CHM 2210 Exam 1 V1 | CHM 2210 Organic Chemistry I | Actual Q&A
with Rationale (CHM2210 Exam 1) | University of Central Florida
1. Which of the following elements is the most electronegative based on periodic trends
discussed in CHM 2210?
A. Fluorine
B. Nitrogen
C. Carbon
D. Oxygen
Correct Answer: A
Explanation: Fluorine is the most electronegative element on the periodic table because it
has the highest effective nuclear charge relative to its atomic radius. Electronegativity
increases as one moves across a period from left to right and decreases as one moves down
a group. Therefore, fluorine exerts the strongest pull on shared electrons in a covalent
bond.
2. What is the hybridization of the central carbon atom in a molecule of carbon dioxide
(CO2)?
A. p
B. sp2
C. sp3
D. sp
Correct Answer: D
Explanation: The central carbon in CO2 forms two double bonds with two oxygen atoms
and has no lone pairs, giving it a steric number of two. According to VSEPR theory, a steric
number of two corresponds to sp hybridization and a linear geometry. This arrangement
minimizes the repulsion between the two electron domains surrounding the carbon atom.
3. Calculate the formal charge of the nitrogen atom in the ammonium ion (NH4+).
A. 0
B. -1
C. +2
D. +1
Correct Answer: D
,Explanation: Nitrogen normally has five valence electrons, but in the ammonium ion, it
shares four pairs of electrons in covalent bonds. The formal charge formula is valence
electrons minus [lone pair electrons + 0.5 * bonding electrons], which results in 5 - 4 = +1.
This positive charge is localized on the nitrogen atom, making the overall ion cationic.
4. Which of the following molecules contains a polar covalent bond but is overall nonpolar?
A. CCl4
B. H2O
C. NH3
D. CH3Cl
Correct Answer: A
Explanation: Carbon tetrachloride contains four polar C-Cl bonds where chlorine is more
electronegative than carbon. However, the tetrahedral geometry of the molecule causes the
individual bond dipoles to cancel each other out perfectly. Consequently, the net molecular
dipole moment is zero, rendering the molecule nonpolar.
5. Which factor is the most significant in determining the relative acidity of HCl vs. HF?
A. Bond strength/Size
B. Electronegativity
C. Resonance
D. Inductive effects
Correct Answer: A
Explanation: When comparing atoms in the same group, the size of the atom is more
important than electronegativity for determining acidity. Chlorine is larger than fluorine,
meaning the H-Cl bond is longer and weaker, and the chloride ion is better at stabilizing the
negative charge due to its larger surface area. As a result, HCl is a much stronger acid than
HF in aqueous solutions.
6. Identify the hybridization of the oxygen atom in a molecule of dimethyl ether (CH3OCH3).
A. sp3
B. sp2
C. sp
D. p
Correct Answer: A
Explanation: The oxygen atom in dimethyl ether is bonded to two carbon atoms and
possesses two lone pairs of electrons. Summing these regions of electron density gives a
, steric number of four, which necessitates sp3 hybridization. The resulting molecular
geometry is bent, similar to the structure of water.
7. In the resonance structures of the acetate ion (CH3COO-), how many electrons are involved
in the delocalized pi system?
A. 2
B. 4
C. 6
D. 8
Correct Answer: B
Explanation: The delocalized pi system in the carboxylate group of the acetate ion consists
of one pi bond and one lone pair that can shift through resonance. Specifically, two
electrons from the C=O pi bond and two electrons from a lone pair on the anionic oxygen
participate. This total of four electrons allows the negative charge to be shared equally
between both oxygen atoms.
8. Which of the following is the correct IUPAC name for a five-carbon unbranched alkane?
A. Pentane
B. Hexane
C. Butane
D. Propane
Correct Answer: A
Explanation: The IUPAC prefix ‘pent-’ signifies a chain of five carbon atoms. Since the
molecule is an alkane, it follows the CnH2n+2 formula and ends with the suffix ‘-ane’.
Therefore, pentane is the systematic name for the straight-chain structure containing five
carbons.
9. Which conformation of butane is the most stable according to Newman projection
analysis?
A. Gauche
B. Eclipsed
C. Anti
D. Totally Eclipsed
Correct Answer: C
Explanation: In the anti conformation, the two large methyl groups are positioned 180
degrees apart from each other. This maximizes the distance between the groups and
with Rationale (CHM2210 Exam 1) | University of Central Florida
1. Which of the following elements is the most electronegative based on periodic trends
discussed in CHM 2210?
A. Fluorine
B. Nitrogen
C. Carbon
D. Oxygen
Correct Answer: A
Explanation: Fluorine is the most electronegative element on the periodic table because it
has the highest effective nuclear charge relative to its atomic radius. Electronegativity
increases as one moves across a period from left to right and decreases as one moves down
a group. Therefore, fluorine exerts the strongest pull on shared electrons in a covalent
bond.
2. What is the hybridization of the central carbon atom in a molecule of carbon dioxide
(CO2)?
A. p
B. sp2
C. sp3
D. sp
Correct Answer: D
Explanation: The central carbon in CO2 forms two double bonds with two oxygen atoms
and has no lone pairs, giving it a steric number of two. According to VSEPR theory, a steric
number of two corresponds to sp hybridization and a linear geometry. This arrangement
minimizes the repulsion between the two electron domains surrounding the carbon atom.
3. Calculate the formal charge of the nitrogen atom in the ammonium ion (NH4+).
A. 0
B. -1
C. +2
D. +1
Correct Answer: D
,Explanation: Nitrogen normally has five valence electrons, but in the ammonium ion, it
shares four pairs of electrons in covalent bonds. The formal charge formula is valence
electrons minus [lone pair electrons + 0.5 * bonding electrons], which results in 5 - 4 = +1.
This positive charge is localized on the nitrogen atom, making the overall ion cationic.
4. Which of the following molecules contains a polar covalent bond but is overall nonpolar?
A. CCl4
B. H2O
C. NH3
D. CH3Cl
Correct Answer: A
Explanation: Carbon tetrachloride contains four polar C-Cl bonds where chlorine is more
electronegative than carbon. However, the tetrahedral geometry of the molecule causes the
individual bond dipoles to cancel each other out perfectly. Consequently, the net molecular
dipole moment is zero, rendering the molecule nonpolar.
5. Which factor is the most significant in determining the relative acidity of HCl vs. HF?
A. Bond strength/Size
B. Electronegativity
C. Resonance
D. Inductive effects
Correct Answer: A
Explanation: When comparing atoms in the same group, the size of the atom is more
important than electronegativity for determining acidity. Chlorine is larger than fluorine,
meaning the H-Cl bond is longer and weaker, and the chloride ion is better at stabilizing the
negative charge due to its larger surface area. As a result, HCl is a much stronger acid than
HF in aqueous solutions.
6. Identify the hybridization of the oxygen atom in a molecule of dimethyl ether (CH3OCH3).
A. sp3
B. sp2
C. sp
D. p
Correct Answer: A
Explanation: The oxygen atom in dimethyl ether is bonded to two carbon atoms and
possesses two lone pairs of electrons. Summing these regions of electron density gives a
, steric number of four, which necessitates sp3 hybridization. The resulting molecular
geometry is bent, similar to the structure of water.
7. In the resonance structures of the acetate ion (CH3COO-), how many electrons are involved
in the delocalized pi system?
A. 2
B. 4
C. 6
D. 8
Correct Answer: B
Explanation: The delocalized pi system in the carboxylate group of the acetate ion consists
of one pi bond and one lone pair that can shift through resonance. Specifically, two
electrons from the C=O pi bond and two electrons from a lone pair on the anionic oxygen
participate. This total of four electrons allows the negative charge to be shared equally
between both oxygen atoms.
8. Which of the following is the correct IUPAC name for a five-carbon unbranched alkane?
A. Pentane
B. Hexane
C. Butane
D. Propane
Correct Answer: A
Explanation: The IUPAC prefix ‘pent-’ signifies a chain of five carbon atoms. Since the
molecule is an alkane, it follows the CnH2n+2 formula and ends with the suffix ‘-ane’.
Therefore, pentane is the systematic name for the straight-chain structure containing five
carbons.
9. Which conformation of butane is the most stable according to Newman projection
analysis?
A. Gauche
B. Eclipsed
C. Anti
D. Totally Eclipsed
Correct Answer: C
Explanation: In the anti conformation, the two large methyl groups are positioned 180
degrees apart from each other. This maximizes the distance between the groups and
