Codeine (c18h21no3) is a weak organic base. a 5.0 x 10-3 m solution of codeine has a ph of 9.95. what is the pkb for this base

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Chemistry

Sawyer Blackwell

5 February, 14:45

Codeine (c18h21no3) is a weak organic base. a 5.0 x 10-3 m solution of codeine has a ph of 9.95. what is the pkb for this base

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Answers (1)

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Derrick Galvan · Answer 1

Answer is: pKb for codeine is 5,8.

Chemical reaction: C₁₈H₂₁NO₃ + H₂O ⇄ C₁₈H₂₁NO₃H⁺ + OH⁻.

c (C₁₈H₂₁NO₃) = 5·10⁻³ M = 0,005 mol/L.

pH = 9,95.

pOH = 14 - 9,95 = 4,05.

[OH⁻] = 10∧ (-4,05) = 0,000089 mol/L.

[OH⁻] = [C₁₈H₂₁NO₃H⁺] = 8,9·10⁻⁵ mol/L.

[C₁₈H₂₁NO₃] = 0,005 mol/L - 0,000089 mol/L = 0,004911 mol/L.

Kb = [OH⁻] · [C₁₈H₂₁NO₃H⁺] / [C₁₈H₂₁NO₃].

Kb = (0,000089 mol/L) ² / 0,004911 mol/L = 1,613·10⁻⁶.

pKb = - log (1,613·10⁻⁶) = 5,8.