Practice question

Given: Calculate the heat absorbed by 18 g of water to vaporize at 373 K, given Δ_{vap H° = 40.79 kJ/mol (molar mass of water = 18 g/mol). These values define the system as per NCERT data. Formula: Moles = 18 / 18 = 1 mol. This is the standard NCERT relation for this phenomenon. Substitution & Calculation: Heat absorbed = n × Δ_{vap H° = 1 × 40.79 = 40.79 kJ. 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.