25. The heat capacity of acetone vapor is temperature dependent and is given by

Question

25. The heat capacity of acetone vapor is temperature dependent and is given by CRm = a-(b/T) where, a= 182 J/mol-K and ba 36 kj/mol. Calculate the entropy change of the system and surroundings when two moles of acetone is heated from 100°C to 400°C 26. Consider three moles of argon gas is confined in a 10 L container at 25°C. Calculate the entropy change (ASs) if the gas is simultaneously heated to 200°C and compressed to 2L volume. 27. Calculate ASsrs, asSUR and .Mv when 2 moles of liquid water freezes at-100C.. The following data is given: CPnkpd =75.3 J/mol-K CPmold 37.7 J/mol-K ,H (273K)= +60101/mol-K AH(263K)-5634 J/mol-K 28. Calculate ASsys, ASSUR and ASUNrv when one mole of liquid Benzene vaporizes at 100 C. The normal boiling point of benzenes 800. The following data is given: CPa-= 138.7 J/mol-K Cm -35.1 J/mol-K 44H (353K)= +35.7 kJ/mol-K 44H (373K)= +33.63 kJ/mol-K

Explanation / Answer

Ans 25

Change in entropy dS = dQ/T

dS = nCp dT/T

= n (a-b/T) dT/T

dS = nadT/T - nbdT/T 2

By taking integration

S2-S1 = na ln (T2/T1) + nb(1/T2 - 1/T1)

= 2 mol x 182 J/mol-K x ln (673/373) + 2 mol x 36000 J/mol x (1/673 - 1/373) 1/K

= 214.82 J/K - 86.05 J/K

= 128.77 J/K

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