Practice question

Given: Calculate the mole fraction of ethanol ( C₂H₅OH ) in a solution containing 69 g of ethanol and 198 g of water. (Molar mass: C₂H₅OH = 46 g/mol, H₂O = 18 g/mol ) These values define the system as per NCERT data. Formula: Moles of ethanol = 69/46 = 1.5 mol. This is the standard NCERT relation for this phenomenon. Substitution & Calculation: Moles of water = 198/18 = 11 mol . Total moles = 1.5 + 11 = 12.5. Mole fraction of ethanol = 1.5/12.5 = 0.12 . 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.