What quantity of energy does it take to convert 0.500 kg ice at 20.c to steam at 250.c? specific heat capacities: ice, 2.03 j/g c; liquid, 4.2 j/g c; steam, 2.0 j/g c; hvap 40.7 kj/mol; hfus 6.02 kj/mol. 98?
1680kJ Heat 500 g ice from -20 to 0 deg C: 500 g x 2.03 j/g C x 20 deg = 20300 J = 20.3 kJ (20 kJ) Convert 500 g ice at 0 deg to 500 g water at 0 deg: 500 g / 18.015 g/mol = 27.75 mol 27.75 mol x 6.02 kJ/mol = 167.0 kJ (167 kJ) Heat 500 g water from 0 deg to 100 deg C: 500 g x 4.2 J/g C x 100 deg = 210000 J = 210 kJ (210 kJ)
Convert 500 g water at 100 deg to 500 g steam at 100 deg C: 27.75 mol x 40.7 kJ/mol = 1129.4 kJ (1130 kJ) Heat 500 g steam from 100 deg to 250 deg C: 500 g x 2.0 J/g C x 150 deg = 50000 J = 50 kJ (50 kJ) Add all the steps: 20 + 167 + 210 + 1130 + 50 = 1577 kJ (1580 kJ to 3 sig. figures) Are you certain the book says 1680 and not 1580 kJ? EDIT: Math error in heating steam; should be 150 kJ not 50 kJ ANSWER: 20 + 167 + 210 + 1130 +150 = 1677 kJ Using 3 significant figures, the answer is 1680 kJ
