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Unformatted text preview: Version 030 – Make up 2 – laude – (51635) 1 This printout should have 20 questions. Multiplechoice 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, 2hydroxyaniline, 3hydroxyaniline, and 4hydroxyaniline. 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. 4hydroxyaniline, 2hydroxyaniline, ani line, 3hydroxyaniline 3. 2hydroxyaniline, 3hydroxyaniline, ani line, 4hydroxyaniline 4. 3hydroxyaniline, aniline, 2hydroxyani line, 4hydroxyaniline correct Version 030 – Make up 2 – laude – (51635) 2 5. 4hydroxyaniline, 3hydroxyaniline, 2 hydroxyaniline, aniline 6. 4hydroxyaniline, aniline, 3hydroxyani line, 2hydroxyaniline 7. aniline, 2hydroxyaniline, 3hydroxyani line, 4hydroxyaniline 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 3hydroxyaniline < aniline < 2hydroxyaniline < 4hydroxyaniline 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.
 Spring '07
 Holcombe

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