Pure ZnO is reduced by the stoichiometric amount of carbon in a retort at 25°C
(298K). The products leave the retort at 907°C (1180 K).
ZnO(s, 25°C) + C(graphite, 25°C) = Zn(g, 907°C, 1 atm) + CO(g, 907°C, 1 atm)
Calculate the amount of heat per kg of zinc produced, which must be transmitted to
the retort for complete reaction.
Given:
i.
ii.
iii.
iv.
Standard heats of formation of ZnO and CO at 25°C (298 K) are -83.2
kcal/mole (-348.11 kJ/mol) and -26.42 kcal/mole (-110.54 kJ/mol)
respectively.
Heat of fusion of zinc at M.P. (420°C) = 1.74 kcal/mole (7.28 kJ/mol)
Heat of evaporation of zinc at B.P. (907°C) = 27.3 kcal/mole (114.22
kJ/mol)
Molar heat capacity of zinc at constant pressure = 5.35 + 2.40 x 10-3 T
cal/deg/mole (22.38 + 10.04 x 10-3TJ/K/mole) in the temperature range 25° 420°C (298-693 K) ,and =7.75 cal/deg/mole (32.43 J/K/mol) in the
temperature range 420° - 927°C (693 - 1200 K)
Molar heat capacity of CO at constant pressure = 6.8 + 0.98 x 10-3 T - 0.11 x 105T-2
cal/deg/mole (28.45 + 4.10 x 10 -3 T - 0.46 x 105 T-2 J/K/mol) in the temperature
range 25°-