CHM 2210 Exam 1 V2 | 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 according to the periodic
trends discussed in CHM 2210?
A. Carbon
B. Nitrogen
C. Fluorine
D. Oxygen
Correct Answer: C
Explanation: Electronegativity increases as you move from left to right across a period and
from bottom to top within a group. Fluorine is positioned at the top right of the periodic
table, excluding noble gases, making it the most electronegative element. This property is
crucial for understanding polar covalent bonds and molecular reactivity in organic
chemistry.
2. What is the hybridization of the carbon atom in a molecule of methane (CH4)?
A. sp3
B. sp2
C. sp
D. p
Correct Answer: A
Explanation: In methane, the central carbon atom is bonded to four hydrogen atoms with
no lone pairs. This steric number of four requires the mixing of one s orbital and three p
orbitals to form four equivalent hybrid orbitals. Consequently, the carbon atom adopts an
sp3 hybridization with a tetrahedral geometry and bond angles of approximately 109.5
degrees.
3. Calculate the formal charge on the nitrogen atom in the ammonium ion (NH4+).
A. 0
B. -1
C. +1
D. +2
Correct Answer: C
,Explanation: Formal charge is calculated by taking the number of valence electrons minus
the sum of non-bonding electrons and half of the bonding electrons. Nitrogen has 5 valence
electrons, and in ammonium, it has 0 lone pair electrons and 4 bonding pairs (8 electrons).
Therefore, 5 - (0 + 4) = +1, which accounts for the positive charge of the ion.
4. Which of the following represents a valid resonance structure for the acetate ion (CH3COO-
)?
A. A structure where an atom is moved to a different position.
B. A structure where carbon has five bonds.
C. A structure where the double bond is shared between the two oxygen atoms through
delocalization.
D. A structure that violates the octet rule for carbon.
Correct Answer: C
Explanation: Resonance involve the movement of electrons, specifically pi electrons and
lone pairs, while the nuclei remain in fixed positions. In the acetate ion, the negative charge
and the pi bond are delocalized over both oxygen atoms. This delocalization provides extra
stability to the conjugate base, which is a key concept in CHM 2210 regarding acid strength.
5. What is the approximate bond angle in an sp2 hybridized carbon atom, such as in
ethylene?
A. 90 degrees
B. 109.5 degrees
C. 180 degrees
D. 120 degrees
Correct Answer: D
Explanation: Sp2 hybridization results from the mixing of one s and two p orbitals,
creating three hybrid orbitals arranged in a trigonal planar geometry. To minimize electron
repulsion according to VSEPR theory, these orbitals are spaced as far apart as possible. This
arrangement results in ideal bond angles of 120 degrees between the substituents.
6. Identify the functional group present in the molecule CH3CH2OH.
A. Alcohol
B. Ether
C. Ketone
D. Aldehyde
Correct Answer: A
, Explanation: The molecule CH3CH2OH contains a hydroxyl (-OH) group attached to a
saturated carbon atom. This specific arrangement characterizes the alcohol functional
group family. Understanding functional groups is essential for naming compounds and
predicting their chemical reactivity throughout the semester.
7. According to the Brønsted-Lowry definition, what is an acid?
A. A proton (H+) donor.
B. An electron pair acceptor.
C. An electron pair donor.
D. A proton (H+) acceptor.
Correct Answer: A
Explanation: The Brønsted-Lowry theory focuses on the transfer of protons between
species during a chemical reaction. A Brønsted-Lowry acid is defined as any substance that
can donate a hydrogen ion (proton) to another molecule. In contrast, a base is the species
that accepts that proton.
8. Which of the following compounds has the lowest pKa value, indicating it is the strongest
acid?
A. CH4
B. NH3
C. HCl
D. H2O
Correct Answer: C
Explanation: The pKa value is the negative logarithm of the acid dissociation constant
(Ka); thus, lower pKa values correspond to stronger acids. HCl is a strong mineral acid with
a negative pKa, whereas water, ammonia, and methane have much higher pKa values.
Hydrochloric acid completely dissociates in aqueous solution, reflecting its high acidity
compared to the others.
9. When comparing the acidity of HF, HCl, HBr, and HI, which is the strongest acid based on
bond strength and conjugate base stability?
A. HI
B. HCl
C. HBr
D. HF
Correct Answer: A
with Rationale (CHM2210 Exam 1) | University of Central Florida
1. Which of the following elements is the most electronegative according to the periodic
trends discussed in CHM 2210?
A. Carbon
B. Nitrogen
C. Fluorine
D. Oxygen
Correct Answer: C
Explanation: Electronegativity increases as you move from left to right across a period and
from bottom to top within a group. Fluorine is positioned at the top right of the periodic
table, excluding noble gases, making it the most electronegative element. This property is
crucial for understanding polar covalent bonds and molecular reactivity in organic
chemistry.
2. What is the hybridization of the carbon atom in a molecule of methane (CH4)?
A. sp3
B. sp2
C. sp
D. p
Correct Answer: A
Explanation: In methane, the central carbon atom is bonded to four hydrogen atoms with
no lone pairs. This steric number of four requires the mixing of one s orbital and three p
orbitals to form four equivalent hybrid orbitals. Consequently, the carbon atom adopts an
sp3 hybridization with a tetrahedral geometry and bond angles of approximately 109.5
degrees.
3. Calculate the formal charge on the nitrogen atom in the ammonium ion (NH4+).
A. 0
B. -1
C. +1
D. +2
Correct Answer: C
,Explanation: Formal charge is calculated by taking the number of valence electrons minus
the sum of non-bonding electrons and half of the bonding electrons. Nitrogen has 5 valence
electrons, and in ammonium, it has 0 lone pair electrons and 4 bonding pairs (8 electrons).
Therefore, 5 - (0 + 4) = +1, which accounts for the positive charge of the ion.
4. Which of the following represents a valid resonance structure for the acetate ion (CH3COO-
)?
A. A structure where an atom is moved to a different position.
B. A structure where carbon has five bonds.
C. A structure where the double bond is shared between the two oxygen atoms through
delocalization.
D. A structure that violates the octet rule for carbon.
Correct Answer: C
Explanation: Resonance involve the movement of electrons, specifically pi electrons and
lone pairs, while the nuclei remain in fixed positions. In the acetate ion, the negative charge
and the pi bond are delocalized over both oxygen atoms. This delocalization provides extra
stability to the conjugate base, which is a key concept in CHM 2210 regarding acid strength.
5. What is the approximate bond angle in an sp2 hybridized carbon atom, such as in
ethylene?
A. 90 degrees
B. 109.5 degrees
C. 180 degrees
D. 120 degrees
Correct Answer: D
Explanation: Sp2 hybridization results from the mixing of one s and two p orbitals,
creating three hybrid orbitals arranged in a trigonal planar geometry. To minimize electron
repulsion according to VSEPR theory, these orbitals are spaced as far apart as possible. This
arrangement results in ideal bond angles of 120 degrees between the substituents.
6. Identify the functional group present in the molecule CH3CH2OH.
A. Alcohol
B. Ether
C. Ketone
D. Aldehyde
Correct Answer: A
, Explanation: The molecule CH3CH2OH contains a hydroxyl (-OH) group attached to a
saturated carbon atom. This specific arrangement characterizes the alcohol functional
group family. Understanding functional groups is essential for naming compounds and
predicting their chemical reactivity throughout the semester.
7. According to the Brønsted-Lowry definition, what is an acid?
A. A proton (H+) donor.
B. An electron pair acceptor.
C. An electron pair donor.
D. A proton (H+) acceptor.
Correct Answer: A
Explanation: The Brønsted-Lowry theory focuses on the transfer of protons between
species during a chemical reaction. A Brønsted-Lowry acid is defined as any substance that
can donate a hydrogen ion (proton) to another molecule. In contrast, a base is the species
that accepts that proton.
8. Which of the following compounds has the lowest pKa value, indicating it is the strongest
acid?
A. CH4
B. NH3
C. HCl
D. H2O
Correct Answer: C
Explanation: The pKa value is the negative logarithm of the acid dissociation constant
(Ka); thus, lower pKa values correspond to stronger acids. HCl is a strong mineral acid with
a negative pKa, whereas water, ammonia, and methane have much higher pKa values.
Hydrochloric acid completely dissociates in aqueous solution, reflecting its high acidity
compared to the others.
9. When comparing the acidity of HF, HCl, HBr, and HI, which is the strongest acid based on
bond strength and conjugate base stability?
A. HI
B. HCl
C. HBr
D. HF
Correct Answer: A
