Daltons Law of Partial Pressures - UNSOLVED PRACTICE SET
Chapter: States of Matter | Topic: Daltons Law of Partial Pressures
DALTONS LAW OF PARTIAL PRESSURES - UNSOLVED PRACTICE SET
Topic: Daltons Law of Partial Pressures
Multiple Choice Questions
Q1. Dalton's Law of Partial Pressures states that the total pressure of a mixture of gases is:
- Equal to the pressure of the most abundant gas
- Equal to the sum of the partial pressures of individual gases
- Equal to the average of the partial pressures
- Equal to the product of the partial pressures
Q2. The partial pressure of a gas in a mixture is given by:
- Pi = Xi × Ptotal
- Pi = Ptotal/Xi
- Pi = Xi/Ptotal
- Pi = Xi + Ptotal
Q3. The mole fraction of a gas in a mixture is defined as:
- Moles of the gas / Total moles of all gases
- Total moles / Moles of the gas
- Mass of the gas / Total mass
- Volume of the gas / Total volume
Q4. A mixture contains 2 moles of N₂ and 3 moles of O₂. The mole fraction of N₂ is:
- 0.2
- 0.4
- 0.6
- 0.8
Q5. At constant temperature and volume, the partial pressure of a gas is proportional to:
- Its molar mass
- Its number of moles
- Its density
- Its volume
Q6. The total pressure of a gas mixture containing 0.5 mol He, 1.0 mol Ne, and 1.5 mol Ar at constant V and T is 4.0 atm. The partial pressure of Ne is:
- 0.5 atm
- 1.0 atm
- 1.33 atm
- 2.0 atm
Short Answer Questions
Q7. State Dalton's Law of Partial Pressures. Write its mathematical expression for a mixture of three gases.
Q8. Define mole fraction. Write the relationship between mole fraction and partial pressure of a gas in a mixture.
Q9. A mixture of gases contains 2.0 g H₂ and 8.0 g O₂. Calculate the mole fraction of each gas.
Q10. Explain why the partial pressure of a gas in a mixture depends only on its number of moles, and not on the presence of other gases.
Q11. A container holds a mixture of N₂ and O₂ at a total pressure of 1.0 atm. If the partial pressure of N₂ is 0.7 atm, what is the partial pressure of O₂?
Q12. State and explain the relationship between partial pressure and mole fraction. Why is this relationship valid only for ideal gases?
Long Answer Questions
Q13. (a) State and explain Dalton's Law of Partial Pressures with a suitable example.
(b) A mixture contains 4.0 g of CH₄ and 8.0 g of O₂ in a 10.0 L container at 300 K. Calculate:
(i) The mole fraction of each gas
(ii) The partial pressure of each gas
(iii) The total pressure of the mixture
(R = 0.0821 L·atm/mol·K)
Q14. (a) Derive the relationship between partial pressure and mole fraction: Pi = Xi × Ptotal.
(b) A gaseous mixture contains 20% N₂, 30% O₂, and 50% CO₂ by volume. If the total pressure is 2.0 atm, calculate the partial pressure of each gas.
(c) Explain why, at the same temperature and pressure, the volume percent of a gas is equal to its mole percent.
Q15. (a) Explain the application of Dalton's Law in:
(i) Collecting gases over water
(ii) Determining the pressure of dry gas
(b) A gas is collected over water at 25°C. The total pressure is 755 mmHg and the vapour pressure of water at 25°C is 23.8 mmHg. Calculate the pressure of the dry gas.
(c) Why is it necessary to correct for the vapour pressure of water when a gas is collected by displacement of water?
Numerical / Application-Based Problems
Q16. A 5.0 L vessel contains a mixture of 0.2 mol N₂, 0.3 mol O₂, and 0.5 mol CO₂ at 300 K.
(a) Calculate the mole fraction of each gas.
(b) Calculate the partial pressure of each gas.
(c) Calculate the total pressure of the mixture.
(d) If 0.2 mol of N₂ is removed from the vessel at constant temperature, calculate the new total pressure and the new partial pressure of each remaining gas.
(R = 0.0821 L·atm/mol·K)
Q17. A student collects hydrogen gas by the downward displacement of water:
(a) 0.20 g of magnesium reacts with excess dilute HCl. Calculate the moles of H₂ produced. (M of Mg = 24 g/mol)
(b) The gas is collected over water at 25°C. The total pressure is 750 mmHg and the aqueous tension at 25°C is 23.8 mmHg. Calculate the pressure of dry H₂.
(c) If the volume of gas collected is 220 mL, calculate the temperature of the experiment. (R = 0.0821 L·atm/mol·K)
(d) The student forgets to correct for aqueous tension and calculates the molar volume incorrectly. Calculate the percentage error introduced by this mistake.
Q18. In India, Dalton's Law has practical applications in various fields:
(a) Scuba divers use a mixture of N₂ and O₂ (and sometimes He) for breathing underwater. A diving tank contains 32% O₂ and 68% N₂ by moles at a total pressure of 200 atm. Calculate the partial pressure of each gas. Why is pure oxygen not used for deep-sea diving?
(b) In a hospital, an oxygen cylinder contains a mixture of O₂ and N₂. The partial pressure of O₂ is 3.0 atm and that of N₂ is 2.0 atm. Calculate the total pressure and the mole fraction of O₂ in the cylinder.
(c) LPG (liquefied petroleum gas) used in Indian households is mainly a mixture of propane and butane. If a cylinder contains 60% propane and 40% butane by moles at a total pressure of 5.0 atm, calculate the partial pressure of each component.
(d) In the steel industry, a mixture of CO and CO₂ is used in blast furnaces. A gas sample contains 2.0 mol CO and 3.0 mol CO₂ at a total pressure of 10.0 atm. Calculate the partial pressure of CO. Explain how this partial pressure affects the reduction of iron oxide in the furnace.