Problem: In a 0.20 M solution, a weak acid is 3.0% dissociated.(a) Calculate the [H3O+], pH, [OH−], and pOH of the solution.

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FREE Expert Solution

Recall that the percent ionization is given by:

$\overline{){\mathbf{pH}}{\mathbf{=}}{\mathbf{-}}{\mathbf{log}}{\mathbf{\left[}}{{\mathbf{H}}}_{{\mathbf{3}}}{{\mathbf{O}}}^{{\mathbf{+}}}{\mathbf{\right]}}}$

$\overline{){\mathbf{pH}}{\mathbf{+}}{\mathbf{pOH}}{\mathbf{=}}{\mathbf{14}}}$

$\overline{)\left[{\mathrm{OH}}^{-}\right]{=}{{10}}^{-\mathrm{pOH}}}$

solve for [H3O+]:

$\mathbf{3}\mathbf{.}\mathbf{0}\mathbf{%}\mathbf{=}\frac{\mathbf{\left[}{\mathbf{H}}_{\mathbf{3}}{\mathbf{O}}^{\mathbf{+}}\mathbf{\right]}}{\mathbf{0}\mathbf{.}\mathbf{20}}\mathbf{×}\mathbf{100}$

$\mathbf{\left[}{\mathbf{H}}_{\mathbf{3}}{\mathbf{O}}^{\mathbf{+}}\mathbf{\right]}\mathbf{=}\mathbf{0}\mathbf{.}\mathbf{20}\mathbf{×}\frac{\mathbf{3}\mathbf{.}\mathbf{0}}{\mathbf{100}}$

[H3O+] = 0.006 M

Problem Details

In a 0.20 M solution, a weak acid is 3.0% dissociated.

(a) Calculate the [H3O+], pH, [OH], and pOH of the solution.