A gaseous mixture of O ₂ and CH ₄ is prepared such that it contains 20 % by mass of CH ₄ . The total pressure of the mixture in a container is 60 bar . Find the partial pressure of O ₂ in bar. [Given: Molar mass of O ₂ = 32 g mol ⁻¹ , Molar mass of CH ₄ = 16 g mol ⁻¹ ]

Step-by-step solution

Let the total mass of the gaseous mixture be 100 g . Mass of CH ₄ = 20 g Mass of O ₂ = 80 g Number of moles of CH ₄ , n_ CH ₄ = 20 16 = 1.25 mol Number of moles of O ₂ , n_ O ₂ = 80 32 = 2.5 mol Total number of moles = 1.25 + 2.5 = 3.75 mol Mole fraction of O ₂ , X_ O ₂ = 2.5 3.75 = 2 3 According to Dalton's Law of Partial Pressures: P_ O ₂ = X_ O ₂ P_ total P_ O ₂ = 2 3 60 = 40 bar Answer: 40