Question

Exercise #6: Enthalpy Problems Calorimetry Problems: AH = m(at)c, 500 kg of water cools from 95°C to 20°C. How much heat energy was released by the water? C, of H2O(l) is 4.180 J/gºC. 2. How much heat energy is required to heat 45 g of sheet Fe from 24°C to 200°C? C of Fe(s) is 0.449 J/gºC. 3. A food chemist combusts 56 g of a chocolate bar in a calorimeter containing 1.5 L of water (density H,0 = 1g/ImL). The initial temperature was 19°C and the final temperature was 73°C. How much heat energy was absorbed by the water? What was the AH., for this combustion reaction? 4. 5.00g of uranium is cooled from 55°C to 18°C. The heat released was 20.35J (AH = -20.35J). Calculate the specific heat capacity (c) for uranium. 5. Predict the final temperature of 1.5 L of water within a calorimeter when 10.0 g of potato chips are combusted. The initial temperature of the water was 19°C and the heat energy absorbed by the water (released by the potato chips) was 62.8kJ (AH = 62.8kJ).

Answer 1

. . . . . . . . " Heat energy realsed or absorbed = m Sot ma man y Substance Co= specific heat capacity OT: diference in Tempranire . lkg = 1000g 5ooks = 500,ooog Ta= final Temp. - AT = Tz-Ti Ti = Tinat Temp. - DT= 20°c - 95c =-15 Initial heat realsed = - 500,ooog x 4.180 I x 754 - . - -15675 0000 J DHE -156750 kJ Answer ( 13=0.004KJ) - 2 Difference in temp = Tg-T, = 200°C-QuC= 1763 q= 457 x 0.449 IX1769 = 3556.08 heat required=+3556:08 = 3.56 kJ I . Answer