1. Monday 13 October 2014 Read: –Section 3.3. Problems: –3.16, 3.18, 3.22, 3.36.

2. 3 4 1 2 5 6

3. Sample Problem 2.00 mole of Nitrogen at 1.00 atm, 25°C is allowed to Expand isothermally to final pressure of 0.132 atm. Calculate work done if the expansion is carried out a.) against a vacuum b.) against a constant external pressure of 0.132 atm c.) reversibly

4. Solution: a.) against a vacuum P ex = 0 (no weight) w = -P ex ΔV = 0 No work! 4

5. Solution: b.) against a constant external pressure of 0.132 atm Work will be done in expansion on surroundings 5

6. Solution: c.) reversible expansion Work will be done in expansion on surroundings 6

7. Total Energy And Internal Energy 2 2 1 1 Translational Energy Rotational Energy Vibrational Energy Electronic Energy Chemical Energy h Total Energy Internal Energy ? ? PE = m g h KE = ? h KE = ½ mv 2 > 0 PE = m g h

8. HEAT is NOT Energy BUT Transfer of Energy 3 3 Energy of isolated system is conserved E1E1 E1E1 E2E2 E2E2 E = E 1 + E 2 = C ΔE = C – C = 0 E = E 1 + E 2 = C ΔE = C – C = 0 -q 1 +q 2 E = E 1 + (-q 1 ) + E 2 + (+q 2 ) = C ∑q i = 0 E 1 E 2 ? ? E = E 1 + E 2 + (-q 1 ) + (+q 2 ) = C (-q 1 ) + (+q 2 ) = ? ? ? 25 o C 70 o C 25 o C 100 o C 25 o C 70 o C

9. Exothermic Endothermic HEAT is NOT a State Function 3 3 100 K 200 K ΔE in 0 ? ? 200 K 100 K ΔE in 0 ? ? Initial State Final State q > 0 q = 0

10. How do we measure HEAT transfer (q)? Using constant-volume adiabatic bomb Calorimeter 4 4

11. Sample Problem 100.0 g of nickel at 150.° C was placed in 1.00 L of water at 25.0° C. What is the final temperature of the water after thermo- equilibrium has been established. Assume this is an isolated system and heat is only transferred between nickel and water (not to surroundings). The specific heat capacity of nickel is 0.440 J·g - 1 ·C -1.

12. Solution: 1 cal = 4.184 J exactly 1 cal = energy needed to raise 1 g of water by 1° from 14.5° to 15.5°C Heat lost by nickel = heat gained by water -q Ni = q water 12

13. First law of thermodynamics 5 5 Under Constant Pressure ex. Lab bench Under Constant Pressure ex. Lab bench Under Constant Volume ex. Bomb Calorimeter Under Constant Volume ex. Bomb Calorimeter Irreversible gas expansion

14. Enthalpy, a new State Function 5 5 Under Constant Pressure ex. Lab bench Under Constant Pressure ex. Lab bench Under Constant Volume ex. Bomb Calorimeter Under Constant Volume ex. Bomb Calorimeter qpqp qpqp -w qvqv qvqv ΔU ΔH ? ? If gas expands qvqv qvqv -w qpqp qpqp If gas compresses

15. Sample Problem 0.5122g of Naphthalene (C 10 H 8, MW=128.2 g/mol) was “combusted” in a constant-volume calorimeter (C V = 5267.8 J·K -1 ), where the water temperature increased from 20.17° to 24.08°C. Calculate the molar ΔH and ΔU (@ 20.17°C) for the combustion (oxidation) of Naphthalene (units: kJ·mole -1 ).