exam 2 buffer questions

exam 2 buffer questions - Past buffer and titration...

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Past buffer and titration questions from Sp08 Exam II: 1. Which of the following combinations would be the best to buffer an aqueous solution at a pH of 5.0? (a) H 3 PO 4 and H 2 PO 4 K a1 = 7.5 10 3 (b) HNO 2 and NO 2 K a = 4.5 10 4 (c) CH 3 CO 2 H and CH 3 COO K a = 1.8 10 5 (d) H 2 PO 4 and HPO 4 2 K a2 = 6.2 10 8 (e) NH 4 + and NH 3 K a = 5.7 10 10 2. If you wanted to make a 3 liter solution of 500 mM formic acid buffer at pH 3.9, how many grams each of sodium formate (MW = 68.0 g/mol) and formic acid (MW = 46.0 g/mol) would you add? (See Table for K a values). (a) 98.6 g sodium formate & 2.3 g formic acid (b) 13.8 g sodium formate & 13.6 g formic acid (c) 20.2 g sodium formate & 9.4 g formic acid (d) 41.5 g sodium formate & 40.9 g formic acid (e) 60.5 g sodium formate & 28.1 g formic acid 3. What is the pH of a solution containing 0.20 M benzoic acid (HC 7 H 5 O 2 ) and 0.35 M sodium benzoate (NaC 7 H 5 O 2 )? The pK a of benzoic acid is 4.19.
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exam 2 buffer questions - Past buffer and titration...

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