chem_126_2010_Common_2_ANSWERS1122z12

chem_126_2010_Common_2_ANSWERS1122z12 - Chem 126 Exam 2...

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Unformatted text preview: Chem 126 Exam 2 March 26, 2010 Ellis NONE OF THE MULTIPLE CHOICE PROBLEMS REQUIRES EXTENSIVE OR TIME COMSUMING CALCULATIONS. IF YOUR METHOD REQUIRES EXTENSTIVE CALCULATIONS IT IS EITHER WRONG OR HARDER THAN WHAT IS REQUIRED. 1. A 0.1 M solution of each acid in the table is prepared. Which has the HIGHEST pH. Careful. a. Acetic b. Fluoroacetic c. Formic d. Hydrocyanic e. Hydrofluoric 2. 2.5 g NaOH is diluted to 5.0 L. What is the pH? a. 1.90 b. 12.1 c. 0.30 d. 13.7 e. 13.17 3. 100.0 mL of 0.45 M HNO 3 is mixed with 200. mL of 0.55 M HCN? What is the pH? a. 0.00 b. 0.26 c. 0.35 d. 0.48 e. 0.82 4. 60.0 mL of 0.30 M HNO 3 is mixed with 40. mL of 0.20 M HCl? What is the pH? a. 0.74 b. 0.59 c. 0.93 d. 1.10 e. 0.52 ( 29 3 Strong acid + strong acid 0.3 60 0.20 40 18 ; 8 1 1 18 8 0.26 0.26 ; log log 0.26 0.59 100 mol mL mol mL mmol HNO x mmol mmol HCl x mmol L L mmol mol H M pH H mL L + + = = = = + = = = = - = - = ( 29 ( 29 ( 29 Strong acid HCl + weak acid HCN ; strong acid determines the pH 100 0.45 0.15 log log 0.15 0.82 300 mL H M M pH H mL + + = = = = - = - = The highest pH means the least acidic or the one with the smallest . (Most acidic or lowest pH has largest .) a a K K ( 29 . . 23 16 1 40 / 1 2.5 40 0.0125 log log 0.0125 1.90 5 14 12.10 M W NaOH g mol mol g g mol M M pOH OH L L pH pOH- = + + = = = = = - = - = =- = Chem 126 Exam 2 March 26, 2010 Ellis 5. 15.0 mL of 0.62 M HCl is mixed with 80. mL of 0.10 M KOH. What is the pH? a. 1.86 b. 1.79 c. 1.06 d. 1.01 e. >10 6. What is the hydrogen ion concentration of a 0.77 M HF? K a = 6.76 x 10-4 M. a. < 0.01 M b. 0.011 M c. 0.022 M d. 0.68 M e. 0.77 M 7. A 0.0019 M solution of a weak acid, HB, has a pH of 3.30. What is K a ? a. 1.8x10-4 M b. 1.3x10-4 M c. 2.5x10-7 M d. >10-2 M e. <10-8 M 8. Which of the following ions is neutral? a. Al 3+ b. Br- c. F- d. NH 4 + e. CBr 3 COO- ( 29 ( 29 ( 29 2 Acid-base neutralization: 0.62 15 0.1 80 9.3 ; 8 1 1 I 9.3 8 mol mL mol mL mmol H x mmol mmol OH x mmol L L H aq OH aq H O aq +- +- = = = = + ( 29 C -8 -8 +8 E 1.3 1.3 0.0137 ; log 0.0137 1.86 95 mmol H M pH mL + = = = - = -- 3 3 4 (- - )....
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chem_126_2010_Common_2_ANSWERS1122z12 - Chem 126 Exam 2...

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