Question

Calculate the enthalpy change associated with the following process:

a) m-cresol is heated from 25°C to 100°C

b) Ethylene glycol is cooled from 15° to 120°C

c) Succinic acid is heated from 15°C to 65°C

d) Air is cooled from 15°C to 65°C

Answer 1

Enthalpy change expression will be: Ah=C,AT Ah=C,(Iz-I) As the mass or moles of the compounds are not given in the question so I have calculated the specific enthalpy of the compounds. (a) m-cresol heated from 25°C to 100°C. m-cresol is an organic liquid. The heat capacity of the m-cresol with in the temperature range of 21°C to 197°C is given as: C, = 0.551 from a standard text book. from a 8. c Then, the enthalpy change will be: Ah=C,AT Ah=C,(T2-T) =0.551 colex(100°C – 25°C) =0.551_cal (100-25) Ah=41.325 cal

(b) Ethylene glycol is cooled from 15°C to 120°C. The heat capacity of Ethylene glycol in between the given temperature range is C, = 0.525.cc Then, Ah =C,(1, -1) *(120°C-15°C) =0.525_cal 8. °C (120°c = 0.525_cal*(120–15) C Ah = 55.125 cal

(c) Succinic acid is heated from 15°C to 65°C. The heat capacity of Succinic acid is, C, =(0.248+0.00153T), and this value of heat gic and this capacity is in between the temperature range of 0°C to 160°C. So, I have taken the man temperature of the given value of 15°C to 65°C and use that value for T. Ten, the heat capacity value will be: C, =(0.248 +0.001537) cal g. °C =(0.248+0.00153(15465), con =0.309_cal 8°C Then, Ah=CdT (0,248+0.00153T)dT = |(0.248+0.001537 )d1 (0248+0.00153T) dT = 0.248 (65–15)+0.00153 (65)_(1520 Ah=15.46 cal

(d) Air is cooled from 15°C to 65°C. Ah=C,d1 =(a+bT+cT? +dT?) dT = f(a+b7 +cT2 +dT°)dt 28.94 +0.4147x10-2T +0.3191x10-12-1.965x10-1]dT 28.94 (65–15) +0.4147102( (65) (153* +0.3191*10*(65*_(.5")-1 1965-10-f(" as a sh=1455.57 met