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CHEM 120 CHAMBERLAIN FINAL Actual
Exam 2026/2027 Complete Questions and
Verified Answers with Detailed Rationales
Pass Guaranteed - A+ Graded
Section 1: CHEM 120 Final Exam
Q1: How many protons, neutrons, and electrons are in an atom of ⁴⁰₂₀Ca?
A. 20 protons, 20 neutrons, 40 electrons
B. 40 protons, 20 neutrons, 20 electrons
C. 20 protons, 20 neutrons, 20 electrons [CORRECT]
D. 20 protons, 40 neutrons, 20 electrons
Correct Answer: C
Rationale: The atomic number (20) equals the number of protons and electrons in a neutral atom.
The mass number (40) minus atomic number (20) gives 20 neutrons.
Q2: What is the electron configuration for the ground state of chlorine (Cl, Z=17)?
A. 1s²2s²2p⁶3s²3p⁵ [CORRECT]
B. 1s²2s²2p⁶3s²3p⁶4s¹
C. 1s²2s²2p⁶3s²3p⁴4s¹
D. 1s²2s²2p⁶3s¹3p⁶
Correct Answer: A
Rationale: Following the Aufbau principle, fill orbitals in order of increasing energy: 1s (2e⁻), 2s
(2e⁻), 2p (6e⁻), 3s (2e⁻), 3p (5e⁻) for a total of 17 electrons.
Q3: Which element has the highest first ionization energy?
A. Na
B. Mg
C. Al
D. Cl [CORRECT]
1
,2
Correct Answer: D
Rationale: Ionization energy increases across a period from left to right. Chlorine is furthest right
in period 3, has the smallest atomic radius among these options, and holds its valence electrons
most tightly.
Q4: Calculate the wavelength of light with a frequency of 5.50 × 10¹⁴ Hz. (c = 3.00 × 10⁸ m/s)
A. 545 nm [CORRECT]
B. 5450 nm
C. 1.83 × 10⁶ nm
D. 1.83 × 10⁻⁷ nm
Correct Answer: A
Rationale: Using λ = c/ν = (3.00 × 10⁸ m/s)/(5.50 × 10¹⁴ s⁻¹) = 5.45 × 10⁻⁷ m = 545 nm.
Q5: What are the four quantum numbers for the last electron added to a phosphorus atom
(Z=15)?
A. n=3, l=1, ml=0, ms=+½ [CORRECT]
B. n=3, l=2, ml=1, ms=-½
C. n=2, l=1, ml=0, ms=+½
D. n=3, l=0, ml=0, ms=+½
Correct Answer: A
Rationale: Phosphorus configuration ends in 3p³. The last electron enters the 3p subshell (n=3,
l=1). Following Hund's rule, it occupies ml=0 with spin +½.
Q6: Which ionic compound has the highest lattice energy?
A. NaCl
B. MgO [CORRECT]
C. KBr
D. CaS
Correct Answer: B
Rationale: Lattice energy increases with higher ionic charges and smaller ionic radii. Mg²⁺ and
O²⁻ have the highest charges (+2 and -2) and small radii, creating the strongest electrostatic
attraction.
2
, 3
Q7: How many valence electrons are in the Lewis structure for SO₂?
A. 16
B. 18 [CORRECT]
C. 20
D. 24
Correct Answer: B
Rationale: Sulfur contributes 6 valence electrons and each oxygen contributes 6, totaling 6 + 6 +
6 = 18 valence electrons.
Q8: What is the molecular geometry of NH₃ according to VSEPR theory?
A. Trigonal planar
B. Tetrahedral
C. Trigonal pyramidal [CORRECT]
D. Bent
Correct Answer: C
Rationale: NH₃ has 4 electron domains (3 bonding pairs, 1 lone pair). The electron geometry is
tetrahedral, but with one lone pair, the molecular geometry is trigonal pyramidal with bond
angles of approximately 107°.
Q9: What is the hybridization of the carbon atom in methane (CH₄)?
A. sp
B. sp²
C. sp³ [CORRECT]
D. dsp³
Correct Answer: C
Rationale: Carbon forms 4 sigma bonds with hydrogen atoms, requiring 4 hybrid orbitals. One s
orbital and three p orbitals hybridize to form four equivalent sp³ hybrid orbitals arranged
tetrahedrally.
Q10: Calculate the molar mass of Ca(NO₃)₂.
A. 102 g/mol
B. 164 g/mol [CORRECT]
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CHEM 120 CHAMBERLAIN FINAL Actual
Exam 2026/2027 Complete Questions and
Verified Answers with Detailed Rationales
Pass Guaranteed - A+ Graded
Section 1: CHEM 120 Final Exam
Q1: How many protons, neutrons, and electrons are in an atom of ⁴⁰₂₀Ca?
A. 20 protons, 20 neutrons, 40 electrons
B. 40 protons, 20 neutrons, 20 electrons
C. 20 protons, 20 neutrons, 20 electrons [CORRECT]
D. 20 protons, 40 neutrons, 20 electrons
Correct Answer: C
Rationale: The atomic number (20) equals the number of protons and electrons in a neutral atom.
The mass number (40) minus atomic number (20) gives 20 neutrons.
Q2: What is the electron configuration for the ground state of chlorine (Cl, Z=17)?
A. 1s²2s²2p⁶3s²3p⁵ [CORRECT]
B. 1s²2s²2p⁶3s²3p⁶4s¹
C. 1s²2s²2p⁶3s²3p⁴4s¹
D. 1s²2s²2p⁶3s¹3p⁶
Correct Answer: A
Rationale: Following the Aufbau principle, fill orbitals in order of increasing energy: 1s (2e⁻), 2s
(2e⁻), 2p (6e⁻), 3s (2e⁻), 3p (5e⁻) for a total of 17 electrons.
Q3: Which element has the highest first ionization energy?
A. Na
B. Mg
C. Al
D. Cl [CORRECT]
1
,2
Correct Answer: D
Rationale: Ionization energy increases across a period from left to right. Chlorine is furthest right
in period 3, has the smallest atomic radius among these options, and holds its valence electrons
most tightly.
Q4: Calculate the wavelength of light with a frequency of 5.50 × 10¹⁴ Hz. (c = 3.00 × 10⁸ m/s)
A. 545 nm [CORRECT]
B. 5450 nm
C. 1.83 × 10⁶ nm
D. 1.83 × 10⁻⁷ nm
Correct Answer: A
Rationale: Using λ = c/ν = (3.00 × 10⁸ m/s)/(5.50 × 10¹⁴ s⁻¹) = 5.45 × 10⁻⁷ m = 545 nm.
Q5: What are the four quantum numbers for the last electron added to a phosphorus atom
(Z=15)?
A. n=3, l=1, ml=0, ms=+½ [CORRECT]
B. n=3, l=2, ml=1, ms=-½
C. n=2, l=1, ml=0, ms=+½
D. n=3, l=0, ml=0, ms=+½
Correct Answer: A
Rationale: Phosphorus configuration ends in 3p³. The last electron enters the 3p subshell (n=3,
l=1). Following Hund's rule, it occupies ml=0 with spin +½.
Q6: Which ionic compound has the highest lattice energy?
A. NaCl
B. MgO [CORRECT]
C. KBr
D. CaS
Correct Answer: B
Rationale: Lattice energy increases with higher ionic charges and smaller ionic radii. Mg²⁺ and
O²⁻ have the highest charges (+2 and -2) and small radii, creating the strongest electrostatic
attraction.
2
, 3
Q7: How many valence electrons are in the Lewis structure for SO₂?
A. 16
B. 18 [CORRECT]
C. 20
D. 24
Correct Answer: B
Rationale: Sulfur contributes 6 valence electrons and each oxygen contributes 6, totaling 6 + 6 +
6 = 18 valence electrons.
Q8: What is the molecular geometry of NH₃ according to VSEPR theory?
A. Trigonal planar
B. Tetrahedral
C. Trigonal pyramidal [CORRECT]
D. Bent
Correct Answer: C
Rationale: NH₃ has 4 electron domains (3 bonding pairs, 1 lone pair). The electron geometry is
tetrahedral, but with one lone pair, the molecular geometry is trigonal pyramidal with bond
angles of approximately 107°.
Q9: What is the hybridization of the carbon atom in methane (CH₄)?
A. sp
B. sp²
C. sp³ [CORRECT]
D. dsp³
Correct Answer: C
Rationale: Carbon forms 4 sigma bonds with hydrogen atoms, requiring 4 hybrid orbitals. One s
orbital and three p orbitals hybridize to form four equivalent sp³ hybrid orbitals arranged
tetrahedrally.
Q10: Calculate the molar mass of Ca(NO₃)₂.
A. 102 g/mol
B. 164 g/mol [CORRECT]
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