Question

papl 16. Phosphatidylcholine lipids are very common in eukaryotic cell membranes. Their structure resemble trimethylamine, (CH3)3N. What is the pOH of a 0.085 M solution of trimethylamine if th Kb 6.46 x 10 at 25°C? A. 4.19 B. 11.56 C. 2.63 D. 3.48 E. 9.38

Answer 1

Answer:

The reaction for the trimethylamine

TMA + H₂O --> TMAH⁺ + OH^-

	TMA + H2O (excess) -->	TMAH+   +	OH-
Initial	0.085	0	0
Change	-a	+a	+a
Equilibrium	0.085 - a	a	a

K_b = [a][a]/[0.085 - a] = 6.46 x 10^-5

a² + 6.46 x 10^-5 a - 5.491 x 10^-6 = 0

or a ~~ 0.002321 = [OH^-]

and pOH = -log(0.002321) = 2.63 option C

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