University:
Bradley University
Course:
CHM 116 | General Chemistry II
Academic year:

2023
Views:

118

Pages:

3
Author:

Herbosambx

PAL – Week 8 (Wed/Th) #13 Thermo Part 2 (sec 17.5-17.7) Name Part A: Using the Change in Gibbs Free Energy to predict spontaneity Fill in the Blanks: Fill in the blanks with ( <, >, =) If ΔG ___ 0; the reaction is at equilibrium If ΔG ___0; the reaction will proceed spontaneously towards products If ΔG ___0; the reaction will proceed spontaneously towards reactants (is nonspontaneous in the forward direction). True and False: True or false? All exothermic reactions are spontaneous? ______ Nature tends towards lower energy and more disorder. ________ Part B: Calculating the Change in Gibbs Free Energy under Non-standard Conditions 1. The reaction below is endothermic and spontaneous at T = 525 K. Please answer the following questions and discuss your answers with your PAL group. 2 HNO3(aq) + NO(g) → 3 NO2(g) + H2O(l) a) Which of the following must be true? Circle your answer. ΔG > 0; ΔS > 0; ΔH > 0 ΔG < 0; ΔS > 0; ΔH > 0 ΔG > 0; ΔS < 0; ΔH > 0 b) Calculate ΔG for the reaction above using the following information ΔH = +136.5 kJ; ΔS = +287.5 J/K at a Temp = 525 K. c) Why do you think reaction is spontaneous? Take a look at the reaction. What do you notice? d) At what temperature will the reaction be non-spontaneous? 1 Part B: Calculating the Change in Gibbs Free Energy under standard conditions 2. Calculate the ΔG°rxn using the following information. 4 HNO3(g) ΔG°f (kJ/mol) -73.5 + 5 N2H4(l) → 7 N2(g) + 12 H2O(l) 149.3 ΔG°rxn = ? -237.1 3. Calculate the ΔG°rxn using the following information. ΔH°f (kJ/mol) S°(J/mol·K) 4 HNO3(g) + 5 N2H4(l) → 7 N2(g) + 12 H2O(l) ΔG°rxn = ? -133.9 50.6 -285.8 266.9 121.2 191.6 70.0 What do you notice about your answer to 2 and 3? Do they agree? o 4. Calculate ΔG by adding Gibbs Free Energies of Reactions (ΔG o 1 + ΔG o 2 o + ΔG 3…) Use Hess's law to calculate ΔG°rxn using the following information. ClO(g) + O3(g) → Cl(g) + 2 O2(g) ΔG°rxn = ? 2 O3(g)→ 3 O2(g) Cl(g) + O3(g) → ClO(g) + O2(g) ΔG°rxn = +489.6 kJ ΔG°rxn = -34.5 kJ 2 o 5. Calculate ΔG by adding Gibbs Free Energies of Reactions (ΔG NO(g) + O(g) → NO2(g) 2 O3(g) → 3 O2(g) O2(g) → 2 O(g) NO(g) + O3(g) → NO2(g) + O2(g) o 1 + ΔG o 2 o + ΔG 3…) ΔG°rxn = ? ΔG°rxn = +489.6 kJ ΔG°rxn = +463.4 kJ ΔG°rxn = - 199.5 kJ A) +753.5 kJ B) +277.0 kJ C) -676.0 kJ D) -1152.5 kJ E) -225.7 kJ 3