Chemical Equilibrium (ppt) - Berkeley City College：化学平衡（PPT）-伯克利城市学院.pptVIP

Why is Equilibrium Constant Important? Knowing Kc and the initial concentrations, we can determine the concentrations of components at equilibrium. Equilibrium Exercise #5 For the reaction: CO(g) + 2 H2(g) ? CH3OH(g), Kc = 14.5 at 500 K. Predict whether a mixture that contains 1.50 mol of H2, 1.00 mol of CO, and 0.50 mol of CH3OH in a 10.0-L vessel at 500 Kc is at equilibrium. If not, indicate the direction in which the net reaction will occur to reach equilibrium. (Answer: Qc = 22.2 Kc; net reaction is to the left) Calculating equilibrium concentrations using initial concentrations and value of Kc Consider the reaction: H2(g) + I2(g) ? 2 HI(g), where Kc = 55.6 at 425oC. If [H2]0 = [I2]0 = 0.1000 M, and [HI]0 = 0.0 M, what are their concentrations at equilibrium? Using the ICE table to calculate equilibrium concentrations Equation: H2(g) + I2(g) ? 2 HI(g), ??????????????????????????????????????????????? Initial [ ], M 0.1000 0.1000 0.0000 Change [ ], M -x -x +2x Equilibrium [ ], M (0.1000 - x) (0.1000 - x) 2x ???????????????????????????????????????? ??????? Calculation of equilibrium concentrations Equilibrium Exercise #6 For the reaction: 2 NO2(g) ? N2O4(g); Kp = 1.27 at 353 K. If the initial pressure of NO2 was 3.92 atm, and initially there was no N2O4, what are the partial pressures of the gases at equilibrium at 353 K? What is the total gas pressure at equilibrium? (Answer: PNO2 = 1.06 atm; PN2O4 = 1.43 atm; Ptotal = 2.49 atm) Equilibrium Exercise #7 The reaction: PCl5(g) ? PCl3(g) + Cl2(g) has Kc = 0.0900. A 0.1000-mol sample of PCl5 is placed in an empty 1.00-L flask and the above reaction is allowed to come to equilibrium at a certain temperature. How many moles of PCl5, PCl3, and Cl2, respectively, are present at equilibrium? (Answer: PCl5 = 0.0400 mol; PCl3 = Cl2 = 0.0600 mol) Le Chatelier’s Principle The Le Chateliers principle states th