What is the percent ionization of a 1.8 M HC2H3O2 solution (Ka = 1.8 10-5 ) at 25°C?
A) 0.57 %
B) 0.32 %
C) 2.2 %
D) 0.18 %
E) 0.24 %

Respuesta :

Answer:

B) 0.32 %

Explanation:

Given that:

[tex]K_{a}=1.8\times 10^{-5}[/tex]

Concentration = 1.8 M

Considering the ICE table for the dissociation of acid as:-

[tex]\begin{matrix}&CH_3COOH&\rightleftharpoons &CH_3COOH&+&H^+\\ At\ time, t = 0 &1.8&&0&&0\\At\ time, t=t_{eq}&-x&&+x&&+x\\ ----------------&-----&-&-----&-&-----\\Concentration\ at\ equilibrium:-&1.8-x&&x&&x\end{matrix}[/tex]

The expression for dissociation constant of acid is:

[tex]K_{a}=\frac {\left [ H^{+} \right ]\left [ {CH_3COO}^- \right ]}{[CH_3COOH]}[/tex]

[tex]1.8\times 10^{-5}=\frac{x^2}{1.8-x}[/tex]

[tex]1.8\left(1.8-x\right)=100000x^2[/tex]

Solving for x, we get:

x = 0.00568  M

Percentage ionization = [tex]\frac{0.00568}{1.8}\times 100=0.32 \%[/tex]

Option B is correct.

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