Make up 2-solutions

Make up 2-solutions - Version 030 – Make up 2 – laude...

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Unformatted text preview: Version 030 – Make up 2 – laude – (51635) 1 This print-out should have 20 questions. Multiple-choice questions may continue on the next column or page – find all choices before answering. 001 6.0 points Which of the following compounds has the LOWEST molar solubility in water? 1. Al(OH) 3 , K sp = 2 × 10- 32 2. PbSO 4 , K sp = 1 . 3 × 10- 8 3. CdS, K sp = 1 . × 10- 28 correct 4. MgC 2 O 4 , K sp = 8 . 6 × 10- 5 5. Sn(OH) 2 , K sp = 3 × 10- 27 Explanation: 002 6.0 points A 40 mL sample of 0 . 25 M NaCHOO is titrated with 0 . 2 M HCl. What is the pH of the solution after 140 mL of HCl has been added? 1.-1.0 2. 3. 2.0 4. 2.1 5. 3.0 6. 1.0 correct Explanation: After the CHOOH has been neutralized, . 018 mol of HCl remain in a solution with a total volume of 180 mL . [H + ] = . 018 mol 180 mL = 0 . 1 M pH = 1 003 6.0 points Which of the following equations does not require any assumptions in order to provide an accurate solution? 1. [H + ] = ( K a · C a ) 1 / 2 2. [OH- ] = K b · parenleftbigg C b C a parenrightbigg 3. [OH- ] = ( K b · C b ) 1 / 2 4. all require assumptions correct 5. [H + ] = C a Explanation: All of these equation assume, at the very least, that autoprotolysis is negligible. 004 6.0 points Consider the bases (from left to right below) aniline, 2-hydroxyaniline, 3-hydroxyaniline, and 4-hydroxyaniline. The p K a value for the conjugate acid of each base is below the structure. NH 2 OH NH 2 OH NH 2 OH NH 2 4 . 63 4 . 72 4 . 17 5 . 47 Arrange the bases in order of increasing strength. 1. None of these 2. 4-hydroxyaniline, 2-hydroxyaniline, ani- line, 3-hydroxyaniline 3. 2-hydroxyaniline, 3-hydroxyaniline, ani- line, 4-hydroxyaniline 4. 3-hydroxyaniline, aniline, 2-hydroxyani- line, 4-hydroxyaniline correct Version 030 – Make up 2 – laude – (51635) 2 5. 4-hydroxyaniline, 3-hydroxyaniline, 2- hydroxyaniline, aniline 6. 4-hydroxyaniline, aniline, 3-hydroxyani- line, 2-hydroxyaniline 7. aniline, 2-hydroxyaniline, 3-hydroxyani- line, 4-hydroxyaniline Explanation: p K a + p K b = 14 The higher the value of p K a of an acid, the lower the value of p K b for the corresponding conjugate base. The lower the value of p K b the stronger the base; therefore the order is 3-hydroxyaniline < aniline < 2-hydroxyaniline < 4-hydroxyaniline No simpler pattern exists, but the position of the- OH group does affect the basicity....
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This note was uploaded on 05/02/2011 for the course CH 302 taught by Professor Holcombe during the Spring '07 term at University of Texas.

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Make up 2-solutions - Version 030 – Make up 2 – laude...

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