2010 Test 2 - Solutions

2010 Test 2 - Solutions - You are writing VERSION 1 of this...

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1 Last Page You are writing VERSION 1 of this test. Make sure you have correctly entered your version number (“1”) in the correct column on your scan sheet (see p. 2 for details). ____ 1. An student thinks they have prepared a pure sample of Aspirin. Which of the following observations provides evidence their sample is not pure. a. Upon reaction with concentrated H 2 SO 4 , the aroma of acetic acid was present. b. In the thin layer chromatography, two spots appeared from the sample. c. The melting point of the sample was sharp at 135°C. d. The sample was white. e. The calculated percent yield was 84%. ____ 2. Which of the following statements is incorrect with regards to a titration of a weak base with a strong acid? a. At the equivalence point, moles of acid added will be equal to the initial moles of base b. At the equivalence point, the resulting solution is acidic c. The titration becomes buffered at some point between the start of the titration and the equivalence point. d. After the equivalence point, the pH of the solution will continue to decrease. e. At the half equivalence point, pH = p K b of the weak base Section #1 – These questions are worth two marks each. At ½ equivalence point, the pH is the pK a of the conjugate acid.
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2 Last Page ____ 3. An alternative explanation for HVA activity is that it stimulates dopamine- consuming cells rather than suppressing dopamine-producing cells. If that were true, what would be the best high throughput assay for HVA activity? a. grow dopamine-producing cells, assay for lower [dopamine] in the presence of HVA b. grow dopamine-consuming cells, assay for lower [dopamine] in the presence of HVA c. grow dopamine-consuming cells, add dopamine, assay for higher [dopamine] in the presence of HVA d. grow dopamine-producing cells, add dopamine, assay for lower [dopamine] in the presence of HVA e. grow dopamine-consuming cells, add dopamine, assay for lower [dopamine] in the presence of HVA ____ 4. Assume that HVA interfered with the high throughput assay for dopamine, preventing dopamine from being detected even when it was present. Which results in the control experiments would be observed? Need to look for a control test where there is HVA and dopamine present, but no dopamine is showing up on the test. The last column (4) is the one that helps determine the correct answer.
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3 Last Page ____ 5. Assuming that the compound below is aromatic, how many lone pairs of electrons are not part of the delocalized pi-electron system? a. 4 b. 5 c. 2 d. 3 e. 1 ____ 6. Which of the following compounds are aromatic? (You may assume that all compounds are planar if they meet all the other criteria for aromaticity.) a. ii, iv b. i, iii, iv c. i, iii d. i, ii, iv e. ii, iv, v The oxygen will donate one pair of electrons to the delocalized system, the other pair will be in the hybridized sp 2 orbital. The nitrogen that has a double bond will contribute one electron to the pi-system (creating the double bond) and the lone pair will be in
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2010 Test 2 - Solutions - You are writing VERSION 1 of this...

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