n the laboratory, a general chemistry student measured the pH of a 0.342 M aqueous solution of ethylamine, C2H5NH2 to be 12.067. Use the information she obtained to determine the Kb for this base.

Respuesta :

Answer:

The value of [tex]K_b[/tex] of the an ethylamine is [tex]4.121\times 10^{-4}[/tex].

Explanation:

The pH of the solution = 12.067

The pOH of the solution = 14 - pH =14-12.607 =1.933

[tex]pOH=-\log[OH^-][/tex]

[tex]1.933=-\log[OH^-][/tex]

[tex][OH^-]=0.0117 M[/tex]

[tex]C_2H_5NH_2+H_2O\rightleftharpoons C_2H_5NH_3^{+}+OH^-[/tex]

Initially

0.342 M                              0     0

At equilibrium

(0.342-x)                             x      x

The value of x = [tex][OH^-]=0.0117 M[/tex]

The expression of [tex]K_b[/tex]is given as:

[tex]K_b=\frac{[C_2H_5NH_3^{+}][OH^-]}{[C_2H_5NH_2]}[/tex]

[tex]K_b=\frac{x^2}{(0.342-x)}[/tex]

[tex]K_b=\frac{(0.0117 )^2}{(0.342-0.0117)}=4.121\times 10^{-4}[/tex]

The value of [tex]K_b[/tex] of the an ethylamine is [tex]4.121\times 10^{-4}[/tex].