A 0.42-kg quantity of ethanol,in the liquid state at its melting point of -114.4°C,is frozen at atmospheric pressure.The heat of fusion of ethanol is 1.04 × 10⁵ J/kg,and its molecular mass is 46.1 g/mol.What is the change in the entropy of the ethanol as it freezes?

Question

Quizplus · Accepted Answer

The change in entropy (ΔS) when a substance freezes is given by ΔS = -Q/T, where Q is the heat removed and T is the temperature in Kelvin. The heat removed Q = mass × heat of fusion = 0.42 kg × 1.04 × 10^5 J/kg = 43680 J. The temperature in Kelvin is -114.4°C + 273.15 = 158.75 K. Thus, ΔS = -43680 J / 158.75 K ≈ -275 J/K, which is closest to -280 J/K.

A 042-Kg Quantity of Ethanol,in the Liquid State at Its Melting