CHEM 219 Modules 1–8 Problem Set
(2026/2027) Principles of Organic Chemistry |
Portage Learning – Practice Answer Key
1. How many valence electrons does a carbon atom have?
A) 2
B) 4
C) 6
D) 8
Answer: B) 4
Rationale: Carbon is in Group 14 of the periodic table, meaning it has 4
valence electrons, allowing it to form up to 4 covalent bonds.
2. What is the hybridization of the carbon atom in methane (CH₄)?
A) sp
B) sp²
C) sp³
D) sp³d
Answer: C) sp³
,Rationale: In methane, carbon forms 4 sigma bonds with hydrogen
atoms with no lone pairs. This requires 4 equivalent orbitals, resulting in
sp³ hybridization.
3. What is the molecular geometry of a carbon atom with sp²
hybridization?
A) Linear
B) Trigonal planar
C) Tetrahedral
D) Octahedral
Answer: B) Trigonal planar
Rationale: An sp² hybridized atom has 3 electron domains, resulting in a
trigonal planar geometry with bond angles of approximately 120°.
4. Which of the following best describes a sigma (σ) bond?
A) A bond formed by the side-by-side overlap of p orbitals.
B) A bond formed by the head-on overlap of orbitals.
C) A bond that is weaker than a pi (π) bond.
D) A bond only found in triple bonds.
Answer: B) A bond formed by the head-on overlap of orbitals.
Rationale: Sigma bonds are formed by the direct, head-on overlap of
hybrid or s orbitals, allowing free rotation. They are the strongest type
of covalent bond.
,5. How many pi (π) bonds are present in a carbon-carbon triple bond?
A) 1
B) 2
C) 3
D) 4
Answer: B) 2
Rationale: A triple bond consists of one sigma bond and two pi bonds.
The pi bonds are formed by the side-by-side overlap of unhybridized p
orbitals.
6. What is the formal charge on a nitrogen atom that forms 3 bonds and
has 1 lone pair of electrons?
A) -1
B) 0
C) +1
D) +2
Answer: B) 0
Rationale: Formal charge = (Valence electrons) - (Non-bonding
electrons) - (1/2 Bonding electrons). For nitrogen: 5 - 2 - (1/2 * 6) = 5 - 2
- 3 = 0.
, 7. Which of the following is the most electronegative element?
A) Carbon
B) Nitrogen
C) Oxygen
D) Fluorine
Answer: D) Fluorine
Rationale: Electronegativity increases as you move right and up the
periodic table. Fluorine is the most electronegative element.
8. According to Bronsted-Lowry theory, an acid is a substance that:
A) Accepts a proton (H⁺)
B) Donates a proton (H⁺)
C) Accepts an electron pair
D) Donates an electron pair
Answer: B) Donates a proton (H⁺)
Rationale: Bronsted-Lowry acids are proton donors, while bases are
proton acceptors.
9. Which of the following molecules is the strongest acid?
A) CH₄ (pKa ~50)
B) CH₃OH (pKa ~15.5)
C) CH₃COOH (pKa ~4.75)
(2026/2027) Principles of Organic Chemistry |
Portage Learning – Practice Answer Key
1. How many valence electrons does a carbon atom have?
A) 2
B) 4
C) 6
D) 8
Answer: B) 4
Rationale: Carbon is in Group 14 of the periodic table, meaning it has 4
valence electrons, allowing it to form up to 4 covalent bonds.
2. What is the hybridization of the carbon atom in methane (CH₄)?
A) sp
B) sp²
C) sp³
D) sp³d
Answer: C) sp³
,Rationale: In methane, carbon forms 4 sigma bonds with hydrogen
atoms with no lone pairs. This requires 4 equivalent orbitals, resulting in
sp³ hybridization.
3. What is the molecular geometry of a carbon atom with sp²
hybridization?
A) Linear
B) Trigonal planar
C) Tetrahedral
D) Octahedral
Answer: B) Trigonal planar
Rationale: An sp² hybridized atom has 3 electron domains, resulting in a
trigonal planar geometry with bond angles of approximately 120°.
4. Which of the following best describes a sigma (σ) bond?
A) A bond formed by the side-by-side overlap of p orbitals.
B) A bond formed by the head-on overlap of orbitals.
C) A bond that is weaker than a pi (π) bond.
D) A bond only found in triple bonds.
Answer: B) A bond formed by the head-on overlap of orbitals.
Rationale: Sigma bonds are formed by the direct, head-on overlap of
hybrid or s orbitals, allowing free rotation. They are the strongest type
of covalent bond.
,5. How many pi (π) bonds are present in a carbon-carbon triple bond?
A) 1
B) 2
C) 3
D) 4
Answer: B) 2
Rationale: A triple bond consists of one sigma bond and two pi bonds.
The pi bonds are formed by the side-by-side overlap of unhybridized p
orbitals.
6. What is the formal charge on a nitrogen atom that forms 3 bonds and
has 1 lone pair of electrons?
A) -1
B) 0
C) +1
D) +2
Answer: B) 0
Rationale: Formal charge = (Valence electrons) - (Non-bonding
electrons) - (1/2 Bonding electrons). For nitrogen: 5 - 2 - (1/2 * 6) = 5 - 2
- 3 = 0.
, 7. Which of the following is the most electronegative element?
A) Carbon
B) Nitrogen
C) Oxygen
D) Fluorine
Answer: D) Fluorine
Rationale: Electronegativity increases as you move right and up the
periodic table. Fluorine is the most electronegative element.
8. According to Bronsted-Lowry theory, an acid is a substance that:
A) Accepts a proton (H⁺)
B) Donates a proton (H⁺)
C) Accepts an electron pair
D) Donates an electron pair
Answer: B) Donates a proton (H⁺)
Rationale: Bronsted-Lowry acids are proton donors, while bases are
proton acceptors.
9. Which of the following molecules is the strongest acid?
A) CH₄ (pKa ~50)
B) CH₃OH (pKa ~15.5)
C) CH₃COOH (pKa ~4.75)
