16. a.) In the laboratory, a general chemistry student measured the pH of a 0.37

Question

16.

a.)In the laboratory, a general chemistry student measured the pH of a 0.376 M aqueous solution of caffeine, C8H10N4O2to be 12.108.

Use the information she obtained to determine the Kb for this base.

Kb(experiment) = _____________

b.)In the laboratory, a general chemistry student measured the pH of a 0.376 M aqueous solution of morphine, C17H19O3N to be 10.738.

Use the information she obtained to determine the Kb for this base.

Kb(experiment) =

c.)
In the laboratory, a general chemistry student measured the pH of a 0.376 M aqueous solution of triethanolamine, C6H15O3N to be 10.653.

Use the information she obtained to determine the Kb for this base.

Kb(experiment) =

Explanation / Answer

a.)

pH = 12.108

pOH = 1.892

[OH-] = 0.0128 M

concentration C = 0.376 M

[OH-] = sqrt (Kb x C)

0.0128^2 = Kb x 0.376

Kb = 4.37 x 10^-4

b.)

pH = 10.738

pOH = 3.262

[OH-] = 5.47 x 10^-4 M

concentration C = 0.376 M

[OH-] = sqrt (Kb x C)

5.47 x 10^-4 = sqrt (Kb x 0.376)

Kb = 7.96 x 10^-7

c.)

pH = 10.653

pOH = 3.347

[OH-] = 4.50 x 10^-4 M

concentration C = 0.376 M

[OH-] = sqrt (Kb x C)

4.50 x 10^-4 = sqrt (Kb x 0.376)

Kb = 5.38x 10^-7

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