Exam-2A - Fall 2008 CHEMISTRY 104 Section 001 Exam 2 Name:...

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Fall 2008 CHEMISTRY 104 Section 001 Exam 2 Name: ________________________ ID: ________ Seat #: ______ 1. Calculate the concentration of chromate ion, , in a saturated solution of CaCrO 4 . ( K sp = 7.11 × 10 -4 ) A) 2.67 × 10 -2 M B) 1.42 × 10 -3 M C) 7.11 × 10 -4 M D) 5.06 × 10 -7 M E) 3.56 × 10 -4 M 2. In the titration of a weak acid, HA, with a sodium hydroxide solution the stoichiometric point occurs at pH = 9.5. Which of the following weak acid indicators would be best suited to mark the endpoint of this titration? A) indicator A, K a = 10 –11 B) indicator B, K a = 10 –13 C) indicator C, K a = 10 –9 D) indicator D, K a = 10 –7 3. The molar solubility of PbI 2 is 1.48 × 10 -3 M. Calculate the value of K sp for PbI 2 . A) 3.24 × 10 -9 B) 4.38 × 10 -6 C) 1.30 × 10 -8 D) 1.48 × 10 -3 E) none of these 4. A certain indicator HIn has a p K a of 9.00 and a color change becomes visible when 7.00 % of it is In - . At what pH is this color change visible? A) 10.2 B) 3.85 C) 6.15 D) 7.88 E) none of these Page 1
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Use the following to answer question 5. You have two buffered solutions. Buffered solution 1 consists of 5.0 M HOAc and 5.0 M NaOAc; buffered solution 2 is made of 0.050 M HOAc and 0.050 M NaOAc. 5. How do the pHs of the buffered solutions compare? A) The pH of buffered solution 1 is greater than that of buffered solution 2. B) The pH of buffered solution 2 is greater than that of buffered solution 1. C) The pH of buffered solution 1 is equal to that of buffered solution 2. D) Cannot be determined without the K a values. E) None of these (a-d). 6. When 1.7 × 10 -2 mol of nicotinic acid (a monoprotic acid) is dissolved in 350 mL of water, the pH is 3.05. Calculate the K a of nicotinic acid. A) 1.9 × 10 -2 B) 1.7 × 10 -5 C) 4.8 × 10 -2 D) 4.9 × 10 -5 E) none of these Use the following to answer question 7. The following questions refer to the following system: 500.0 mL of 0.020 M Mn(NO 3 ) 2 are mixed with 1.0 L of 1.0 M Na 2 C 2 O 4 . The oxalate ion, C 2 O 4 , acts as a ligand to form a complex ion with the Mn 2+ ion with a coordination number of two.
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This note was uploaded on 11/30/2008 for the course CHEM 104 taught by Professor Quigley during the Spring '08 term at CUNY Hunter.

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Exam-2A - Fall 2008 CHEMISTRY 104 Section 001 Exam 2 Name:...

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