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Unformatted text preview: Version 197 Quiz 3 laude (51635) 1 This print-out should have 8 questions. Multiple-choice questions may continue on the next column or page find all choices before answering. 001 5.0 points Which of the following assumptions are made when treating the equation [H + ] = ( K a C a ) 1 / 2 as a good approximation of the proton concentration of a weak acid solution? I) waters contribution to the proton con- centration is negligible II) the percent ionization is low III) [H+] = [A- ] 1. I, III 2. III 3. II, III 4. II 5. I 6. I, II 7. I, II, III correct Explanation: In deriving the equation [H + ] = ( K a C a ) 1 / 2 , we ignore the protons that result from auto- protolysis that makes both statements I and III true, and we also assume that the value of C a is large relative to the change in the concentration of the acid. In other words, we assume that the percent ioniation is low, so statement II is true....
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This note was uploaded on 05/02/2011 for the course CH 302 taught by Professor Holcombe during the Spring '07 term at University of Texas at Austin.
- Spring '07