CHM 2210 Exam 1 V3 | 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
Correct Answer: A
Explanation: A neutral carbon atom is located in Group 4A of the periodic table, indicating
it has four electrons in its outermost shell. These valence electrons are essential for
forming the four covalent bonds typically seen in organic molecules. Understanding
valence electron count is the first step in constructing accurate Lewis structures for organic
compounds.
2. Which of the following elements is the most electronegative?
A. Fluorine
B. Nitrogen
C. Oxygen
D. Carbon
Correct Answer: A
Explanation: Electronegativity increases as one moves from left to right and from bottom
to top on the periodic table. Fluorine is positioned at the top right, making it the most
electronegative element with a value of approximately 4.0. This property is crucial in
determining bond polarity and the distribution of electron density within a molecule.
3. What is the formal charge on the nitrogen atom in the ammonium ion (NH4+)?
A. -1
B. 0
C. +1
D. +2
Correct Answer: C
,Explanation: The formal charge is determined by subtracting the number of non-bonding
electrons and half of the bonding electrons from the atom’s valence electrons. In the
ammonium ion, nitrogen has five valence electrons but is sharing four pairs with no lone
pairs. This calculation (5 minus 4) results in a formal charge of positive one on the nitrogen
atom.
4. Which hybridization state corresponds to a carbon atom involved in a triple bond?
A. sp3
B. sp2
C. sp
D. s
Correct Answer: C
Explanation: A carbon atom in a triple bond is bonded to two other atoms and has two
regions of electron density. To minimize repulsion, these regions adopt a linear geometry,
which requires sp hybridization. This process leaves two unhybridized p-orbitals available
to form the two pi bonds of the triple bond.
5. What is the approximate bond angle in a molecule with sp2 hybridized carbon atoms, such
as ethene?
A. 90 degrees
B. 120 degrees
C. 109.5 degrees
D. 180 degrees
Correct Answer: B
Explanation: In sp2 hybridization, the three hybrid orbitals are arranged in a trigonal
planar geometry to maximize separation. This arrangement results in ideal bond angles of
approximately 120 degrees between the atoms. Deviations from this angle may occur if
there are bulky substituents or lone pairs, but ethene remains very close to this ideal.
6. Which of the following molecules has a net dipole moment of zero?
A. CH3Cl
B. H2O
C. NH3
D. CCl4
Correct Answer: D
, Explanation: While individual C-Cl bonds are polar, the tetrahedral geometry of carbon
tetrachloride allows the four bond dipoles to cancel each other out. Because the molecule is
perfectly symmetrical, the vector sum of the dipoles is zero. This lack of a net dipole
moment makes the molecule nonpolar despite containing polar covalent bonds.
7. Which functional group is characterized by a carbon-oxygen double bond (C=O) bonded to
two other carbon atoms?
A. Aldehyde
B. Alcohol
C. Carboxylic acid
D. Ketone
Correct Answer: D
Explanation: A ketone consists of a carbonyl group where the carbon is bonded to two
alkyl or aryl groups. If one of those groups were a hydrogen atom, the functional group
would be classified as an aldehyde instead. This structural distinction is vital for
understanding the reactivity and chemical properties of carbonyl compounds.
8. According to the Bronsted-Lowry definition, what is a base?
A. A proton donor
B. An electron pair acceptor
C. An electron pair donor
D. A proton acceptor
Correct Answer: D
Explanation: The Bronsted-Lowry theory defines acids and bases based on the transfer of
protons (H+). A base is any species that can accept a proton from an acid during a chemical
reaction. This definition is broader than the Arrhenius definition and is frequently used in
organic mechanism analysis.
9. Which of the following factors does NOT increase the acidity of a compound?
A. Decreased s-character in the orbital holding the lone pair
B. Inductive electron withdrawal
C. Resonance stabilization of the conjugate base
D. High electronegativity of the atom attached to H
Correct Answer: A
Explanation: Increased s-character, such as in sp orbitals, places electrons closer to the
nucleus and stabilizes the conjugate base, thereby increasing acidity. Conversely, decreased
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
Correct Answer: A
Explanation: A neutral carbon atom is located in Group 4A of the periodic table, indicating
it has four electrons in its outermost shell. These valence electrons are essential for
forming the four covalent bonds typically seen in organic molecules. Understanding
valence electron count is the first step in constructing accurate Lewis structures for organic
compounds.
2. Which of the following elements is the most electronegative?
A. Fluorine
B. Nitrogen
C. Oxygen
D. Carbon
Correct Answer: A
Explanation: Electronegativity increases as one moves from left to right and from bottom
to top on the periodic table. Fluorine is positioned at the top right, making it the most
electronegative element with a value of approximately 4.0. This property is crucial in
determining bond polarity and the distribution of electron density within a molecule.
3. What is the formal charge on the nitrogen atom in the ammonium ion (NH4+)?
A. -1
B. 0
C. +1
D. +2
Correct Answer: C
,Explanation: The formal charge is determined by subtracting the number of non-bonding
electrons and half of the bonding electrons from the atom’s valence electrons. In the
ammonium ion, nitrogen has five valence electrons but is sharing four pairs with no lone
pairs. This calculation (5 minus 4) results in a formal charge of positive one on the nitrogen
atom.
4. Which hybridization state corresponds to a carbon atom involved in a triple bond?
A. sp3
B. sp2
C. sp
D. s
Correct Answer: C
Explanation: A carbon atom in a triple bond is bonded to two other atoms and has two
regions of electron density. To minimize repulsion, these regions adopt a linear geometry,
which requires sp hybridization. This process leaves two unhybridized p-orbitals available
to form the two pi bonds of the triple bond.
5. What is the approximate bond angle in a molecule with sp2 hybridized carbon atoms, such
as ethene?
A. 90 degrees
B. 120 degrees
C. 109.5 degrees
D. 180 degrees
Correct Answer: B
Explanation: In sp2 hybridization, the three hybrid orbitals are arranged in a trigonal
planar geometry to maximize separation. This arrangement results in ideal bond angles of
approximately 120 degrees between the atoms. Deviations from this angle may occur if
there are bulky substituents or lone pairs, but ethene remains very close to this ideal.
6. Which of the following molecules has a net dipole moment of zero?
A. CH3Cl
B. H2O
C. NH3
D. CCl4
Correct Answer: D
, Explanation: While individual C-Cl bonds are polar, the tetrahedral geometry of carbon
tetrachloride allows the four bond dipoles to cancel each other out. Because the molecule is
perfectly symmetrical, the vector sum of the dipoles is zero. This lack of a net dipole
moment makes the molecule nonpolar despite containing polar covalent bonds.
7. Which functional group is characterized by a carbon-oxygen double bond (C=O) bonded to
two other carbon atoms?
A. Aldehyde
B. Alcohol
C. Carboxylic acid
D. Ketone
Correct Answer: D
Explanation: A ketone consists of a carbonyl group where the carbon is bonded to two
alkyl or aryl groups. If one of those groups were a hydrogen atom, the functional group
would be classified as an aldehyde instead. This structural distinction is vital for
understanding the reactivity and chemical properties of carbonyl compounds.
8. According to the Bronsted-Lowry definition, what is a base?
A. A proton donor
B. An electron pair acceptor
C. An electron pair donor
D. A proton acceptor
Correct Answer: D
Explanation: The Bronsted-Lowry theory defines acids and bases based on the transfer of
protons (H+). A base is any species that can accept a proton from an acid during a chemical
reaction. This definition is broader than the Arrhenius definition and is frequently used in
organic mechanism analysis.
9. Which of the following factors does NOT increase the acidity of a compound?
A. Decreased s-character in the orbital holding the lone pair
B. Inductive electron withdrawal
C. Resonance stabilization of the conjugate base
D. High electronegativity of the atom attached to H
Correct Answer: A
Explanation: Increased s-character, such as in sp orbitals, places electrons closer to the
nucleus and stabilizes the conjugate base, thereby increasing acidity. Conversely, decreased
