Question

From data below, calculate the total heat (in J) associated with the conversion of 0.655 mol ethanol gas (C2H6O) at 351°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

mass of ethanol = no of moles of ethanol* molar mass of ethanol

                       = 0.655* 46 = 30.13 gm

Q = mCT

     = 30.13*1.43*(351-25)

    = 30.13*1.43*326 = 14046 joules

condense to gas to liquid

q = cn

= 40500*0.655 = 26527.5 joules

cool liquid 78.5C⁰ to 25C⁰

Q = mCT

    = 30.13*2.45*(78.5-25)

= 3949.28 joule

toal heat = 14046+ 26527.5 +3949.28 =44522 . 78joules

required energy is + sign