A certain weak acid, HA, has a Ka value of 1.8×10−7. Calculate the percent ionization of HA in a 0.10 M solution. Express your answer to two significant figures and include the appropriate units.

Respuesta :

Answer: The percent ionization of HA is 0.13 %

Explanation:

We are given:

Molarity of HA solution = 0.10 M

The chemical equation for the ionization of HA follows:

                     [tex]HA\rightarrow H^++A^-[/tex]

Initial:            0.1

At eqllm:      (0.1-x)   x    x

The expression of [tex]K_a[/tex] for above equation follows:

[tex]K_a=\frac{[H^+][A^-]}{[HA]}[/tex]

We are given:

[tex]K_a=1.8\times 10^{-7}[/tex]

Putting values in above equation, we get:

[tex]1.8\times 10^{-7}=\frac{x\times x}{0.1-x}\\\\x^2+(1.8\times 10^{-7})x-1.8\times 10^{-8}=0\\\\x=0.00013,-0.00013[/tex]

Neglecting the negative value of 'x' because concentration cannot be negative.

To calculate the percent ionization, we use the equation:

[tex]\%\text{ ionization}=\frac{[H^+]_{eq}}{[HA]_i}\times 100[/tex]

[tex][H^+]_{eq}=x=0.00013M[/tex]

[tex][HA]_i=0.1M[/tex]

Putting values in above equation, we get:

[tex]\%\text{ ionization}=\frac{0.00013}{0.1}\times 100\\\\\%\text{ ionization}=0.13\%[/tex]

Hence, the percent ionization of HA is 0.13 %