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Homework1 - and the pH of the solution 5 Distilled water in...

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BMB 461 Fall Semester 2009 Optional Homework Assignment #1 Key will be posted on Thursday, September 10th Note : most of the K a and p K a values needed to solve these problems can be found in your notes or in the text. 1.) Sketch the hydrogen-bonded structures that may be formed between water and a) methanol, CH 3 OH; b) acetone; c) backbone groups on a peptide chain. 2.) Explain the forces that drive certain lipids to form micelles when mixed with water. 3.) Calculate the concentrations of all molecular and ionic species and the pH in aqueous solutions that have the following formal compositions: a) 0.01 M acetic acid; b) 0.25 M ammonium chloride; c) 0.05 M acetic acid + 0.1 M sodium acetate; d) 0.2 M boric acid + 0.05 M sodium borate (p K a of boric acid = 9.24); e) 0.5 M hydrochloric acid. 4.) The formal composition of an aqueous solution is 0.08 M K 2 HPO 4 + 0.12 M KH 2 PO 4 . Calculate the concentrations of all ionic and molecular species in the solution
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Unformatted text preview: and the pH of the solution. 5.) Distilled water in equilibrium with air contains dissolved carbon dioxide at a concentration of 1.0 x 10-5 M. Calculate the pH of such a solution. 6.) Calculate the formal concentrations of acetic acid and sodium acetate necessary to prepare a buffer solution of pH 5.5 that is 0.2 M in total acetate. Extra Challenge Problem 7.) An enzymatic reaction takes place in a 10-mL solution that has a total citrate concentration of 120 mM and an initial pH of 7.00. During the reaction, 0.2 millimoles of acid (H + ) are produced. Calculate the final pH of the solution. What would the final pH of the solution be in the absence of the citrate buffer assuming that the other components of the solution have no significant buffering capacity and that the solution is initially at pH 7? Citrate p K a s = 3.13, 4.76, and 6.40....
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