Chem 122 Exam 4 Questions for Saturday Morning Review Spring 2022 R Hatfield L Schroeder and E Stec 1 Calculate the pH pOH H3O and OH for each sample at 25 C State if the solution is acidic or basic a Gastric juice in a person s stomach with pH of 2 100 pOH 11 900 OH 1 26 10 12 H3O 7 94 10 3 acidic solution b A 0 030 M lithium hydroxide solution OH 0 030 pOH 1 52 pH 12 48 H3O 3 31 10 13 basic solution 2 Give the missing conjugate in the pairs of conjugate acids bases Base HS AsO Acid HPO PH 3 Anions containing hydrogen for example H2PO4 usually show amphiprotic behavior Write equations illustrating the amphiprotism of this anion 4 You are given four weak acids Which substance is the strongest acid HW Ka 2 9 10 4 HX pKa 2 6 HY Ka 1 3 10 5 HZ pKa 9 7 5 Which acid has the strongest conjugate base HNO2 pKa 3 34 HClO pKa 7 54 HBrO pKa 8 55 6 Place the species in each of the following groups in order of increasing acid strength Explain the order you chose for each group a H2SeO3 H2TeO3 b H2S H2Se c HOCl HOI d HBrO2 HBrO3 7 Predict if the pH of a solution of the following salts would be acid basic neutral You may need to look up or otherwise determine Ka and Kb values a KBr b NaHCO3 c NH4CN d Al NO3 3 e LiClO2 8 Arrange the following 0 10 M solutions in order of most acidic to most basic KOH KNO3 KCN NH4Cl HCl 9 Acrylic acid CH2 CHCOOH is a precursor for many important plastics Ka for acrylic acid is 5 6 10 5 a Calculate the pH of a 0 25 M solution of acrylic acid 2 43 b Calculate the percent dissociation of a 0 25 M solution of acrylic acid 1 5 c Calculate the pH of a 0 050 M solution of sodium acrylate NaC3H3O2 8 48 10 Trichloroacetic acid CCl3COOH is a corrosive acid that is used to precipitate proteins The pH of a 0 050 M solution of trichloroacetic acid is the same as the pH of a 3 7 10 4 M HClO4 solution Calculate Ka for trichloroacetic acid 2 7 10 6 11 Calculate OH H3O and the pH of a 0 015 M aqueous solution of p toluidine CH3C6H4NH2 pKb for CH3C6H4NH2 is 8 92 OH 4 2 10 6 pH 8 63 H3O 2 4 10 9 12 Which of the following can be classified as buffer solutions a 0 25M HBr 0 25M HOBr b 0 15M HClO4 0 20M RbOH c 0 50M HOCl 0 35M KOCl d 0 60M KOH 0 70M NH3 e 0 85M CH3NH2 0 60M CH3NH3NO3 c e 13 Calculate the pH a Of a buffer that is 0 095 M in HCHO and 0 120 M in KCHO The Ka of Formic acid is 1 8 x 10 4 3 84 b after the addition of 0 020 mol HCl to 1 L of this buffer 3 68 b after the addition of 0 020 mol NaOH to 1 L of this buffer 4 02 14 Which acid would you choose to combine with its sodium salt to make a buffer of pH 3 40 chlorous acid HClO2 pKa 1 95 formic acid HCHO2 pKa 3 74 nitrous acid HNO2 pKa 3 34 hypochlorous acid HClO pKa 7 54