Exam 1 – Chapter 14– Worksheet 1 Chapter 14 – Chemical equilibrium 1. These data were obtained for the rate constant for reaction of an unknown compound and water: T(°C) 25.0 30.0 56.2 78.2 k( s-1) 7.95 x 10-8 2.37 x 10-7 1.04 x 10-5 1.45 x 10-4 (a) Calculate the activation energy for this reaction. (b) Estimate the rate constant of the reaction at a temperature of 100.0 degrees Celsius. 2. Write the equilibrium constant expression for each reaction a. 2H2O2 (g) ⇌ 2H2O (g) + O2 (g) b. PCl3 (g) + Cl2 (g) ⇌ PCl5 (g) c. SiO2 (s) + 3C(s) ⇌ SiC (s) + 2 CO (g) d. H2 (g) + 1/8 S8 ⇌ H2S (g) e. 4 H3O+ (aq) + 2 Cl- (aq) + MnO2 (s) ⇌ Mn2+ (aq) + 6H2O (l) + Cl2 (aq) 3. Consider these two equilibria involving SO2 (g) and their corresponding equilibrium constants SO2 (g) + ½ O2 (g) ⇌ SO3 (g) Kc1 2SO3 (g) ⇌ 2SO2 (g) + O2 (g) Kc2 How are Kc1 and Kc2 related to one another? Exam 1 – Chapter 14– Worksheet 1 4. Consider the equilibrium 2A (aq) ⇌ B (aq) at equilibrium, [A] = 0.056 M and [B] = 0.21 M. Calculate the equilibrium constant for the reaction as written. 5. Consider the equilibrium at 25 degrees Celsius. 2SO3 (g) ⇌ 2SO2 (g) + O2 (g) Kc =3.58 x 10-3 Suppose that 0.15 mol SO3 (g), 0.015 mol SO2 (g), and 0.0075 mol O2 (g) are placed into a 10.0 L flask at 25 degrees Celsius. Is the system at equilibrium? If not, in which direction must the reaction proceed to reach equilibrium? 6. Hydrogen gas and Iodine gas react via the equation H2 (g) + I2 (g) ⇌ 2HI (g) Kc=76 (at 600K) If 0.050 mol HI is placed in an empty 1.0 L flask at 600 K, what are the equilibrium concentrations of HI, I 2 and H2? 7. The Equilibrium constant Kc for the reaction CO (g) +H2O (g) ⇌ CO2 (g) + H2 (g) has a value of 4.00 at 500K. If a mixture of 1.00 mol CO and 1.00 mol H2O is allowed to come to equilibrium in a flask of volume 1.00L at 500K, (a) Calculate the final concentrations of all four species (b) What would be the equilibrium concentrations if 1.00 mol each of CO and H 2O were added to the flask?