Chapter 7 Mixtures of Acids Bases THE COMMON ION EFFECT AND BUFFERS 1 What is a common ion and what is the common ion effect 2 Why can the dissociation of a weak base be ignored when calculating the pH of a solution that contains both a weak base and a strong base 3 What is a buffer and how does it function 4 Explain why the terms appreciable and comparable appear in the definition of a buffer 5 Why is a solution that is 1 4 mM HF and 6 4 mM KF not a good buffer 6 Why is a solution that is 1 3 M HF and 1 3 mM KF not a good buffer 7 Explain why a solution of a strong acid and its conjugate base is not a buffer Use a solution of HCl and KCl as an example buffered solution a pH 1 5 a pH 3 5 8 Explain why a solution that is prepared by dissolving 0 1 mol of each of KH2PO4 and K3PO4 in 1 L of water is not a 9 Use Appendix C to determine the best acid base pair to prepare buffers at the following pH s 10 Select an acid base pair from Appendix C that could be used to buffer a solution at each of the following pH s b pH 7 0 b pH 8 0 c pH 12 0 c pH 10 6 11 What is the pH of a solution that is 0 16 M NH3 and 0 43 M NH4Cl 12 What is the pH of a solution that is 0 21 M K2HPO4 and 0 096 M K3PO4 13 What is the pH of a solution made by dissolving 7 6 g KNO2 to 750 mL of 0 11 M HNO2 14 What is the pH of a solution made by dissolving 8 5 g of K2CO3 and 6 9 g KHCO3 in 500 mL of water 15 How many grams of potassium acetate must be added to 2 5 L of 0 250 M acetic acid to prepare a pH 4 26 buffer 16 How many grams of ammonium chloride must be added to 0 75 L of 1 2 M ammonia to prepare a pH 10 18 buffer 17 How many milliliters of 6 0 M NaOH must be added to 0 50 L of 0 20 M HNO2 to prepare a pH 3 86 buffer 18 How many milliliters of 3 5 M HCl must be added to 3 8 L of 0 18 M K2HPO4 to prepare a pH 7 42 buffer 1 CN1 a NH3 aq HCN aq NH4 b S2 HCN aq cid 85 HS1 CN1 c F1 HCN aq cid 85 HF aq CN1 EQUILIBRIUM CONSTANTS FOR ACID BASE REACTIONS 19 Use the data in Appendix C to determine the equilibrium constants for the following reactions 20 Use the data in Appendix C to determine the equilibrium constants for the following reactions a NH3 aq H3O1 cid 85 NH4 b F1 H2O cid 85 HF aq OH1 c HSO3 1 HS1 cid 85 H2S aq SO3 1 H2O 2 MIXING PROBLEMS 2 in a solution prepared by mixing 25 0 mL of 0 100 M H2CO3 and 25 0 mL of 0 100 M K2SO3 21 What is SO3 22 What is HOCl in a solution prepared by mixing 50 0 mL of 0 160 M KOCl and 50 0 mL of 0 160 M NH4Cl 23 What is F1 in a solution prepared by mixing 25 mL of 0 16 M HF and 42 mL of 0 086 M KCN 1 prepared by mixing 75 mL of 0 34 M ammonia and 85 mL of 0 18 M acetic acid 24 What is NH4 25 What is the pH of a solution made by mixing 5 0 mL of 1 2 M HCl and 3 0 mL of 0 88 M HBr 26 What is the pH of a solution prepared by mixing 39 mL of 0 074 M Ba OH 2 and 57 mL of 0 11 M KOH 27 What is the pH of a solution prepared by mixing 5 00 mL of 1 20 M HCl and 4 60 mL of 0 840 M NaOH 28 What is the pH of a solution prepared by mixing 38 64 mL of 0 8862 M HCl and 53 66 mL of 0 7500 M NaOH Chapter 7 Mixtures of Acids Bases 29 Calculate the pH change that results when 10 mL of 3 0 M NaOH is added to 500 mL of each of the following solutions a pure water d a solution that is 0 10 M in each CH3COO1 and CH3COOH b 0 10 M CH3COO1 c 0 10 M CH3COOH a pure water b 0 10 M NH4Cl d a solution that is 0 10 M in each NH4 30 Calculate the pH change that results when 10 mL of 3 0 M HCl is added to 500 mL of each of the solutions in Ex 29 31 Calculate the pH change that results when 10 mL of 6 0 M HCl is added to 750 mL of each of the following solutions 32 Calculate the pH change that results when 10 mL of 6 0 M NaOH is added to each of the solutions described in Ex 31 TITRATIONS 33 Sketch the titration curve for the titration of 50 mL of 0 1 M HA Ka 10 7 with 0 1 M NaOH What are the initial pH c 0 10 M NH3 1 and NH3 the pH at the midpoint of the titration and the pH at the equivalence point 34 Sketch the titration curve for the titration of 50 mL of 0 1 M A1 Kb 10 7 with 0 1 M HCl What are the initial pH the pH at the midpoint of the titration and the pH at the equivalence point 35 What is the pH at each equivalence point in the titration of 25 mL of 0 080 M H3PO4 with 0 065 M NaOH 36 What is the pH s at each equivalence points in the titration of 25 mL of 0 080 M H2CO3 with 0 10 M NaOH 37 Consider the titration of 35 0 mL of 0 122 M ammonia with 0 0774 M HCl 38 The CO2 we breathe reacts with water in our blood to form the weak acid H2CO3 What mole ratio of H2CO3 HCO3 a How many mL of HCl are required to reach the equivalence point b What is the pH at the equivalence point What indicator should be used for this titration c What is the pH of the solution after addition of 15 0 mL of acid d What is the pH of the solution after the addition of 65 0 mL of acid 1 is required to obtain a pH of 7 40 the pH of blood Use Ka 4 4x10 8 for H2CO3 39 50 0 ml of 0 10 M HCl are required to titrate 10 0 ml of ammonia window cleaner to the end point 40 …