help please Asap Nicotinic acid (niacin) is a monoprotic acid with the formula H
ID: 902637 • Letter: H
Question
help please Asap Nicotinic acid (niacin) is a monoprotic acid with the formula HC6H4NO2. A solution that is 0.012M in nicotinic acid has a pH of 3.39 at 25 degree C. What is the acid dissociation constant for this acid at 25 degree C? What is the pH at 25 degree C of the solution obtained by dissolving a 0.325g of acetylsalicylic acid, HC9H7O4 in 0.500L of water? The acid is monoprotic, and Ka equals 3.3 times 10^4 at 25 degree C. Morphine, C17H19NO3, is administered medically to relieve pain. It is a naturally occurring base, or alkaloid. What is the pH of a 0.0075 M solution of morphine at 25 degree C? The base dissociation constant is 1.6 times 10 6 at 25 degree C. A solution is prepared to be 0.10M acetic acid, HC2H3O2, and 0.20M sodium acetate, NaC2H3O2. What is the pH of this solution at 25 degree C? K0 for acetic acid at 25 degree C. is 1.8 times 10^-5.Explanation / Answer
(1) C = 0.012 M
pH = 3.39
[H+] = 10^-3.39 = 4.07 x 10^-4 M
Ka = [H+]^2 / C = (4.07 x 10^-4)^2 / 0.012
Ka = 1.38 x 10^-5
(2)
Ka = 3.3 x 10^-4
Concentration = C = (mass / molar mass ) x 1/ V
= (0.325 / 180) x 1/0.5
= 3.6 x 10^-3 M
[H+] = sqrt (Ka x C) = sqrt (3.3 x 10^-4 x 3.6 x 10^-3)
[H+] = 1.089 x 10^-3
pH = -log[H+] = -log(1.089 x 10^-3 )
pH = 2.96
(3)
[OH-] = sqrt (Kb x C ) = sqrt (1.6 x 10^-6 x 0.075) = 1.095 x 10^-4M
pOH = -log[OH-] = -log ( 1.095 x 10^-4) = 3.96
pH + pOH =14
pH = 10.04
(4)
Ka = 1.8 x 10^-5
pKa = -log Ka = -log (1.8 x10^-5) = 4.74
pH = pKa + log [sodium acetate / aceic acid]
pH = 4.74 + log (0.2 / 0.1)
pH = 5.04
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