Chemical Equilibrium

The following problems are taken from T. L. Brown, H. E. Lemay, B. E. Bursten, & J. R. Burdge, Chemistry: The Central Science, Ninth Edition, Chapter 15.

12) The equilibrium constant for the reaction

       2NO(g) + Br₂(g) 2NOBr(g)

       is K_eq = 1.3 x 10^-2 at 1000 K..

       (a) Calculate K_eq for 2NOBr(g) 2NO(g) + Br₂(g)

       (b) At this temperature does the equilibrium favor NO and Br₂, or does it favor NOBr?

14) Consider the following equilibrium, for which K_eq = 0.0752 at 480°C:

       2Cl₂(g) + 2H₂O(g) 4HCl(g) + O₂(g)

      (a) What is the value of K_eq for the reaction 4HCl(g) + O₂(g) 2Cl₂(g) + 2H₂O(g)?

      (b) What is the value of K_eq for the reaction Cl₂(g) + H₂O(g)2HCl(g) + 1/2O₂(g)?

      (c) What is the value of K_eq for the reaction 2HCl(g) + 1/2O₂(g)Cl₂(g) + H₂O(g)?

22) Phosphorus trichloride gas and chlorine gas react to form phosphorus pentachloride gas:

      PCl₃(g) + Cl₂(g) PCl₅(g)

      A gas vessel is charged with a mixture of PCl₃(g) and Cl₂(g), which is allowed to equilibrate at 450 K. At equilibrium the partial pressures of the three gases are P_PCl3 = 0.124 atm, P_Cl2 = 0.157 atm, and P_PCl5 = 0.130 atm.

      (a) What is the value of K_eq at this temperature?

      (b) Does the equilibrium favor reactants or products?

    
24) A mixture of 1.374 g of H₂ and 70.31 g of Br₂ is heated in a 2.00-L vessel at 700 K. These substances react as follows:       

      H₂(g) + Br₂(g) 2HBr(g)

      At equilibrium the vessel is found to contain 0.566 g of H₂.

      (a) Calculate the equilibrium partial pressures of H₂, Br₂, and HBr.

      (b) Calculate K_eq.

32) At 900 K the following reaction has K_eq = 0.345:

      2SO₂(g) + O₂(g)   2SO₃(g)

      In an equilibrium mixture the partial pressures of SO₂ and O₂ are 0.165 atm and 0.755 atm, respectively. What is the equilibrium partial pressure of SO₃ in the mixture?

38) At 21.8°C, K_eq = 7.0 x 10^-2 for the equilibrium

      NH₄HS(s) NH₃(g) + H₂S(g)

      Calculate the equilibrium partial pressures of NH₃ and H₂S if a sample of solid NH₄HS is placed in a closed vessel and decomposes until equilibrium is reached.