chem_126_2009_Common_2_ANSWERS1122z

chem_126_2009_Common_2_ANSWERS1122z - Chem 126 Exam 2 2009...

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Chem 126 Exam 2 2009 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. Which of the acids in the table is the strongest acid? a. Acetic b. Fluoroacetic c. Formic d. Hydrocyanic e. Hydrofluoric 2. 14 g HNO 3 is diluted to 250 mL. What is the pH? a. 3.05 b. 1.25 c. 0.20 d. 0.05 e. 0.89 3. 50.0 mL of 0.35 M HBr is mixed with 100. mL of 0.09 M HI? What is the pH? a. 0.46 b. 0.75 c. 1.04 d. 0.36 e. 2.63 4. 50.0 mL of 0.50 M HF is mixed with 50. mL of 0.20 M HCl? What is the pH? a. 0.70 b. 0.46 c. 0.93 d. 1.22 e. 1.00 ( 29 Strong acid + strong acid 0.35 50 0.09 100 17.5 ; 9 1 1 26.5 0.177 0.177 ; log log 0.177 0.75 150 mol mL mol mL mmol HBr x mmol mmol HI x mmol L L mmol mol H M pH H mL L + + = = = = = = = = - = - = ( 29 ( 29 ( 29 Strong acid HCl + weak acid HF ; strong acid determines the pH 50 0.20 0.1 log log 0.1 1 100 mL H M M pH H mL + + = = = = - = - = The one with the largest is the strongest. a K ( 29 3 . . 1 14 3 16 63 / 1 14 63 0.89 log log 0.89 0.051 0.25 M W HNO x g mol mol g g mol M M pH H L L + = + + = = = = = - = - =
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Chem 126 Exam 2 2009 5. 75.0 mL of 0.60 M HCl is mixed with 200. mL of 0.20 M Ba(OH) 2 . What is the pH? a. 13.10 b. 0.90 c. 1.74 d. 12.26 e. 10.78 6. What is the pH of a 0.64 M HCN? K a = 4.79 x 10 -10 M. a. 4.60 b. 5.01 c. 4.85 d. 9.51 e. 4.76 7. A 0. 33 M solution of a weak acid, HB, has a pH of 5.35? What is K a ? a. 1.4x10 -5 M b. 4.5x10 -6 M c. 6.0x10 -11 M d. 4.5 x10 -10 M e. 1.4x10 -11 M 8. Which of the following ions is acidic? a. Fe 3+ b. Cl - c. CN - d. SO 4 2- e. Na + ( 29 ( 29 ( 29 2 Acid-base neutralization: 0.60 75 0.2 200 45 ; 2 80 1 1 I 45 80 mol mL mol mL mmol H x mmol mmol OH x mmol L L H aq OH aq H O aq + - + - = = = = + ( 29 C -45 -45 +45 E 0 35 35 0.127 ; log 0.127 0.90; 14 13.10 275 mmol OH M pOH pH pOH mL - = = = - = = - = - - 2- 4 3 3 . . , , . Na
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This note was uploaded on 11/09/2010 for the course CHEM Chem taught by Professor Petrova during the Spring '09 term at NJIT.

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chem_126_2009_Common_2_ANSWERS1122z - Chem 126 Exam 2 2009...

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