Question

From data below, calculate the total heat (in J) associated with the conversion of 0.442 mol ethanol gas (C2H6O) at 501°C and 1 atm to liquid ethanol at 25.0°C and 1 atm. (Pay attention to the sign of the heat.)

Boiling point at 1 atm 78.5°C

cgas 1.43 J/g°C

cliquid 2.45 J/g°C

H°vap 40.5 kJ/mol

Answer 1

ass of ethanol = no of moles * molar mass
                 = 0.442*46
                 = 20.332gm
gas cool to 78.5C
q = mcdT
   = 20.332*1.43(501-78.5)
   = 12284.086 joules
gas condense into liquid
q = Cn
   = 40,500*0.442
   = 17901 joules
cool liquid 78.5to 25C
q = mcdT
   = 20.332*2.45*(78.5-25)
   = 20.332*2.45*53.5
   = 2665.01 joules
total heat = 12284.086+17901+2665.01
           = 32850 joules
           = 32.850kj