Quiz 6-solutions - Version 091 Quiz 6 fakhreddine (51615)...

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Version 091 – Quiz 6 – fakhreddine – (51615) 1 This print-out should have 5 questions. Multiple-choice questions may continue on the next column or page – Fnd all choices before answering. 001 2.0 points A solution is prepared by mixing 250 mL of 1.00 M CH 3 COOH with 500 mL of 1.00 M NaCH 3 COO. What is the pH of this solution? ( K a for CH 3 COOH = 1 . 8 × 10 - 5 ) 1. 4.44 2. 5.36 3. 4.74 4. 4.58 5. 5.05 correct Explanation: V CH 3 COOH = 250 mL [CH 3 COOH] = 1.00 M V NaCH 3 COO = 500 mL [NaCH 3 COO] = 1.00 M [CH 3 COOH] = 250 mmol 750 mL [CH 3 COO - ] = 500 mmol 750 mL pH = p K a + log [CH 3 COO - ] [CH 3 COOH] = - log(1 . 8 × 10 - 5 ) + log p 500 250 P = 5 . 04576 002 2.0 points A bu±er is formed by mixing 100 mL of 0.1 M NH 4 Cl with 50 mL of 0.3 M NH 3 . To this solution 19 mL of 0 . 1 M NaOH is added. What is the approximate pH of the new so- lution after neutralization? Assume a K b of 1 . 8 × 10 - 5 for the weak base. 1.
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This note was uploaded on 05/19/2011 for the course CHEM 51615 taught by Professor Fatima during the Spring '11 term at University of Texas at Austin.

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Quiz 6-solutions - Version 091 Quiz 6 fakhreddine (51615)...

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