1. HW 5.4 a. 200 KJ b. by 4 c. Heat up brakes and road. 5.18 a.  E = q + w b. No energy is not gained or lost. c. System loses heat or does work on the surroundings. 5.20 a. +478 kJ endothermic b. -3140 J exothermic c. -8.65 kJ exothermic 5.28 a. Constant p b. Independent of pathway c. Increase 5.30 a. ZnCO 3 (s)  ZnO(s) + CO 2 (g)  H = +71.5 kJ b. 5.34 a. absorbed b. 4.53 x 10 3 kJ c. 2.89 g d. -104 kJ

2. Calorimetry AP Chemistry

3. Calorimetry The measurement of heat flow. Heat flow depends on three things: 1. Mass of the object (m) 2. The temperature change (  T) 3. The material itself.

4. Specific heat capacity (s) The energy required to raise the temperature of 1 gram of a substance by 1 o C. Calorie: the energy required to raise the temperature of 1 gram of water by 1 o C. Which means the specific heat capacity of water is 1 cal/g o C, or 4.18 J/g o C.

5. Water has a very high specific heat capacity. This means it takes a lot of energy to raise the temperature of water. This is due to waters STRONG HYDROGEN BONDS!!!

6. Metals have very low specific heat capacity. S Fe = 0.449 J/g o C S Pb = 0.129 J/g o C This means metals heat up and cool down very quickly. It requires very little heat flow to change their temperature.

7. Heat flow (q) depends on three things: 1. Mass of the object (m) 2. The temperature change (  T) 3. The specific heat capacity of the material(C). These can be combined into an equation: q = m x C x  T

8. q = m C  T How much energy (heat) would be required to raise the temperature of 250.0 g of water from 25 o C to 100 o C?

9. q = mC  T What mass of lead would need 2340 J of heat to raise the temperature 25 o C?

10. Calorimeter Instrument used to measure heat flow. Usually consists of an insulated container and a heat sink (something to absorb the energy). Coffee cup calorimeter!!

11. Constant pressure calorimetry: For reactions that occur in solutions, water is the heat sink The reaction is the system. The heat gained by the solution is going to equal the heat lost by the reaction. q soln = - q rxn For dilute aqueous solutions the specific heat capacity of the solution is approximately the same as water, 4.18 J/gC

12. When a 9.55g sample of solid sodium hydroxide is dissolved in 100.0g of water in a coffee cup calorimeter, the temperature rises from 23.6 C to 47.4 C. Calculate H (in kJ/mol NaOH) for the solution process: NaOH(s)  Na + (aq) +OH - (aq) Assume the specific heat capacity of the solution is the same as pure water.

13. Bomb Calorimetry (Constant –volume calorimetry) Used to study combustion reactions. The substance is burned, and the temperature change of the water is measured. q rxn = -C cal x  T C cal is the heat capacity of the calorimeter, which is measured and calculated.

14. A 2.200 g sample of quinone (C 6 H 4 O 2 ) is burned in a bomb calorimeter whose total heat capacity is 7.854 kJ/ o C. The temperature of the calorimeter increases from 23.4 o C to 30.6 o C. What is the heat of combustion per gram of quinone?

15. Home work: Read sec: 5.5 to 5.6 EOC5: 5.44, 5.48, 5.50, 5.52