Equilíbrio Químico: Reações e Pressões

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308 Chapter 15 Chemical Equilibrium Solution: P₁V₁ = P₂V₂ (0.0260 (10.0L) = x = 2.60 atm MgCO₃(s) MgO₃(s) + CO₂(g) Initial 2.60 Change -x Equil 2.60 Kₚ = = 0.026 = 2.60 x x = 2.579 atm 1 mol = = 0.4835 mol CO₂ 1.0 X = 0.0248 mol MgO mol K gMgO Therefore, MgO is the limiting reactant and produces 0.0248 mol MgCO₃. 0.0248 1 = 2.09 Check: The units (g) are correct. The magnitude (2) is reasonable since the pressure and volume are small. Much less than 1 mole is anticipated. 15.79 Given: C₂H₄(₈) + is exothermic Find: Which of the following will maximize C₂H₄Cl₂? (a) Increasing the reaction volume will not maximize C₂H₄Cl₂. The chemical equation has 1 mole of gas on the right and 2 moles of gas on the left. Increasing the volume of the reaction mixture decreases the pressure and causes the reaction to shift to the left (toward the side with more moles of gas particles). (b) Removing C₂H₄Cl₂ as it forms will maximize C₂H₄Cl₂. Removing the C₂H₄Cl₂ will decrease the concentration of C₂H₄Cl₂ and will cause the reaction to shift to the right, producing more C₂H₄Cl₂. (c) Lowering the reaction temperature will maximize C₂H₄Cl₂. The reaction is exothermic, so we can think of heat as a product. Lowering the temperature will cause the reaction to shift to the right, producing more C₂H₄Cl₂. (d) Adding Cl₂ will maximize C₂H₄Cl₂. Adding Cl₂ increases the concentration of Cl₂, so the reaction shifts to the right, which will produce more C₂H₄Cl₂. 15.81 Given: reaction 1 at equilibrium: PH₂ = 0.958 atm, = 0.877 atm, PHI = 0.020 atm; reaction 2: PH₂ = = 0.621 atm, PHI = 0.101 atm Find: Is reaction 2 at equilibrium? If not, what is the PHI at equilibrium? Conceptual Plan: Use equilibrium partial pressures to determine Use to determine whether reaction 2 is at equilibrium. Prepare an ICE table, calculate Q, compare Q and Kₚ, predict the direction of the reaction, represent the change with x, sum the table, determine the equilibrium values, put the equilibrium values in the equilibrium expression, and solve for x. Determine Solution: + 2HI(g) Reaction 1: PH₂ PHI Equil 0.958 0.877 0.020 Kₚ = = (0.958)(0.877) = 4.7610 X 10⁻⁴ Q = = 0.0264 Q > K, so the reaction shifts to the left. (0.621)(0.621) + 2HI(g) Reaction 2: PH₂ PHI Initial 0.621 0.621 0.101 Change +x +x Equil 0.621 + 0.101 2x = = (0.621 (0.101 + + = 4.7610 X 10⁻⁴ Copyright © 2017 Pearson Education, Inc.