Answer to Question #330764 in Physical Chemistry for Alli

Question

Suppose we have 2.0 g of ethyl alcohol at -50 degree celsius and we remove heat to it continuously. let us also assume that no heat is lost to the surroundings. How much heat is to be removed to convert this from liquid to solid at -120 degree celsius.

Answer 1

Moles = 2.0 / 46 = 0.043 mol

From -50 to -114C (freezing point): 118 J/mol*K x 0.043 mol x (114 – 50) = 328 J

At -114C: 4.9 kJ/mol * 0.043 mol = 210.7 J  

From -114 to -120: 118 J/mol*K x 0.043 mol x (120 – 114) = 30.4 J

Together: 328 + 210.7 + 30.4 = 569.1 J