107-2006_EXAM2-WEB

107-2006_EXAM2-WEB - BIOCHEM 107 EXAM II(TOEWS& SANCAR...

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Unformatted text preview: BIOCHEM 107 EXAM II (TOEWS & SANCAR) 10/2/2006 Read each question below very carefully and then mark the one most correct answer on your answer sheet. Sign both your exam and answer sheet and turn both of them in when finished. 1. Acetic acid (CH 3 COOH): a) is a weak acid b) is a strong acid c) is a strong base d) is a good proton acceptor e) c and d are both correct 2. According to Johannes Brønsted and Joseph Lowry, not to mention Dr. Arrel D. Toews, bases are best defined as: a) caustic compounds that feel slippery on your fingers and make good drain cleaners b) compounds that dissociate into a metal cation and the OH- anion c) electron acceptors d) proton acceptors e) proton donors 3. If the pOH of a solution is 9.0, then [H + ] must be: a) [H + ] = [OH-] = 10-7 M b) 10-9 M c) 5.0 d) 9 x 10-14 M e) 10-5 M 4. When the pH of 0.5 L of a solution changes from 9.0 to 3.0: a) the hydrogen ion concentration decreases by a factor of 10 6 b) the hydrogen ion concentration becomes 1,000,000 times higher c) the solution becomes much more basic d) [OH- ] increases 60-fold e) a and c are both correct 5. If 1 mL of 10 M NaOH is added to 1 L of pure water, the pH will: a) be about 10 b) be about 1 c) go down about 5 units d) go up about 5 units e) be about 1 x 10-10 M 6. [H + ] in the stomach is about 6 x 10-2 M. This means the stomach contents: a) are quite acidic b) are very slightly acidic c) are very slightly basic d) are very basic e) have a pH somewhere between 5 and 6 7. The CO 2 /carbonic acid/bicarbonate buffer system helps buffer the blood. The pKa for the carbonic acid/bicarbonate dissociation is 6.10. What’s the pH when carbonic acid = 2.3 mM and bicarbonate = 29.6 mM? a) 4.99 b) 10-6.10 c) 7.21 d) 6.10 e) 10-4.99 The titration curve for phosphoric acid (H 3 PO 4 ) is shown at right. The three pK a values are 2.42, 7.21, and 12.67. 8. The predominant species present at point c is: a) mostly H 3 PO 4 b) mostly PO 4-3 c) mostly H 2 PO 4- d) mostly HPO 4-2 e) a mix of H 2 PO 4- and HPO 4-2 9. Which species would function as a buffer at physiological pH? a) H 2 PO 4- and PO 4-3 b) H 2 PO 4- and HPO 4-2 c) HPO 4-2 and PO 4-3 d) only PO 4-3 is involved, since it’s the best proton sponge e) only H 3 PO 4 is involved, since it’s the only species that donates a proton at this pH 10. The species present at point d is most accurately characterized as: (there is only one correct answer) a) a buffer system b) a strong acid c) a weak acid d) a weak base e) a strong base 14 — 13 — 12 — 11 — 10 — 9 — 8 — 7 — 6 — 5 — 4 — 3 — 2 — 1 — 0 l l l l l pH b c d Add H + Add OH- a 11. 11....
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This note was uploaded on 03/31/2008 for the course BIOCHEM 107 taught by Professor Toews during the Fall '07 term at UNC.

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107-2006_EXAM2-WEB - BIOCHEM 107 EXAM II(TOEWS& SANCAR...

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