solution for hw 4 - Chem 211 Solutions to WebCT Homework...

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Unformatted text preview: Chem 211 Solutions to WebCT Homework Chem 211 1. Polyprotic Buffer How many mL of 4.746 M KOH should be added to 0.835 grams of oxalic acid (H 2 C 2 O 4 FW 90.035 g/mol) to give a pH of 3.298 when diluted to 500.0 mL in a volumetric flask? Use the appendix in the text book for values of acid and base dissociation constants. Pay attention to the number of significant figures that are appropriate for your answer. From Appendix G for Oxalic Acid pK a1 = 1.27, K a1 = 5.4 10-2 pK a2 = 4.266, K a1 = 5.42 10-5 At pH = 3.298, the principle species is HC 2 O 4- and the next principle species is C 2 O 4 2- . So we have a buffer consisting of HC 2 O 4- and C 2 O 4 2- . ( ) mmol 27 . 9 mole 1 mmole 1000 g 035 . 90 mole 1 g 835 . O C H mmol Initial 42 4 2 2 = = Chem 211 Solutions to WebCT Homework To produce a buffer consisting of HC 2 O 4- and C 2 O 4 2- , all 9.27 42 mmol of H 2 C 2 O 4 would have been initially converted to HC...
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This note was uploaded on 10/23/2008 for the course CHEM 211 taught by Professor Russianteacher during the Winter '07 term at University of Alberta.

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solution for hw 4 - Chem 211 Solutions to WebCT Homework...

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