Equilibrium Acid Base Review 1. Hypochlorous acid may be produced by the following reaction H 2O(g) + Cl 2O(g) 2 HOCl (g) Kc = 0.

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1 Equilibrium Acid Base Review 1. Hypochlorous acid may be produced by the following reaction H 2O(g) + Cl 2O(g) 2 HOCl (g) Kc = Determine the concentrations of each reagent at equilibrium at 25 C if the initial concentrations of both water vapour and chlorine monoxide were 4.00 mol/l. 2.. Consider the following equilibrium CO(g) + H 2O(l) CO 2(g) + H 2(g) Kc = 5.0 at 650 C In a rigid 1.00 L laboratory reaction vessel, a technician places 1.00 mol of each of the four substances involved in this equilibrium. The vessel is heated to 650 C. Determine the equilibrium amount concentrations of each substance, organizing your values in an ICE table. (Hint: use the value of Kc to determine which side of the reaction is favored, and therefore which substances will increase and which substances will decrease as equilibrium is established.) 3. Consider the reaction N 2(g) +3 H 2(g) 2 NH 3(g), at equilibrium. If the system container volume were to be suddenly decreased, the concentration of nitrogen gas in the system would immediately A. increase, then decrease to a new constant value B. remain unchanged, because the reaction is at equilibrium C. increase, then remain steady at a new constant value D. decrease, then remain steady at a new constant value

2 Carbon monoxide gas and oxygen gas react to form carbon dioxide gas as represented by the equilibrium equation below. 2 CO(g) + O 2 (g)! 2 CO 2 (g) 4a) Write the equilibrium law expression for this reaction. (1 mark) A technician added carbon monoxide gas and oxygen gas to an empty flask. The technician then recorded the concentrations of each gas present in the flask until the reaction reached equilibrium at 500 K, as shown in the graph below. b) Calculate the value of the equilibrium constant (Kc) for this reaction at 500K. (2 marks) c) Are the products or reactants favored for this reaction? Justify your answer. (1 mark) d) Use Modified Hess s Law to calculate the enthalpy change for this reaction. (1 mark) e) How will the position of the equilibrium be affected by an increase in temperature? Justify your answer. (1 mark) f) How will the value of the equilibrium constant be affected by in increase in the temperature. Justify your answer. (1 mark)

3 Use the following information to answer question 2. Methane gas can be produced in a laboratory by reacting carbon disulfide, CS 2 (g), and hydrogen gas, as represented by the equation below. CS 2 (g) + 4 H 2 (g)! CH 4 (g) + 2 H 2 S(g) The initial concentrations that are placed into an empty flask at a temperature of 90.0 C are mol/l CS 2 (g) and mol/l H 2 (g). When equilibrium is established, mol/l CS 2 (g) is present. 6a. Determine the concentration of hydrogen gas present in the flask at equilibrium. (2 marks) b) Write the equilibrium law expression for the reaction, and determine the equilibrium constant for the reaction at 90.0 C. (2 marks) c) Identify and describe three stresses that could be applied to the system that would shift the equilibrium to the right. (3 marks) concentration of reactants and products (mol/l) d) Draw a graph showing the change in the concentration of the reactants and products as equilibrium is established. point at which EQ is established time

4 Use the following information to answer the next question. 7. For each point in time, indicate shift in equilibrium, and then suggest a stress applied to the system that could account for the change. Time Equilibrium Shift (left or Right) Stress that explains the EQ Shift W Y Z 8. Write chemical formulas and net ionic equations for the following overall reactions. (a) Vinegar is used to neutralize a drain cleaner spill. (drain cleaner is sodium hydroxide b) the addition of a small amount of a strong acid to a hydrogen phosphate ion phosphate ion buffer solution c) the addition of phenolphthalein indicator to a strong base d) sodium sulfate is dissolved in water e) Baking soda solution (sodium hydrogen carbonate) is used to neutralize spilled rust remover containing oxalic acid.

5 9. Hypochlorous acid may be produced by the following reaction H 2O(g) + Cl 2O(g) 2 HOCl (g) Kc = Determine the concentrations of each reagent at equilibrium at 25 C if the initial concentrations of both water vapour and chlorine monoxide were 4.00 mol/l. 10. A 0.10 mol/l solution of the essential amino acid tryptophan has a measured ph of 5.19 at 25 C. Predict the percent ionization of this tryptophan solution, and the Ka value for aqueous tryptophan. The molecular formula for tryptophan may be written as C 10H 11N 2COOH. 11. A mol/l laboratory solution of sodium propanoate, NaC 2H 5COO(aq), has a measured ph of 8.95 at 25 C. Calculate Kb for the propanoate ion.