hydroiodic acid has the weakest H-I bond and the most stable
conjugate base among the provided options. Consequently, HI displays a much lower pKa
value compared to methane, ammonia, or water.
5. What is the formal charge on the nitrogen atom in the ammonium ion (NH4+)?
A. -1
B. 0
C. +1
D. +2
Answer: C
Explanation: Nitrogen normally possesses five valence electrons in its neutral state. In the
ammonium ion, nitrogen is bonded to four hydrogen atoms and has zero lone pairs. Using
the formal charge formula, we subtract four from five, resulting in a net formal charge of
+1.
6. Which molecular geometry is associated with a molecule of carbon dioxide (CO2)?
A. Bent
B. Trigonal Planar
C. Linear
D. Tetrahedral
Answer: C
Explanation: The central carbon atom in carbon dioxide is double-bonded to two oxygen
atoms and possesses no lone pairs. This results in an sp hybridization state for the carbon
, atom. The VSEPR theory dictates that two electron domains will orient themselves 180
degrees apart, creating a linear shape.
7. Which rule states that electrons must fill degenerate orbitals individually before pairing
up?
A. Aufbau Principle
B. Hund’s Rule
C. Pauli Exclusion Principle
D. Octet Rule
Answer: B
Explanation: Hund’s Rule governs the way electrons occupy orbitals of the same energy
level. It minimizes electron-electron repulsion by keeping electrons in separate orbitals
with parallel spins. This concept is vital when determining the electronic ground state of
atoms like nitrogen or carbon.
8. Which of the following functional groups contains a nitrogen atom double-bonded to an
oxygen atom?
A. Amine
B. Amide
C. Nitrile
D. Nitro
Answer: D
Explanation: The nitro group (NO2) features a nitrogen atom bonded to two oxygen
atoms, where resonance involves a double bond. Amides consist of a nitrogen adjacent to a
carbonyl group, while amines contain only single bonds to nitrogen. Identifying these
groups is a primary skill required for CHM 2210 examinations.
9. What is the relationship between two molecules that have the same molecular formula but
different connectivity?
A. Conformers
B. Stereoisomers
C. Enantiomers
D. Constitutional Isomers
Answer: D
Explanation: Constitutional isomers, also known as structural isomers, differ in the
sequence in which atoms are linked. Despite sharing the same molecular formula, their
with Rationale (CHM2210 Exam 1) | University of Central Florida
1. How many valence electrons does a neutral carbon atom possess?
A. 4
B. 2
C. 6
D. 8
Answer: A
Explanation: Carbon is located in Group 14 of the periodic table, indicating it has four
electrons in its outermost shell. These valence electrons are primarily involved in chemical
bonding and determine the atom’s reactivity. Understanding valence electron count is
fundamental for drawing correct Lewis structures in organic chemistry.
2. What is the hybridization of the carbon atoms in a molecule of ethane (C2H6)?
A. sp
B. sp3
C. sp2
D. p3
Answer: B
Explanation: In ethane, each carbon atom is bonded to four other atoms through single
sigma bonds. This tetrahedral arrangement requires four equivalent hybrid orbitals
derived from the s and three p orbitals. Thus, the hybridization state is identified as sp3 to
accommodate the molecular geometry.
3. Which of the following describes the bond angle typically associated with sp2 hybridized
carbon atoms?
A. 109.5 degrees
B. 180 degrees
C. 120 degrees
D. 90 degrees
Answer: C
,Explanation: Carbon atoms that are sp2 hybridized possess a trigonal planar electron
geometry. This geometry results in bond angles of approximately 120 degrees between the
substituents. This configuration is commonly observed in molecules containing carbon-
carbon double bonds like ethylene.
4. In the context of acid-base chemistry, which molecule is considered the strongest
Brønsted-Lowry acid?
A. CH4
B. NH3
C. HI
D. H2O
Answer: C
Explanation: Acid strength increases as we move down a group in the periodic table due to
the increase in atomic size. Hydroiodic acid has the weakest H-I bond and the most stable
conjugate base among the provided options. Consequently, HI displays a much lower pKa
value compared to methane, ammonia, or water.
5. What is the formal charge on the nitrogen atom in the ammonium ion (NH4+)?
A. -1
B. 0
C. +1
D. +2
Answer: C
Explanation: Nitrogen normally possesses five valence electrons in its neutral state. In the
ammonium ion, nitrogen is bonded to four hydrogen atoms and has zero lone pairs. Using
the formal charge formula, we subtract four from five, resulting in a net formal charge of
+1.
6. Which molecular geometry is associated with a molecule of carbon dioxide (CO2)?
A. Bent
B. Trigonal Planar
C. Linear
D. Tetrahedral
Answer: C
Explanation: The central carbon atom in carbon dioxide is double-bonded to two oxygen
atoms and possesses no lone pairs. This results in an sp hybridization state for the carbon
, atom. The VSEPR theory dictates that two electron domains will orient themselves 180
degrees apart, creating a linear shape.
7. Which rule states that electrons must fill degenerate orbitals individually before pairing
up?
A. Aufbau Principle
B. Hund’s Rule
C. Pauli Exclusion Principle
D. Octet Rule
Answer: B
Explanation: Hund’s Rule governs the way electrons occupy orbitals of the same energy
level. It minimizes electron-electron repulsion by keeping electrons in separate orbitals
with parallel spins. This concept is vital when determining the electronic ground state of
atoms like nitrogen or carbon.
8. Which of the following functional groups contains a nitrogen atom double-bonded to an
oxygen atom?
A. Amine
B. Amide
C. Nitrile
D. Nitro
Answer: D
Explanation: The nitro group (NO2) features a nitrogen atom bonded to two oxygen
atoms, where resonance involves a double bond. Amides consist of a nitrogen adjacent to a
carbonyl group, while amines contain only single bonds to nitrogen. Identifying these
groups is a primary skill required for CHM 2210 examinations.
9. What is the relationship between two molecules that have the same molecular formula but
different connectivity?
A. Conformers
B. Stereoisomers
C. Enantiomers
D. Constitutional Isomers
Answer: D
Explanation: Constitutional isomers, also known as structural isomers, differ in the
sequence in which atoms are linked. Despite sharing the same molecular formula, their
