(17.2b.3)
A 8.57×10-2-M aqueous solution of CH3NH2 (methylamine) has a pH of 11.8. Calculate the pH of a buffer solution that is 8.57×10-2 M in CH3NH2 and 0.156 M in CH3NH3+.
pH = 11.8
pOH = 2.2
[OH-] = 6.309 x 10^-3 M
CH3NH2 + H2O --------------> CH3NH3+ + OH-
0.0857 0 0
0.0857-x x x
Kb = x^2 / 0.0857 - x
= (6.309 x 10^-3)^2 / 0.0857 - 6.309 x 10^-3
Kb = 5.014 x 10^-4
pKb = 3.30
pKa = 10.70
pH = pKa + log [base / acid]
= 10.70 + log [0.0857 / 0.156]
pH = 10.44
(17.2b.3) A 8.57×10-2-M aqueous solution of CH3NH2 (methylamine) has a pH of 11.8. Calculate the pH...
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