Question

Calculate the molar concentration of OH^{-} ions in a
8.1 x 10^{-2} M solution of ethylamine (K_{b}= 6.4
x 10^{-4}).

Calculate the pH of this solution.

Answer #1

Molarity . . . . . .C2H5NH2 + H2O <==> C2H5NH3+ +
OH-

Initial . . . . . . . . . .0.81 . . . . . . . . . . . . . . .0 . .
. . . .0

Change . . . . . . . . . .-x . . . . . . . . . . . . . . . .x . . .
. . .x

At Equil. . . . . . 0.81 - x . . . . . . . . . . . . . . .x . . . .
. .x

pH = 11.87

pOH = 14.00 - pH = 14.00 - 11.87 = 2.13

[OH-] = 10^-pOH = 10^-2.13 = 0.0074 = x

Kb = [C2H5NH3+][OH-] / [C2H5NH2] = x^2 / (0.81 - x) = 6.4 x
10^-4

x^2 = 5.184 x 10^-4 - 6.4 x 10^-4 * x

x = 0.0224

so [OH-] = 0.0224 mol/L or (M)

pOH = -log( [OH-]) = 1.65

pH = 14 - pOH = 14 - 1.65 = 12.35 Answer

A)Calculate the molar concentration of OH− ions in a 0.540
M solution of hypobromite ion (BrO−; Kb=4.0×10−6)
.
B)What is the pH of this solution?

Find the [OH−] in a 0.340 M solution of ethylamine (C2H5NH2).
For ethylamine, Kb=5.6⋅10−4.

1(A)What is the pH of a 0.448 M solution of HF with ka =
6.8*10-4?
(B)In part A you probably made the approximation that 0.448 - x
0.448. Check the approximation by calculating the % that x is of
0.448.
2)a)Calculate the molar concentration of OH− ions in an 1.71 M
solution of hypobromite ion (BrO−; Kb = 4.0 10-6).
b)What is the pH of this solution?

Calculate the pH of a 0.0416 M aqueous solution of ethylamine
(C2H5NH2, Kb = 4.3×10-4) and the equilibrium concentrations of the
weak base and its conjugate acid.
pH
=
[C2H5NH2]equilibrium
=
M
[C2H5NH3+
]equilibrium
=

Calculate the pH of a solution that has a hydroxide ion
concentration [OH-], 5.03 x 10^-9 M?

Find [OH-] concentration of a 4.25x10^-4 M solution of
HOCH2CH2NH2, kb = 3.1 x 10^-5.
My x value is coming out to 2.35..? Ans: 1.0 x 10^-4

1). Calculate the pH and the concentration [Na+] =of all species
in 3.5×10−2 molar sodium cyanide solution. [Na+] = ___ M H+] = ___M
pH = ___M [OH−] =___M [CN−] = ___M [HCN]= ___M

Calculate the molar solubility of Fe(OH)2 in a buffer
solution where the pH has been fixed at the indicated values.
Ksp = 7.9 x 10-16.
(a) pH 7.7
M
(b) pH 11.0
M
(c) pH 13.7
M

Calculate the molar solubility of Fe(OH)2 in a buffer
solution where the pH has been fixed at the indicated values.
Ksp = 7.9 x 10-16.
(a) pH 8.2
M
(b) pH 10.8
M
(c) pH 12.3
M

the pH of .10 M ethylamine is 11.82
a) Calculate the Kb for ethyamine using the information
provided
b) based on your answer in (a) calculate the pH of .15
ethylammonium chloride

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