Welcome to Chem 1B CLAS with Eric Engel Webpage: clas.sa.ucsb.edu/staff/eric Email: eric.engel@sa.ucsb.edu Drop-In Hours: M 10-11, 4-5 Tu 3-5 W 10-11, 4-5 in SRB 3274 Th 4-5 F 12-1

Thermodynamics (Ch 9) 1. Fill in the following table: Positive (+) Negative (-) Zero (0) Heat (q) Work (w) ΔE

Thermodynamics (Ch 9) Constant Pressure Constant Volume q qp = nCp ΔT qp = ΔH qv = nCv ΔT qv = ΔE w w = -Pext ΔV or –nR ΔT or - ΔngRT w = 0 ΔE ΔE = q + w ΔE = nCv ΔT ΔH ΔH = ΔE + Δ(PV) ΔH = nCp ΔT

Thermodynamics (Ch 9) 2. Calculate the value of q, w, ΔE and ΔH for the following: a. 3 moles of a monatomic ideal gas is heated from 35 to 45 °C at a constant pressure of 3.6 atm. b. heating 500. g of nitrogen gas from 50.0 ˚C to 75.0 ˚C in a rigid container (for N2, Cv = 20.71 J/K mol and Cp = 29.03 J/K mol) c. cooling 500 g of nitrogen gas from 75.0 ˚C to 50.0 ˚C at a constant pressure of 1.00 atm d. The pressure of a 4.2 mole sample of N2 gas is decreased from 8.7 atm to 2.5 atm at a constant volume of 20.0 L.

Thermodynamics (Ch 9) 3. Consider 2.00 mol of a monatomic ideal gas that is taken from state A (2.0 atm, 10.0 L) to state B (1.00 atm, 30.0 L) by two different pathways: Path 1: A (2.0 atm, 10. L)  C (2.0 atm, 30. L)  B (1.0 atm, 30. L) Path 2: A (2.0 atm, 10. L)  D (1.0 atm, 10. L)  Calculate q, w, ΔE and ΔH for both pathways.

Thermodynamics (Ch 9) 4. Concept questions: a. For every gas, why is the value of Cp greater than Cv? By what constant are they related? b. Why is the value of Cp greater for nitrogen gas than neon?

Thermodynamics (Ch 9) 5. Predict the sign of q,w, Δ E and Δ H for the following that take place at 25 °C and 1 atm: a. 2 H (g)  H2 (g) b. N2(g) + 3H2(g)  2NH3(g) (only predict w) c. Fe2O3(s) + 3H2(g)  2Fe(s) + 3H2O(l) (only predict w) d. H2O(l)  H2O(s) e. Ammonium chloride is dissolved in water, and the solution’s temperature decreases.

Thermodynamics (Ch 9) 6. Calculate the heat released or absorbed for: a. 12 g of ammonia reacts with 25 g of oxygen according to the following reaction: 4NH3 + 5O2  4NO + 6H2O ΔH = -338 kJ b. Melting 36.0 g of ice at 0 °C and raising the temperature to 50.0 ° C. (ΔHfusion = 6.02 kJ/mol, CH2O liquid = 4.18 J/gC)

Thermodynamics (Ch 9) 7. If a 50.0 g sample of copper is heated to 85.0 ˚C and placed in 100 mL of water initially at 25.0 ˚C, what will be the final temperature of the water assuming no heat is lost to the surroundings? (Cwater = 4.18 J/g ˚C, Ccu = 0.20 J/g ˚C)

Thermodynamics (Ch 9) 8. Consider the dissolution reaction: CaCl2(s)  Ca2+(aq) + 2Cl-(aq) ΔH = -81.5 kJ If 20.0 g of calcium chloride are dissolved in 150. mL of water at 25.0 ˚C, what will be the final temperature of the solution assuming no heat loss to surroundings? (assume heat capacity of solution is 4.18 J/g C)

Thermodynamics (Ch 9) 9. Given the following: P4(s) + 6Cl2(g)  4PCl3(g) ΔH = -1226 kJ P4(s) + 5O2(g)  P4O10(s) ΔH = -2967 kJ PCl3(g) + Cl2(g)  PCl5(g) ΔH = -84 kJ PCl3(g) + ½ O2(g)  Cl3PO(g) ΔH = -286 kJ Calculate ΔH for the reaction: P4O10(s) + 6 PCl5(g)  10 Cl3PO(g)

Thermodynamics (Ch 9) 10. Write the reaction that corresponds to the enthalpy of formation of the following compounds: a. CH4 (g) b. NaCl (s) c. CH3OH (l)

Thermodynamics (Ch 9) 11. How much heat is released when 1 mole of methane (CH4) is burned? Use the following data: ΔHf˚ CH4 (g) -75 kJ/mol CO2 (g) -394 kJ/mol H2O(g) -242 kJ/mol

Thermodynamics (Ch 9) Bonus Q: If the heat of vaporization of water is 41 kJ/mol, what is the heat of formation of liquid water? (hint: use data from the last problem)

Thermodynamics (Ch 9)