Practice question

Given: A solution of 2.44 g of acetic acid ( CH₃COOH ) in 100 g of benzene shows a freezing point depression of 0.5 K. If the molar mass is 60 g/mol, what is the van't Hoff factor due to dimerization? ( K_f = 5.12 K kg/mol ) These values define the system as per NCERT data. Formula: Molality = 2.44 / 60/0.1 = 0.4067 mol/kg. This is the standard NCERT relation for this phenomenon. Substitution & Calculation: Normal Δ T_f = 5.12 × 0.4067 = 2.08 K . Observed Δ T_f = 0.5 K . i = 0.5/2.08 = 0.24 . 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.