Problem 3. Quinine is a bitter-tasting compound that is produced in the bark of

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Problem 3. Quinine is a bitter-tasting compound that is produced in the bark of the tropic cinchona tree and found n tonic water. Quinine also exhibits potent antimalarial properties. British colonists in India commonly drank tonic =CH water (mixed with gin) to avoid contracting Plasmodium falciparum, the malaria pathogen. Quinine also saved thousands of lives during the construction of the Panama canal. Quinine (CaoHoN O) contains two basic nitrogens. The amine nitrogen (shown in blue) is much more basic (pK, 5.1) than the aromatic nitrogen (pK, 9.7). a) A saturated solution of quinine in water is only 1.6x 10 M. What is the pH of the solution? b) Because of its low solubility, quinine is given as the salt quinine hydrochloride CaoHaaN O HO), which is 120 times more soluble than quinine. What is the pH of 0.33 M quinine hydrochloride? Problem 4 In your own words, explain entropy. Pretend you are explaining entropy to a relative who has not taken chemistry classes (a younger sibling or cousin, perhaps an aunt/uncle or grandparent). Give an example of an everyday process with AS >0 Problem 5 Determine if each of the following processes will be spontaneous or nonspontaneous. a) The earth moves around the sun. b) A boulder rolls up a hill. c) Average car prices increase d) Sodium metal and chlorine gas form solid sodium chloride at STP Problem 6. Predict which substance in each of the following pairs will have a greater molar entropy. Explain your answer NO2 or NaO a) c) HCI (g) or HBr (g

Explanation / Answer

3.

a. [quinine] = 1.6 x 10^-3 M

pKb1 = 5.1 = -log[Kb]

Kb = 7.9 x 10^-6

quinine + H2O <==> quininH+ + OH-

let x amount reacted

Kb = [quinineH+][OH-]/[quinine]

7.9 x 10^-6 = x^2/1.6 x 10^-3

x = [OH-] = 1.73 x 10^-4 M

pOH = -log[OH-] = 3.95

pH = 14 - 3.95 = 10.05

b) [quinineH+] = 0.33 M

pKa = 14 - 5.1 = 8.9

pKa = -log[Ka]

Ka = 1.26 x 10^-9

quinineH+ + H2O <==> quinine + H3O+

let x amount reacted

Ka = [quinine][H3O+]/[quinineH+]

1.26 x 10^-9 = x^2/0.33

x = [H3O+] = 2.04 x 10^-5 M

pH = -log[H3O+] = 4.70

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4. Entropy is degree of freedom or randomness. So if we go from solid (which is more rigid) to a liquid form (free flowing), we say entropy of the system has increases.

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5. processe

a) spontaenous

b) non-spontaneous

c) spontaneous

d) spontaneous

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6. molar entropy

a) NO2 as it has lesser moles than N2O4

b) CH3OCH3 as it cannot form hydrgen bond, entropy is higher.

c) HCl as mass of HCl is lower than HBr

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