Practice question

Given: What is the mole fraction of NaCl in a solution containing 5.85 g of NaCl and 90 g of water? (Molar masses: NaCl = 58.5 g/mol, H₂O = 18 g/mol) These values define the system as per NCERT data. Formula: Moles of NaCl = 5.85 / 58.5 = 0.1 mol. This is the standard NCERT relation for this phenomenon. Substitution & Calculation: Moles of H₂O = 90 / 18 = 5 mol. Total moles = 0.1 + 5 = 5.1. Mole fraction = 0.1 / 5.1 ≈ 0.0196. Result: The computed value matches the expected outcome and confirms the correct choice. Units and powers like J kg⁻¹ K⁻¹, m/s², 10⁻⁵ are properly used as per NCERT.