Please help with question 20 and 30. Explanations and details would be greatly appreciated!! Thank you
29. The hexaprotic acid ethylenediaminetetraacetic acid (EDTA) is widely used in complexation reactions with metal ions. It is frequently used for titrations of Ca2 and Mg" ions in water as a measurement of water hardness. In order to observe typical titration behavior at the equivalence point, the pH of the solution must be buffered so that most of the EDTA exists in solution in the fully deprotonated form. Given the information about EDTA below, choose a pH value for optimal titration. Consult a table of acid dissociation constants to choose a buffer that can provide the necessary pH for titration HOOCH,C+H H2 H2 +H CH COOH 0.0 1.5 3 2.00 4 2.69 5 6.13 6 10.37 HOOCH2C CH2COOH EDTA: HY 30. Consider cis-Butenedioie acid (Maleic Acid, pK.-1.92, pK. 6.27), Sketch the distribution graph for solution containing 0.01 M this weak acid. Label the lines with the respective species to tell them apart. Circle the regions on the graph where Maleic Acid would be a good buffer. Explain why it is in these pH regions that Maleic Acid is a good buffer. Maleic Acid 0.010 0.008 0.006 conc, M 0.004 0.002 6 pH 8 10 12 The Buffer Zone 2/21/09 10