The molar heats of fusion and vaporization of ethanol are 7.61 and 26.0 kj/mol, respectively. calculate the molar entropy changes for the solid-liquid and liquid-vapor transitions for ethanol. at 1 atm pressure, ethanol melts at −117.3â°c and boils at 78.3â°c.

ΔS= 0.0194 KJ/K.mol

ΔS= 0.074 KJ/K.mol

Explanation:

 Heat of fusion

   Heat required to convert solid state of substance in to liquid state is know as heat of fusion.The temperature remains same during conversion of states .

 Heat of vaporization:

 The heat required to  convert liquid state of substance in to vapor state is know as heat of vaporization.The pressure remains same during conversion of states .

We know that

Entropy change

ΔS= Q /T

Molar entropy changes for the solid-liquid:

 ΔS= Q /T

ΔS= 7.61 /(273+117.3) KJ/K.mol

ΔS= 0.0194 KJ/K.mol

Molar entropy changes for the liquid-vapor:

ΔS= 26/(273+78.3) KJ/K.mol

ΔS= 0.074 KJ/K.mol

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