Calculate the change of entropy (in J K^-1 mol^-1) when 1 mol of ethanol is cooled at constant pressure from 25 °C to 10 °C, the molar heat capacity, C_p, of ethanol is 111.5 J K^-1 mol^-1 and assume that C_p is constant over this temperature range.

Question

Quizplus · Accepted Answer

The change in entropy can be calculated using the formula ΔS = nCln(T2/T1), where n is the number of moles of the substance, C is the molar heat capacity, T1 is the initial temperature, and T2 is the final temperature. 
Substituting the given values, ΔS = (1 mol)(111.5 J K-1 mol-1) ln(283.15 K/ 298.15 K) = -5.8 J K-1 mol-1. The negative sign indicates a decrease in entropy, as the ethanol is cooled at constant pressure.

Calculate the Change of Entropy (In J K-1 Mol-1) When

Calculate the Change of Entropy (In J K^-1 Mol^-1) When