Chapter 17 Chemical Equilibrium

The Equilibrium Constant Example 17-1: Write equilibrium constant expressions for the following reactions at 500oC. All reactants and products are gases at 500oC.

The Equilibrium Constant

The Equilibrium Constant

The Equilibrium Constant Example 17-2: One liter of equilibrium mixture from the following system at a high temperature was found to contain 0.172 mole of phosphorus trichloride, 0.086 mole of chlorine, and 0.028 mole of phosphorus pentachloride. Calculate Kc for the reaction. Equil []’s 0.028 M 0.172 M 0.086 M You do it!

The Equilibrium Constant

The Equilibrium Constant Example 17-3: The decomposition of PCl5 was studied at another temperature. One mole of PCl5 was introduced into an evacuated 1.00 liter container. The system was allowed to reach equilibrium at the new temperature. At equilibrium 0.60 mole of PCl3 was present in the container. Calculate the equilibrium constant at this temperature.

The Equilibrium Constant

The Equilibrium Constant Example 17-4: At a given temperature 0.80 mole of N2 and 0.90 mole of H2 were placed in an evacuated 1.00-liter container. At equilibrium 0.20 mole of NH3 was present. Calculate Kc for the reaction.

The Reaction Quotient Example 17-6: The equilibrium constant for the following reaction is 49 at 450oC. If 0.22 mole of I2, 0.22 mole of H2, and 0.66 mole of HI were put into an evacuated 1.00-liter container, would the system be at equilibrium? If not, what must occur to establish equilibrium?

Uses of the Equilibrium Constant, Kc Example 17-7: The equilibrium constant, Kc, is 3.00 for the following reaction at a given temperature. If 1.00 mole of SO2 and 1.00 mole of NO2 are put into an evacuated 2.00 L container and allowed to reach equilibrium, what will be the concentration of each compound at equilibrium?

Uses of the Equilibrium Constant, Kc

Uses of the Equilibrium Constant, Kc Example 17-8: The equilibrium constant is 49 for the following reaction at 450oC. If 1.00 mole of HI is put into an evacuated 1.00-liter container and allowed to reach equilibrium, what will be the equilibrium concentration of each substance?

Uses of the Equilibrium Constant, Kc

Disturbing a System at Equlibrium: Predictions Example 17-9: Given the reaction below at equilibrium in a closed container at 500oC. How would the equilibrium be influenced by the following?

Disturbing a System at Equlibrium: Predictions Example 17-10: How will an increase in pressure (caused by decreasing the volume) affect the equilibrium in each of the following reactions?

Disturbing a System at Equlibrium: Predictions Example 17-11: How will an increase in temperature affect each of the following reactions?

Disturbing a System at Equilibrium: Calculations Example 17-13: Refer to example 17-12. If the initial volume of the reaction vessel were halved, while the temperature remains constant, what will the new equilibrium concentrations be? Recall that the original concentrations were: [A]=0.20 M, [B]=0.30 M, and [C]=0.30 M. You do it!

Disturbing a System at Equilibrium: Calculations

Disturbing a System at Equilibrium: Calculations

Disturbing a System at Equilibrium: Calculations

Disturbing a System at Equilibrium: Calculations Example 17-14: A 2.00 liter vessel in which the following system is in equilibrium contains 1.20 moles of COCl2, 0.60 moles of CO and 0.20 mole of Cl2. Calculate the equilibrium constant.

Disturbing a System at Equilibrium: Calculations An additional 0.80 mole of Cl2 is added to the vessel at the same temperature. Calculate the molar concentrations of CO, Cl2, and COCl2 when the new equilibrium is established. You do it!

Disturbing a System at Equilibrium: Calculations

Disturbing a System at Equilibrium: Calculations

Relationship Between Kp and Kc Example 17-15: Nitrosyl bromide, NOBr, is 34% dissociated by the following reaction at 25oC, in a vessel in which the total pressure is 0.25 atmosphere. What is the value of Kp?

Relationship Between Kp and Kc

Relationship Between Kp and Kc

Relationship Between Kp and Kc

Relationship Between Kp and Kc Example 17-16: Kc is 49 for the following reaction at 450oC. If 1.0 mole of H2 and 1.0 mole of I2 are allowed to reach equilibrium in a 3.0-liter vessel, (a) How many moles of I2 remain unreacted at equilibrium? You do it!

Relationship Between Kp and Kc

Relationship Between Kp and Kc (b) What are the equilibrium partial pressures of H2, I2 and HI? You do it!

Relationship Between Kp and Kc

Relationship Between Kp and Kc (c) What is the total pressure in the reaction vessel? You do it!

Relationship Between Kp and Kc

Relationship Between DGorxn and the Equilibrium Constant Example 17-17: Calculate the equilibrium constant, Kp, for the following reaction at 25oC from thermodynamic data in Appendix K. Note: this is a gas phase reaction.

Relationship Between DGorxn and the Equilibrium Constant

Relationship Between DGorxn and the Equilibrium Constant

Relationship Between DGorxn and the Equilibrium Constant Kp for the reverse reaction at 25oC can be calculated easily, it is the reciprocal of the above reaction.

Relationship Between ΔGorxn and the Equilibrium Constant Example 17-18: At 25oC and 1.00 atmosphere, Kp = 4.3 x 10-13 for the decomposition of NO2. Calculate ΔGorxn at 25oC.

Evaluation of Equilibrium Constants at Different Temperatures Example 17-19: For the reaction in example 17-18, DHo = 114 kJ/mol and Kp = 4.3 x 10-13 at 25oC. Estimate Kp at 250oC.

Evaluation of Equilibrium Constants at Different Temperatures