Gaseous State of Matter — A/L Chemistry

How do I practise Gaseous State of Matter?

1 question with a worked solution

Check before you answer: Dalton's Law of Partial Pressures: Using mole fraction (P_A = x_A × P_total) to determine partial pressures of gas mixtures collected over water (subtracting saturated vapor pressure).

1. A rigid closed vessel contains 4.0 g of methane (CH₄, molar mass = 16.0 g mol⁻¹) and 28.0 g of nitrogen (N₂, molar mass = 28.0 g mol⁻¹) at 300 K. If the total pressure in the vessel is 1.50 atm, what is the partial pressure of methane?
   1. A) 0.25 atm
   2. B) 0.30 atm
   3. C) 0.75 atm
   4. D) 1.20 atm
   Check my answer

   Correct answer: B) 0.30 atm

   According to Dalton's Law of Partial Pressures, P_i = x_i × P_total. Moles of CH₄ = 4.0 / 16.0 = 0.25 mol. Moles of N₂ = 28.0 / 28.0 = 1.00 mol. Total moles = 0.25 + 1.00 = 1.25 mol. Mole fraction of CH₄ = 0.25 / 1.25 = 0.20. Therefore, P(CH₄) = 0.20 × 1.50 atm = 0.30 atm.

   Show worked solution

   Step 1: Calculate moles of each component: n(CH₄) = 4.0 g / 16.0 g mol⁻¹ = 0.25 mol n(N₂) = 28.0 g / 28.0 g mol⁻¹ = 1.00 mol Step 2: Calculate total moles: n_total = 0.25 + 1.00 = 1.25 mol. Step 3: Calculate mole fraction of methane: x(CH₄) = n(CH₄) / n_total = 0.25 / 1.25 = 0.20. Step 4: Apply Dalton's law: P(CH₄) = x(CH₄) × P_total = 0.20 × 1.50 atm = 0.30 atm. Answer: 0.30 atm.
   Modelled on: the A/L Chemistry examination pattern

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Where does Gaseous State of Matter fit in the syllabus?

Grade 12 · Term 2