A mixture of solid P₄ and gaseous O₂ contains a total of 3.0 moles. The mixture is allowed to react completely to form P₄O₁₀ . If 71.0 g of P₄O₁₀ is formed and O₂ is completely consumed in the reaction, what is the mass of the unreacted P₄ left? [Given: Molar atomic mass in g mol ⁻¹ : P = 31 , O = 16 ]

Step-by-step solution

The balanced chemical equation is: P₄(s) + 5O₂(g) P₄O₁₀(s) Molar mass of P₄O₁₀ = 4 31 + 10 16 = 124 + 160 = 284 g mol ⁻¹ . Moles of P₄O₁₀ formed = 71.0 284 = 0.25 mol . From the stoichiometry, 1 mol of P₄O₁₀ requires 5 mol of O₂ and 1 mol of P₄ . Moles of O₂ reacted = 0.25 5 = 1.25 mol . Moles of P₄ reacted = 0.25 1 = 0.25 mol . Since O₂ is completely consumed, the initial moles of O₂ = 1.25 mol . Total initial moles in the mixture = 3.0 mol . Initial moles of P₄ = 3.0 - 1.25 = 1.75 mol . Moles of unreacted P₄ = 1.