# Problem: Calculate the pH of a solution that contains 1.0 M HF and 1.0 M HOC 6H5. Also calculate the concentration of OC6H5- in this solution at equilibrium.

###### FREE Expert Solution

$\overline{){{\mathbf{K}}}_{{\mathbf{a}}}{\mathbf{=}}\frac{\mathbf{products}}{\mathbf{reactants}}{\mathbf{=}}\frac{\left[{H}_{3}{O}^{+}\right]\left[{F}^{-}\right]}{\left[\mathrm{HF}\right]}}$

${\mathbf{6}}{\mathbf{.}}{\mathbf{76}}{\mathbf{×}}{{\mathbf{10}}}^{\mathbf{-}\mathbf{4}}{\mathbf{=}}\frac{\left(x\right)\left(x\right)}{1-x}\phantom{\rule{0ex}{0ex}}\phantom{\rule{0ex}{0ex}}{\mathbf{6}}{\mathbf{.}}{\mathbf{76}}{\mathbf{×}}{{\mathbf{10}}}^{\mathbf{-}\mathbf{4}}{\mathbf{=}}\frac{{x}^{2}}{1-x}$

Since Ka <<1, we can ignore x in the denominator.

${\mathbf{6}}{\mathbf{.}}{\mathbf{76}}{\mathbf{×}}{{\mathbf{10}}}^{\mathbf{-}\mathbf{4}}{\mathbf{=}}\frac{{x}^{2}}{1-\overline{)x}}\phantom{\rule{0ex}{0ex}}\phantom{\rule{0ex}{0ex}}{\mathbf{6}}{\mathbf{.}}{\mathbf{76}}{\mathbf{×}}{{\mathbf{10}}}^{\mathbf{-}\mathbf{4}}{\mathbf{=}}\frac{{\mathbf{x}}^{\mathbf{2}}}{\mathbf{1}}\phantom{\rule{0ex}{0ex}}\phantom{\rule{0ex}{0ex}}\sqrt{{\mathbf{x}}^{\mathbf{2}}}{\mathbf{=}}\sqrt{\mathbf{6}\mathbf{.}\mathbf{76}\mathbf{×}{\mathbf{10}}^{\mathbf{-}\mathbf{4}}}$

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###### Problem Details

Calculate the pH of a solution that contains 1.0 M HF and 1.0 M HOC 6H5. Also calculate the concentration of OC6H5- in this solution at equilibrium.