Problem 16.73 Ephedrine, a central nervous system stimulant, is used in nasal sp
ID: 939507 • Letter: P
Question
Problem 16.73
Ephedrine, a central nervous system stimulant, is used in nasal sprays as a decongestant. This compound is a weak organic base:
C10H15ON(aq)+H2O(l)C10H15ONH+(aq)+OH(aq)
A 0.035 M solution of ephedrine has a pH of 11.33.
Part A
What is the equilibrium concentration of C10H15ON?
Express your answer using two significant figures.
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Part B
What is the equilibrium concentration of C10H15ONH+?
Express your answer using two significant figures.
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Part C
What is the equilibrium concentration of OH?
Express your answer using two significant figures.
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Part D
Calculate Kb for ephedrine.
Express your answer using two significant figures.
[C10H15ON] = MExplanation / Answer
Answer – Given, [C10H15ON] = 0.035 M , pH = 11.33
We know,
pH + pOH = 14
so, pOH = 14- pH
= 14- 11.33
= 2.67
So, [OH-] = 10-pOH
= 10-2.67
= 0.00214 M
We know
C10H15ON + H2O ------> C10H15ONH+ + OH-
I 0.035 0 0
C -x +x +x
E 0.035-x +x +x
We know, at equilibrium, [OH-] = x = 0.00214 M
Part A) [C10H15ON] = 0.035 -x
= 0.035-0.00214
= 0.033 M
Part B)
We know, [C10H15ONH+] = x = 0.0021 M
Part C) , [OH-] = x = 0.0021 M
Part D)
Kb = [C10H15ONH+][OH-] / [C10H15ON]
= 0.00214 *0.00214 / 0.033
= 1.4* 10-4