CHAPTER 15 CONCEPTUAL QUESTIONS

CHAPTER 15 CONCEPTUAL QUESTIONS - CHAPTER 15 CONCEPTUAL...

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Unformatted text preview: CHAPTER 15 CONCEPTUAL QUESTIONS ACID AND BASE CONCEPTS 2. CHEM162-2000 HOURLY EXAM II CHAPTER 14 - ACID AND BASE EQUILIBRIA ACID AND BASE EQUILIBRIA CONCEPTS Which of the following species is/are amphiprotic? X. H 2 CO 3 Y. HCO 3- Z. CO 3 2- A. X and Y only B. Z only C. Y only D. Y and Z only E. X, Y, and Z 13. CHEM162-2000 HOURLY EXAM II CHAPTER 14 - ACID AND BASE EQUILIBRIA ACID AND BASE EQUILIBRIA CONCEPTS Phosphoric acid, H 3 PO 4 , is a polyprotic acid. Which one of the following equations has an equilibrium constant that would be designated as K a2 for phosphoric acid? A. H 3 PO 4 (aq) + H 2 O(l) H 3 O + (aq) + H 2 PO 4- (aq) B. H 2 PO 4- (aq) + H 2 O(l) H 3 O + (aq) + HPO 4 2- (aq) C. H 2 PO 4- (aq) + H 2 O(l) H 3 PO 4 (aq) + OH- (aq) D. H 3 PO 4 (aq) + OH- (aq) H 2 PO 4- (aq) + H 2 O(l) E. HPO 4 2- (aq) + H 2 O(l) H 3 O + (aq) + PO 4 3- (aq) 20. CHEM162-2000 HOURLY EXAM II CHAPTER 14 - ACID AND BASE EQUILIBRIA ACID AND BASE CONCEPTS Which of the following changes will raise the pH of an aqueous solution of butyric acid, CH 3 (CH 2 ) 2 COOH? X. add NaOH Y. add NaCH 3 (CH 2 ) 2 COO Z. add water A. X only B. Y only C. X and Y only D. Z only E. X, Y and Z X. A very simple answer is that if hydroxide is added to any solution, the pH will rise. A more sophisticated answer is to see what happens when OH- is added to a weak acid. HB + OH- HOH + B B- + H 2 O HB + OH- So even though the OH- forms a conjugate base, the conjugate base forms additional OH, so the pH should rise. Y. A very simple answer is that if a weak base is added to any solution, the pH will rise. A more sophisticated answer is to see what happens when B- is added to a weak acid. HB + B- B- + HB Even though there is no net reaction, the addition of B- provided B- concentration that wasn’t there prior to the addition. B- + H 2 O HB + OH- The additional B- forms OH- , which raises the pH. Z. A simple answer is that water will dilute any acid or base concentration, resulting in a final pH closer to 7. Hence, a low pH resulting from a weak acid will rise toward seven with the addition of water. This can be demonstrated by doing a calculation for any weak acid, e.g. acetic acid, which has a K a of 1.8 x 10-5 . If we do the calculation beginning with a concentration of 0.10 M acetic acid, the pH will be 2.8. If we dilute the solution to form a 0.01 M solution of acetic acid, calculation will show that the equilibrium pH will be appreciably higher than 2.8. 21. CHEM162-2000 HOURLY EXAM II CHAPTER 14 - ACID AND BASE EQUILIBRIA ACID AND BASE EQUILIBRIA CONCEPTS Consider two acids: HClO 2 K a = 1.0 x 10-2 HClO K a = 3.0 x 10-8 Which of the following statements is/are true? X. K b for ClO 2- is greater than K b for ClO- ....
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This note was uploaded on 12/22/2011 for the course CHEM 01:160:162 taught by Professor Donaldseigel during the Spring '10 term at Rutgers.

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CHAPTER 15 CONCEPTUAL QUESTIONS - CHAPTER 15 CONCEPTUAL...

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