Consider a 0.64 M solution of dimethylamine, (CH3)2NH (Kb = 5.4×10-4). Mark the major species in...

Consider a 0.64 M solution of dimethylamine, (CH₃)₂NH (K_b = 5.4×10^-4).

Mark the major species in the solution.

_______TrueFalse (CH₃)₂NH
_______TrueFalse (CH₃)₂NH₂⁺
_______TrueFalse H₂O
_______TrueFalse H⁺
_______TrueFalse OH^-

Complete the following table (in terms of "x", the amount of dimethylamine which reacts). Minus signs must be included, omit positive signs and omit molarity units (they are assumed).

	(CH₃)₂NH	(CH₃)₂NH₂⁺	OH^-
Initial
Change
Equilibrium	0.64 - x

Determine the equilibrium concentration of (CH₃)₂NH₂⁺
M

Calculate the pH of the solution.
pH =

Solutions

Expert Solution

(CH3)2NH ----------------> (CH3)2NH2+ + OH-

0.64 0 0 ---------> initial

- x +x +x ---------> change

0.64 - x x x ---------> equilibrium

Kb = [(CH3)2NH2+][OH-] / [(CH32NH)]

5.4 x 10^-4 = x^2 / 0.64 - x

x = 0.0183

equilibrium concentration of (CH3)2NH2+ = 0.018 M

[OH-] = 0.0183 M

pOH = - log (0.0183) = 1.74

pH = 12.26

Major species :

OH- , (CH3)2NH2+ , (CH3)2NH

queen_honey_blossom answered 1 year ago

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