Questions on Dalton’s Law of Partial Pressures
Dalton’s Law of Partial Pressures – Multiple Choice Questions
1. What does Dalton’s Law state?
A) The pressure of a gas is inversely proportional to its volume.
B) Total pressure equals the product of all individual gas pressures.
C) Total pressure of a mixture equals the sum of individual gas pressures.
D) Partial pressure is irrelevant in gas mixtures.
E) The heavier gas exerts more pressure.
2. Dalton’s Law applies to which kind of gas mixtures?
A) Only pure gases
B) Gases under high pressure
C) Ideal gases in a mixture
D) Liquids
E) Gases at absolute zero
3. What is a partial pressure?
A) The total pressure divided by volume
B) The pressure exerted by one gas in a mixture
C) Pressure caused by solid particles
D) Atmospheric pressure
E) Difference between pressures in two containers
4. What is the formula for Dalton’s Law?
A) P₁ × V = P₂ × V
B) P = nRT/V
C) P_total = P₁ + P₂ + P₃ + …
D) P_total = RT/V
E) P_total = P₁/P₂
5. A gas mixture contains three gases with pressures 2 atm, 3 atm, and 5 atm. What is the total pressure?
A) 6 atm
B) 8 atm
C) 10 atm
D) 9 atm
E) 12 atm
6. A mixture contains nitrogen (2 atm), oxygen (1 atm), and helium (0.5 atm). What is the partial pressure of oxygen?
A) 3.5 atm
B) 0.5 atm
C) 1 atm
D) 2 atm
E) 1.5 atm
7. The total pressure of a gas mixture is 1 atm. If gas A exerts 0.4 atm and gas B exerts 0.3 atm, what is the partial pressure of gas C?
A) 0.3 atm
B) 0.7 atm
C) 0.4 atm
D) 0.6 atm
E) 0.2 atm
8. Which variable is not involved in Dalton’s Law?
A) Volume
B) Total pressure
C) Partial pressures
D) Types of gases
E) None of the above
9. Dalton's Law is most accurate under which conditions?
A) High temperature, low pressure
B) High pressure, low temperature
C) At boiling point
D) In solids
E) When gases react chemically
10. According to Dalton’s Law, each gas in a mixture acts:
A) Independently and contributes its own pressure
B) By increasing the pressure of other gases
C) By reducing the total volume
D) As if it were a liquid
E) Dependent on molecular weight
11. If the mole fraction of gas A is 0.25 and the total pressure is 800 mmHg, what is the partial pressure of gas A?
A) 800 mmHg
B) 200 mmHg
C) 600 mmHg
D) 0.25 mmHg
E) 100 mmHg
12. How is partial pressure related to mole fraction?
A) Pₐ = Xₐ × P_total
B) Pₐ = Xₐ + P_total
C) Pₐ = P_total / Xₐ
D) Pₐ = Xₐ - P_total
E) Pₐ = P_total × V
13. Which of the following gases would exert the same partial pressure if equal moles are present at same temperature and volume?
A) He and O₂
B) CO₂ and H₂O
C) N₂ and CO
D) CH₄ and NH₃
E) All of the above
14. Which of the following increases the total pressure of a gas mixture?
A) Decreasing volume
B) Removing gas
C) Lowering temperature
D) Adding a vacuum
E) Reducing moles of gas
15. Dalton’s Law is useful in calculating:
A) Boiling points
B) Gas solubility in liquids
C) Pressure of individual gases in mixtures
D) Melting points
E) Acid strength
16. What is the unit for partial pressure?
A) Kelvin
B) Liters
C) Moles
D) Atmospheres or mmHg
E) Newtons
17. If a gas mixture contains equal moles of N₂, O₂, and CO₂, which gas has the highest partial pressure?
A) N₂
B) O₂
C) CO₂
D) All the same
E) Depends on molecular mass
18. If the total pressure is 900 torr and a gas has a mole fraction of 0.60, what is its partial pressure?
A) 540 torr
B) 360 torr
C) 600 torr
D) 300 torr
E) 720 torr
19. What assumption is essential for Dalton’s Law?
A) Gases react with each other
B) Gases behave ideally
C) Gases have strong intermolecular forces
D) Pressure is not measurable
E) Gases are liquids
20. Which of the following scenarios violates Dalton’s Law?
A) Non-reactive gas mixture
B) High-pressure reactive gas mixture
C) Low-pressure ideal gases
D) Mixing air with helium
E) Gases in separate containers
Answers with Full Explanations
1. C – Dalton’s Law says that the total pressure is the sum of the partial pressures of all gases.
2. C – It applies to ideal gas mixtures, where gases behave independently.
3. B – Partial pressure is the pressure exerted by one component of a gas mixture.
4. C – The formula is P_total = P₁ + P₂ + P₃ + …
5. C – Total = 2 + 3 + 5 = 10 atm
6. C – Oxygen’s partial pressure is given as 1 atm
7. A – Total = 1 atm, known gases = 0.4 + 0.3 = 0.7; C = 0.3 atm
8. A – Dalton’s Law doesn’t depend on volume, only on pressure.
9. A – It works best at high temperature and low pressure, where gases are ideal.
10. A – Each gas behaves independently, exerting pressure as if alone.
11. B – Pₐ = Xₐ × P_total = 0.25 × 800 = 200 mmHg
12. A – The correct formula: Pₐ = Xₐ × P_total
13. E – If moles, T, and V are the same, all gases exert equal partial pressure
14. A – Decreasing volume increases pressure (Boyle’s Law also applies).
15. C – Dalton’s Law is about individual gas pressures in mixtures.
16. D – Pressure is measured in atm or mmHg.
17. D – Equal moles = equal partial pressures at constant T and V.
18. A – P = 0.60 × 900 = 540 torr
19. B – Dalton’s Law assumes ideal gas behavior (no interactions).
20. B – Reactive gases at high pressure can form new substances, violating Dalton’s Law.
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