We are asked to calculate the pH of a saturated aqueous solution of quinine.
Step 1. Calculate concentration
Molar mass = 324.4 g/mol
Molarity = 0.0016 M
Step 2. Set-up ICE chart
Step 3. Calculate [OH-]
Check if x in the denominator is negligible:
Since the ratio is < 500, x is not negligible.
Use quadratic formula:
From the equation, we have a = 1, b = 7.94×10–6, and c = 1.27 × 10–8. Solving for x
[OH-] = x = 1.09 x 10-4 M
Quinine (C20H24N2O2) is the most important alkaloid derived from cinchona bark. It is used as an antimalarial drug. For quinine, pK b1 = 5.1 and pK b2 = 9.7 (pK b = -log K b). Only 1 g quinine will dissolve in 1900.0 mL of solution. Calculate the pH of a saturated aqueous solution of quinine. Consider only the reaction Q + H2O ⇌ QH + + OH - described by pK b1, where Q = quinine.
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Our data indicates that this problem or a close variation was asked in Chemistry: An Atoms First Approach - Zumdahl Atoms 1st 2nd Edition. You can also practice Chemistry: An Atoms First Approach - Zumdahl Atoms 1st 2nd Edition practice problems.