Morphine, C17H19NO3, is administered medically to relieve pain. It is a naturally occurring base, or alkaloid. What is the pH of a 0.0025 M solution of morphine at 25°C? The base-ionization constant,

Question

Morphine, C17H19NO3, is administered medically to relieve pain. It is a naturally occurring base, or alkaloid. What is the pH of a 0.0025 M solution of morphine at 25°C? The base-ionization constant, Kb, is 1.6 × 10^-6 at 25°C. (log 2 = 0.3)

Prashant Kotian · Accepted Answer

Correct answer: B. For the weak base morphine (B): [OH-] = sqrt(Kb × C) = sqrt(1.6 × 10^-6 × 0.0025) = sqrt(4.0 × 10^-9) = 6.32 × 10^-5 M. pOH = -log[OH-] = -log(6.32 × 10^-5) = 5 - log 6.32 = 5 - 0.8 = 4.2. pH = 14 - pOH = 14 - 4.2 = 9.8.

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