Questions on Avogadro’s Number
Multiple-Choice Questions: Avogadro’s Number
1. What is Avogadro’s number?
A) 6.02 × 10¹⁹
B) 3.01 × 10²³
C) 1.00 × 10²⁴
D) 6.02 × 10²³
E) 6.02 × 10²⁶
2. Avogadro’s number represents the number of particles in:
A) 1 gram of any substance
B) 1 mole of a substance
C) 1 liter of water
D) 1 molecule of gas
E) 1 mole of atoms only
3. Which of the following has approximately 6.02 × 10²³ molecules?
A) 1 gram of H₂O
B) 1 mole of CO₂
C) 1 mL of O₂
D) 1 molecule of CH₄
E) 1 mole of electrons
4. Avogadro’s number is used to convert between:
A) Grams and liters
B) Moles and atoms/molecules
C) Degrees and radians
D) Liters and temperature
E) Kilograms and moles
5. Which quantity contains the greatest number of particles?
A) 1 mole of water
B) 18 grams of water
C) 1 mole of sodium
D) 6.02 × 10²³ oxygen molecules
E) All of the above
6. How many atoms are in 2 moles of helium?
A) 3.01 × 10²³
B) 6.02 × 10²³
C) 1.20 × 10²⁴
D) 2.00 × 10²⁶
E) 3.01 × 10²⁶
7. One mole of NaCl contains how many formula units?
A) 6.02
B) 6.02 × 10²³
C) 3.01 × 10²³
D) 1.00 × 10⁶
E) 1.00 × 10²³
8. How many oxygen atoms are in one mole of O₂?
A) 6.02 × 10²³
B) 1.20 × 10²⁴
C) 3.01 × 10²³
D) 6.02
E) 1.00 × 10²⁴
9. Avogadro’s number is named after which scientist?
A) Antoine Lavoisier
B) Amedeo Avogadro
C) John Dalton
D) Dmitri Mendeleev
E) Marie Curie
10. Which of the following has the fewest number of molecules?
A) 0.5 mol of CO₂
B) 1 mol of H₂O
C) 0.25 mol of O₂
D) 0.75 mol of CH₄
E) 1 mol of NH₃
11. How many particles are in 0.25 mol of a substance?
A) 1.51 × 10²³
B) 2.41 × 10²²
C) 3.01 × 10²³
D) 1.20 × 10²⁴
E) 2.50 × 10²²
12. Which of the following statements is TRUE about 1 mole of a substance?
A) It weighs 1 gram
B) It contains 1.00 × 10²⁴ particles
C) It contains 6.02 × 10²³ representative particles
D) It contains 6.02 × 10²⁶ atoms
E) It is equal to 1 liter
13. Which of the following quantities is equal to Avogadro’s number?
A) Atoms in 1 mole of iron
B) Molecules in 1 mole of water
C) Ions in 1 mole of NaCl
D) All of the above
E) None of the above
14. What is the number of hydrogen atoms in 1 mole of H₂O?
A) 6.02 × 10²³
B) 1.20 × 10²⁴
C) 3.01 × 10²³
D) 2.00 × 10²⁴
E) 2.00 × 10²³
15. Which is the correct use of Avogadro’s number?
A) To find the number of atoms in a molecule
B) To calculate atomic mass
C) To convert between mass and volume
D) To convert moles to number of particles
E) To find the molar volume of gases
16. If you have 3.01 × 10²³ molecules of CO₂, how many moles do you have?
A) 0.25
B) 0.50
C) 1.00
D) 2.00
E) 0.75
17. Which of the following contains the greatest number of atoms?
A) 1 mole of CH₄
B) 1 mole of O₂
C) 1 mole of NaCl
D) 1 mole of HCl
E) 1 mole of CO₂
18. How many formula units are in 0.75 mol of NaCl?
A) 3.01 × 10²³
B) 4.52 × 10²³
C) 6.02 × 10²³
D) 1.51 × 10²³
E) 1.20 × 10²⁴
19. Avogadro’s number allows chemists to:
A) Predict electron configurations
B) Balance chemical equations
C) Count particles in a given amount of substance
D) Determine density
E) Identify isotopes
20. If 1 mol of oxygen gas (O₂) is present, how many oxygen atoms are there?
A) 6.02 × 10²³
B) 3.01 × 10²³
C) 1.20 × 10²⁴
D) 2.00 × 10²³
E) 2.00 × 10²²
Answers and Explanations
1. D) 6.02 × 10²³ — This is the defined value of Avogadro’s number.
2. B) 1 mole of a substance — Avogadro’s number is the number of particles in a mole.
3. B) 1 mole of CO₂ — 1 mole always contains 6.02 × 10²³ entities.
4. B) Moles and atoms/molecules — Avogadro’s number bridges this conversion.
5. E) All of the above — Each quantity equals 1 mole, thus the same number of particles.
6. C) 1.20 × 10²⁴ — 2 moles × 6.02 × 10²³ = 1.204 × 10²⁴
7. B) 6.02 × 10²³ — 1 mole = Avogadro’s number of units.
8. B) 1.20 × 10²⁴ — 1 mole of O₂ has 2 atoms per molecule: 2 × 6.02 × 10²³
9. B) Amedeo Avogadro — He hypothesized the concept that led to this number.
10. C) 0.25 mol of O₂ — It has the fewest moles, hence fewest molecules.
11. A) 1.51 × 10²³ — 0.25 mol × 6.02 × 10²³ = 1.505 × 10²³
12. C) It contains 6.02 × 10²³ representative particles — By definition.
13. D) All of the above — 1 mole of any substance = 6.02 × 10²³ particles.
14. B) 1.20 × 10²⁴ — 2 H atoms per H₂O molecule × 6.02 × 10²³
15. D) To convert moles to number of particles — This is its main function.
16. B) 0.50 — (3.01 × 10²³) ÷ (6.02 × 10²³) = 0.5 mol
17. A) 1 mole of CH₄ — 5 atoms per molecule × 6.02 × 10²³ = most atoms
18. B) 0.75 × 6.02 × 10²³ = 4.515 × 10²³
19. C) Count particles in a given amount of substance — Primary use.
20. C) 1.20 × 10²⁴ — Each O₂ molecule has 2 oxygen atoms × 6.02 × 10²³
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