Practice question

Given: How many grams of ethylene glycol ( C₂H₆O₂ ) are required to depress the freezing point of 300 g of water by 1.24 K? ( K_f = 1.86 K kg/mol, Molar mass of ethylene glycol = 62 g/mol ) These values define the system as per NCERT data. Formula: Δ T_f = K_f · m. This is the standard NCERT relation for this phenomenon. Substitution & Calculation: 1.24 = 1.86 · m, m = 0.667 mol/kg . Moles = 0.667 × 0.3 = 0.2 mol . Mass = 0.2 × 62 = 12.4 g . 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.