<p> Leader: Lillian Howard Intro To Gibbs Free Energy Course: Chem 178 (B) Supplemental Instruction Instructor: Dr. Burnett Iowa State University Date: 4/10/13</p><p>1. If ΔH = -120.0 kJ and ΔS = -0.300 kJ/K, the reaction is spontaneous below a certain temperature. Calculate that temperature.</p><p>2. a. Calculate ΔH and ΔS for the following reaction. b. Is this reaction Endothermic or Exothermic c. Determine the ΔG˚ for this reaction at 25˚C d. Illustrate why NH4NO3 spontaneously dissolves is water at room temperature</p><p>+ - NH4NO3(s) + H2O(l)  NH4 (aq) + NO3 (aq)</p><p> o o Compound Hf (kJ/mol) S (J/mol-K)</p><p>NH4NO3 (s) -365.56 151.08 + NH4 (aq) -132.51 113.40 - NO3 (aq) -205.0 146.40</p><p>3. For the Oxidation of Iron to Rust 4Fe + 3O2  2Fe2O3</p><p>ΔH˚ rxn -1648.4 kJ/mol</p><p>ΔS˚ rxn -543.7 J/(mol K)</p><p>What is the standard Gibbs free energy (ΔG˚ rxn ) for this reaction?</p><p>1060 Hixson-Lied Student Success Center v 515-294-6624 v [email protected] v http://www.si.iastate.edu 4. For a certain chemical reaction ΔH˚ = -35.4 kJ and ΔS˚ = - 85.5 J/K. a. Is this reaction endothermic or exothermic? b. Does this reaction lead to an increase or decrease in randomness of the system? c. Calculate ΔG˚ for the reaction at 298 K. d. Is this reaction spontaneous at 298 K under standard conditions?</p><p>5. For each of the following pairs choose the substance with the higher entropy a. Ar (l) or Ar (g) b. He (g) at 3 atm or He (g) at 1.5 atm c. 1 mol of Ne (g) in 15 L or 1 mol Ne (g) in 1.5 L d. 1 mol P4 (g) at 300˚ C & 0.01 atm or 1 mol As4 (g) at 300˚ C & 0.01 atm</p><p>6. For the decomposition of barium carbonate, consider the following thermodynamic data:</p><p>Calculate the temperature in kelvin above which this reaction is spontaneous.</p><p>7. ΔH ˚ ΔS ˚ ΔG ˚</p><p>______Always spontaneous</p><p>______Always non-spontaneous</p><p>______Spontaneous over a certain temperature</p><p>______Non-spontaneous over a certain temperature</p>