Quinine, C20H24N2O2, occurs naturally in the bark of the cinchona tree and was the first effective...

Quinine, C20H24N2O2, occurs naturally in the bark of the cinchona tree and was the first effective treatment for malaria. It is a diprotic base with Kb values of (the acidic protons are shown in red) C20H24N2O2 + H2O HC20H24N2O2+ + OH- Kb2 = 1.0 × 10-6 HC20H24N2O2+ + H2O H2C20H24N2O22+ + OH- Kb1 = 1.58 × 10-10

a) The recommended IV dose of quinine is 0.800 g/kg, that is, 0.800 g of quinine per 1 kg of water. If we assume that the density of the solution is 1.00 g/mL, what is the pH of this solution? The molar mass of quinine is 324.412 g/mol. For simplicity, abbreviate C20H24N2O2 as Q.

b) 100 mL of the solution from part a is then titrated with a solution of 0.010 M HCl. How many mL of HCl solution is required to reach the first equivalence point?

c) What is the pH at the first equivalence point?

d) What is the pH when 32.00 mL of HCl has been added?

e) What is the pH at the second equivalence point?

f) Quantitatively draw the resulting titration curve on the axes below. Be sure to label both axes, equivalence points and buffer regions. Be as accurate as use can and make use of your results for parts a-e. g) The pH in the stomach is often quite low, between 2 and 3. What species of quinine is predominant at a pH of 2.5?

h) The pH of blood is buffered at 7.4. What species of quinine is predominant at this pH?

Expert Solution

queen_honey_blossom answered 1 year ago

Quinine occurs naturally in the bark of the cinchona tree. For centuries, it was the only...

Quinine occurs naturally in the bark of the cinchona tree. For centuries, it was the only treatment for malaria. Quinine contains two weakly basic nitrogen atoms, with Kb1=3.31 x 10^-6 and Kb2=.00000000135 at 25 C. Calculate the pH of a .011 M solution of quinine in water.

Quinine is a natural product extracted from the bark of the cinchona tree, which is native...

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