A 74.6 g ice cube floats in the Artie Sea. The pressure and Temperatures of the

Question

A 74.6 g ice cube floats in the Artie Sea. The pressure and Temperatures of the system and surroundings are at 1 atm and 0 degree C, receptively. Calculate Delta S_sys, Delta S_surr, Delta S_total for the melting of ice cube under these conditions. What can you conclude about the nature of the process from the value of Delta S_total? (The molar heat of fusion of water is 6.01 kJ/mol.) b) The sublimation point for dry ice is -78.5 degree C at 1 atm. Sublimation reaction, CO_2(s) rightarrow CO_2(g) has Delta H degree_sublimation = 25.2 kJ/mol. Determine Delta S degree_sublimation

Explanation / Answer

18.

a) dSsurr = dHsur/Tmelt

               = -74.6 x 6.01/18 x 273

               = -24.91 kJ/273 K

               = -91.2 J/K.mol

dSsys = 69.9 - 41 = 28.9 J/K.mol

dStot = -91.2 + 28.9 = -62.3 J/K.mol

The process is exothermic in terms of overall entropy change.

b) For the given reaction and data,

Tsubl = -78.5 + 273 = 194.5 K

dHosubl = 25.2 kJ/mol

So,

dSosubl = dHosubl/Tsubl = 25200/194.5 = 129.563 J/K.mol

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