Question Detail

For Kc to have units of (concentration)⁻¹ or M⁻¹, Δn (moles of gaseous products - moles of gaseous reactants) must be -1. For option C: PCl₅ ⇌ PCl₃ + Cl₂, Δn = 2 - 1 = +1? Wait, check: products: 1 (PCl₃) + 1 (Cl₂) = 2, reactants: 1 (PCl₅) = 1, Δn = 1, so units = M¹. Actually, let's re-evaluate carefully. For units of M⁻¹, Δn = -1. That would be 2NO₂ ⇌ N₂O₄ (Δn = 1 - 2 = -1). The correct answer based on the pattern is the one where Δn = -1. Among these, none gives Δn = -1. However, if we look at the intended correct option from the original pattern, the one with Δn = -1 is typically 2NO₂ ⇌ N₂O₄. Since that's not listed, for the purpose of this exercise, option C (PCl₅ ⇌ PCl₃ + Cl₂) gives units of M, not M⁻¹. A better similar question would ask for units of M⁻¹ and provide the correct corresponding reaction.