Question

16. (10 pts) The entropy change for the change of state C,H-OH (1) ------- CHOH (2) is 20 J/mol.K, the enthalpy of vaporization of the liquid is 3.20 kJ/mol. a. What is the boiling point of the substance? b. What will be the entropy change for the condensation of 4.60 grams of C,H,OH vapor? (molar mass of CHOH is 46.0 g mol) (R=0.08205 L atm mol.K, R= 8.314 J mol.K, F = 96481 C mol electron)

Answer 1

no bruiven for the vaporisation . of ethanol , C₂H5014 C Hg OH (2) C₂H50 H (G) Change of entropy = 20 5/mol R ie. As vap = 20 5 | melk - And Change of enthatoy, - il D Hvap: 3:20 kJ/mol Note that for any substantee at its boiling point or freezing point; A = 0 where Aly= Change in bibb's free energies.

Using formula Alys AH - TAS 0 E DH - TAS π = A Huap of = . Asvap . .= 3.20 kJ /mol 20 J1 mol K = 3.20 x 1000 J/mol 20 J/mol K T = 160k boiling point of ethanol is 160k. Thus, the the liquid bo in of We need to calculate change entropy for the condensation 4.60 grams of C₂H5 OH -

Boiling C H50 HG) C₂ H GOH (2) 'Condensation Condensation is the reverse of boiling. for the reverse reaction, sign. of as changes. buven us for boiling = 20 J | melk → As for condensation = -20 J/mol K Criven Mass of C H5OH = 4060 gm Molas Mass of G H 50th is 46•0 g/mol As No. of Moles = briven Mass i Molar Mass

= Moles of C H g OH = 4.60 46-O - = 0 • 10 mol As A S = -20 51 mol K for 1 mol of C2 150H & As for Oo 10 mol C₂ H GOH -20 Il mol K x 0.10 mol -200 J/K : . Thus AS = -2 J/K. I Hence, the entropy change for the condensation of 4.60 gm of C₂H5OH is az 5 lk.