The Kb of dimethylamine [(CH3)2NH] is 5.90×10-4 at 25°C. Calculate the pH of a 1.80×10-3 M...

The Kb of dimethylamine [(CH3)2NH] is 5.90×10-4 at 25°C. Calculate the pH of a 1.80×10-3 M solution of dimethylamine.

Expert Solution

The ionization of dimethyl amine is

(CH3)2NH + H2O <=> (CH3)2NH2+ + OH-

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

ICE table is prepared

compound initial change equilibrium

(CH3)2NH 1.8*10^-3 -x 1.8*10^-3-x

(CH3)NH2+ 0 x x

OH- 0 x x

Kb= x²/(1.8*10^-3-x)= 5.9*10^-4 , when solved using excel, x= 7.78*10^-4, [OH-]= 7.78*10^-4, pOH= 3.1, pH= 14-3.1=10.9

queen_honey_blossom answered 2 years ago

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