Chapter 17. Equilibrium: The Extent of Chemical Reactions

  • 17.1The Equilibrium State and the Equilibrium Constant
  • 17.2The Reaction Quotient and the Equilibrium Constant
  • The Changing Value of the Reaction Quotient
  • Writing the Reaction Quotient (Q)
  • 17.3Expressing Equilibria with Pressure Terms: Relation between Kc and Kp
  • 17.4Comparing Q and K to Determine Reaction Direction
  • 17.5How to Solve Equilibrium Problems
  • Using Quantities to Find K
  • Using K to Find Quantities
  • Problems Involving Mixtures of Reactants and Products
  • 17.6Reaction Conditions and Equilibrium: Le Châtelier's Principle
  • Change in Concentration
  • Change in Pressure (Volume)
  • Change in Temperature
  • Lack of Effect of a Catalyst
  • Synthesis of Ammonia

Concepts and Skills to Review Before You Study This Chapter

  1. reversibility of reactions (Section 4.7)
  1. equilibrium vapor pressure (Section 12.2)
  1. equilibrium nature of a saturated solution (Section 13.4)
  1. dependence of rate on concentration (Sections 16.2 and 16.5)
  1. rate laws for elementary reactions (Section 16.6)
  1. function of a catalyst (Section 16.7)

1) N2(g) + 3 H2(g)  2 NH3(g) + heat

1. Stress : increase [NH3] N2(g) + 3 H2(g)  2 NH3(g) + heat

2. Stress : increase temp N2(g) + 3 H2(g)  2 NH3(g) + heat

Note : delta T will change K value

3. Stress : decrease the volume N2(g) + 3 H2(g)  2 NH3(g) + heat

4. Stress : add inert gas N2(g) + 3 H2(g)  2 NH3(g) + heat

2)2 SO2(g) + O2(g)2 SO3(g) Given the equilibrium concentrations of SO3: 0.120M SO2: 0.860M O2: 0.330M, calculate the value of Kc for this reaction.

3) For the reaction system, 2 SO2(g) + O2(g)2 SO3(g), Kc has a value of 4.62 at 450.0 K. A system, at equilibrium has the following concentrations: [SO3] = 0.254 M, [O2] = 0.00855 M. What is the equilibrium concentration of SO2?

4) The equilibrium constant for the reaction, H2(g) + I2(g)2 HI(g) is 54.9 at 699.0 K. What is

the equilibrium constant for 4 HI(g) 2 H2(g) + 2 I2(g) under the same conditions?

5) Using this data, 2 NO(g) + Cl2(g) 2 NOCl(g) Kc = 3.20 x 10-3

2 NO2(g) 2 NO(g) + O2(g) Kc = 15.5

calculate a value for Kc for NOCl(g) + ½ O2(g) NO2(g) + ½ Cl2(g).

6) H2(g) + I2(g) <--> 2HI(g) 0.00500mol of H2 and 0.0100mol of I2 is placed in a 5.00L container at 448C. At eq.,[HI] = 0.00187M. Setup ICE table to calculate K.

7) A study of the system, 4 NH3(g) + 7 O2(g)2 N2O4(g) + 6 H2O(g), was carried out. A system was prepared with [NH3] = [O2] = 3.60 M as the only components initially. At equilibrium, [N2O4] is 0.60 M. Calculate the equilibrium concentration of O2.

8) Predict the direction of the reaction?

N2(g) + 3 H2(g) <--> 2 NH3(g) K = 0.060 L^2 / mol^2 at 500.C

initial [NH3] = 0.0010M initial [N2] = 0.000010M initial [H2] = 0.0020M

9) At 25°C, the equilibrium constant Kc for the reaction, 2A(g) B(g) + C(g), is 0.035. A mixture of 8.00 moles of B and 12.00 moles of C in a 20.0 L container is allowed to come to equilibrium. What is the equilibrium concentration of A?

10) What are [ ]eq of each ?

CO(g) + H2O(g) <--> CO2(g) + H2(g) Kc = 5.10 at 700.K

[ ]initial = 1.00M for all 4 species

11) If 2.00M HF dissociates 1.3% in water, what is the K for HF(aq) + H2O(l)  H3O+ (aq) + F- (aq)?