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ZUMDAHL CHEMISTRY EXAM PACK 2026 QUESTIONS
WITH VERIFIED ANSWERS DETAILED RATIONALES
GRADED A+
Zumdahl Chemistry (9th Edition)
SECTION 1: CHEMICAL FOUNDATIONS (Questions 1–15)
1. Which of the following is a fundamental SI unit?
A) Gram
B) Liter
C) Kelvin
D) Pound
Answer: C) Kelvin
Rationale: The kelvin (K) is the SI base unit of thermodynamic temperature. The gram is a unit
of mass (the SI base unit is the kilogram), the liter is a unit of volume (the SI base unit is the
cubic meter), and the pound is an imperial unit.
2. How many significant figures are in the measurement 0.0045020 g?
A) 4
B) 5
C) 6
D) 7
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Answer: B) 5
Rationale: Leading zeros (0.00) are not significant. The digits 4, 5, 0, 2, and the trailing 0 after
the decimal point are significant. Therefore, there are 5 significant figures.
3. Express 0.0000456 in scientific notation.
A) 4.56 × 10⁻⁵
B) 4.56 × 10⁵
C) 45.6 × 10⁻⁶
D) 0.456 × 10⁻⁴
Answer: A) 4.56 × 10⁻⁵
Rationale: Move the decimal point 5 places to the right to get 4.56, so the exponent is −5.
4. How many moles of atoms are in 12.0 g of carbon? (Molar mass of C = 12.01 g/mol)
A) 0.999 mol
B) 1.00 mol
C) 12.0 mol
D) 144 mol
Answer: B) 1.00 mol
Rationale: moles = mass / molar mass = 12.0 g / 12.01 g/mol ≈ 0.999 mol, which rounds to 1.00
mol to three significant figures.
5. How many molecules are in 2.50 mol of H₂O?
A) 2.50 × 10²³
B) 1.51 × 10²⁴
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C) 6.02 × 10²³
D) 4.15 × 10²⁴
Answer: B) 1.51 × 10²⁴
Rationale: Number of molecules = moles × Avogadro's number = 2.50 mol × 6.022 × 10²³
molecules/mol = 1.51 × 10²⁴ molecules.
6. What is the mass of 3.01 × 10²³ atoms of sodium? (Molar mass Na = 22.99 g/mol)
A) 11.5 g
B) 22.99 g
C) 5.75 g
D) 3.01 g
Answer: A) 11.5 g
Rationale: moles = 3.01 × 10²³ / 6.022 × 10²³ = 0.500 mol. Mass = 0.500 mol × 22.99 g/mol =
11.5 g.
7. What is the empirical formula of a compound that is 40.0% C, 6.71% H, and 53.3% O by
mass?
A) CH₂O
B) C₂H₄O₂
C) CHO
D) C₂H₂O
Answer: A) CH₂O
Rationale: Assume 100 g: 40.0 g C (3.33 mol), 6.71 g H (6.66 mol), 53.3 g O (3.33 mol). Divide by
3.33: C₁H₂O₁ → CH₂O.
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8. A compound has an empirical formula of CH₂ and a molar mass of 42.08 g/mol. What is its
molecular formula?
A) CH₂
B) C₂H₄
C) C₃H₆
D) C₄H₈
Answer: C) C₃H₆
Rationale: Empirical formula mass = 14.03 g/mol. n = 42..03 ≈ 3. Molecular formula =
(CH₂)₃ = C₃H₆.
9. Balance the equation: __ C₃H₈ + __ O₂ → __ CO₂ + __ H₂O
A) 1, 5, 3, 4
B) 2, 10, 6, 8
C) 1, 3, 3, 4
D) 2, 7, 6, 8
Answer: A) 1, 5, 3, 4
Rationale: C₃H₈ + 5 O₂ → 3 CO₂ + 4 H₂O. Carbon: 3 = 3. Hydrogen: 8 = 8. Oxygen: 10 = 6 + 4 = 10.
10. In the reaction 2 H₂ + O₂ → 2 H₂O, if 4.0 mol H₂ reacts with excess O₂, how many moles of
H₂O are produced?
A) 2.0 mol
B) 4.0 mol
C) 8.0 mol
D) 1.0 mol
Answer: B) 4.0 mol
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ZUMDAHL CHEMISTRY EXAM PACK 2026 QUESTIONS
WITH VERIFIED ANSWERS DETAILED RATIONALES
GRADED A+
Zumdahl Chemistry (9th Edition)
SECTION 1: CHEMICAL FOUNDATIONS (Questions 1–15)
1. Which of the following is a fundamental SI unit?
A) Gram
B) Liter
C) Kelvin
D) Pound
Answer: C) Kelvin
Rationale: The kelvin (K) is the SI base unit of thermodynamic temperature. The gram is a unit
of mass (the SI base unit is the kilogram), the liter is a unit of volume (the SI base unit is the
cubic meter), and the pound is an imperial unit.
2. How many significant figures are in the measurement 0.0045020 g?
A) 4
B) 5
C) 6
D) 7
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Answer: B) 5
Rationale: Leading zeros (0.00) are not significant. The digits 4, 5, 0, 2, and the trailing 0 after
the decimal point are significant. Therefore, there are 5 significant figures.
3. Express 0.0000456 in scientific notation.
A) 4.56 × 10⁻⁵
B) 4.56 × 10⁵
C) 45.6 × 10⁻⁶
D) 0.456 × 10⁻⁴
Answer: A) 4.56 × 10⁻⁵
Rationale: Move the decimal point 5 places to the right to get 4.56, so the exponent is −5.
4. How many moles of atoms are in 12.0 g of carbon? (Molar mass of C = 12.01 g/mol)
A) 0.999 mol
B) 1.00 mol
C) 12.0 mol
D) 144 mol
Answer: B) 1.00 mol
Rationale: moles = mass / molar mass = 12.0 g / 12.01 g/mol ≈ 0.999 mol, which rounds to 1.00
mol to three significant figures.
5. How many molecules are in 2.50 mol of H₂O?
A) 2.50 × 10²³
B) 1.51 × 10²⁴
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C) 6.02 × 10²³
D) 4.15 × 10²⁴
Answer: B) 1.51 × 10²⁴
Rationale: Number of molecules = moles × Avogadro's number = 2.50 mol × 6.022 × 10²³
molecules/mol = 1.51 × 10²⁴ molecules.
6. What is the mass of 3.01 × 10²³ atoms of sodium? (Molar mass Na = 22.99 g/mol)
A) 11.5 g
B) 22.99 g
C) 5.75 g
D) 3.01 g
Answer: A) 11.5 g
Rationale: moles = 3.01 × 10²³ / 6.022 × 10²³ = 0.500 mol. Mass = 0.500 mol × 22.99 g/mol =
11.5 g.
7. What is the empirical formula of a compound that is 40.0% C, 6.71% H, and 53.3% O by
mass?
A) CH₂O
B) C₂H₄O₂
C) CHO
D) C₂H₂O
Answer: A) CH₂O
Rationale: Assume 100 g: 40.0 g C (3.33 mol), 6.71 g H (6.66 mol), 53.3 g O (3.33 mol). Divide by
3.33: C₁H₂O₁ → CH₂O.
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8. A compound has an empirical formula of CH₂ and a molar mass of 42.08 g/mol. What is its
molecular formula?
A) CH₂
B) C₂H₄
C) C₃H₆
D) C₄H₈
Answer: C) C₃H₆
Rationale: Empirical formula mass = 14.03 g/mol. n = 42..03 ≈ 3. Molecular formula =
(CH₂)₃ = C₃H₆.
9. Balance the equation: __ C₃H₈ + __ O₂ → __ CO₂ + __ H₂O
A) 1, 5, 3, 4
B) 2, 10, 6, 8
C) 1, 3, 3, 4
D) 2, 7, 6, 8
Answer: A) 1, 5, 3, 4
Rationale: C₃H₈ + 5 O₂ → 3 CO₂ + 4 H₂O. Carbon: 3 = 3. Hydrogen: 8 = 8. Oxygen: 10 = 6 + 4 = 10.
10. In the reaction 2 H₂ + O₂ → 2 H₂O, if 4.0 mol H₂ reacts with excess O₂, how many moles of
H₂O are produced?
A) 2.0 mol
B) 4.0 mol
C) 8.0 mol
D) 1.0 mol
Answer: B) 4.0 mol
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