Thermodynamics (Ch 10) 1. One mole of helium in a volume of 1.0 L at 5.0 atm pressure is allowed to expand isothermally into a volume of 2.0 L. Calculate the work done if: a. the gas expands into an evacuated container b. the gas expands, in one step, against a constant external pressure of 2.5 atm c. the gas expands reversibly

Thermodynamics (Ch 10) 2. For the following, state whether there will be an increase or decrease in entropy. a. freezing water b. dissolving calcium chloride c. formation of NH 3 (g)

Thermodynamics (Ch 10) 3. Circle the one with the greatest entropy. a. 1 mol of He at STP or 1 mol of He at 50 ˚C and 1 atm b. 1 mol of N 2 at STP or 1 mol of SF 6 at STP c. 1 mol of Ne at 25 ˚C, 1 atm or 1 mol of Ne at 25 ˚C, 0.01 atm

Thermodynamics (Ch 10) 4. A sample of ice weighing 36.0 g, initially at ˚C, is heated to 150. ˚C at a constant pressure of 1.00 atm. Calculate q, w, ΔE, ΔH and ΔS for this process. (C p (ice) = 37.5 J/Kmol, C p (liquid) = 75.3 J/Kmol C p (gas) = 36.4 J/K mol, ΔH fusion = 6.01 kJ/mol, ΔH vaporization = 40.7 kJ/mol)

Thermodynamics (Ch 10) 5. Calculate the change in entropy that occurs when 3.00 mol of liquid water at 0.0 ˚C is mixed with 1.00 mol of water at 90. ˚C in a perfectly insulated container. (C p = 75.3 J/K mol)

Thermodynamics (Ch 10) 6. Consider the freezing of water. a. Use the following to calculate ΔH˚ and ΔS˚ for this process. ΔH˚ f S˚ H 2 O (l) -286 kJ/mol 70 J/K mol H 2 O (s) -292 kJ/mol 48 J/K mol b. Calculate a value for ΔG˚ for this process at three different temperatures: 25 ˚C, -15 ˚C and 0 ˚C.

Thermodynamics (Ch 10) ΔH ΔS Spontaneous? - + Always - - At low T only + + At high T only + - Never

Thermodynamics (Ch 10) 7. The melting point of tungsten is 3680 K. The enthalpy of fusion is 35.2 kJ/mol. What is the entropy of fusion for tungsten ?

Thermodynamics (Ch 10) 8. Consider the reaction 2 POCl 3 (g)  2 PCl 3 (g) + O 2 (g) a. Calculate ΔG˚ for this reaction, given that the ΔG˚ f values for POCl 3 (g) and PCl 3 (g) are -502 kJ/mol and -270 kJ/mol, respectively. b. Is the reaction spontaneous under standard conditions at 298 K? c. The value of ΔS˚ for the reaction is 179 J/K mol. At what temperatures is this reaction spontaneous?

Thermodynamics (Ch 10) 9. Given the following reaction at 800 K: N 2 (g) + 3 F 2 (g)  2 NF 3 (g) a. An equilibrium mixture contains the following partial pressures: atm N 2, atm F 2 and 0.48 atm NF 3. Calculate ΔG˚ for the reaction at 800 K. b. What is ΔG if the pressures of the gases are 0.1 atm F 2, 0.1 atm N 2 and 5 atm NF 3 at 800 K.

Thermodynamics (Ch 10) 10. The equilibrium constant for a certain reaction decreases from 8.84 to when the temperature increases from 25 to 75 ˚C. Is the reaction endo- or exothermic? Calculate ΔH˚ for the reaction.