Question

Find pH if $\mathbf{pKa}\mathbf{=}\mathbf{3}\mathbf{.}\mathbf{00}$instead of $\mathbf{2}\mathbf{.}\mathbf{00}$Does the answer make sense?

Short answer

The $\mathrm{pH}\mathrm{if}\mathrm{pKa}=3.00$then $3.07$

Step-by-step solution

Define the acid dissociation constant

The acid dissociation constant ${\mathrm{K}}_3$can be given as,localid="1654854432154" ${\mathrm{K}}_3=\frac{\left[{\mathrm{H}}^{-}\right]\left|{\mathrm{A}}^{-}\right|}{\left[HA\right]}$

A weak acid is one that doesn't undergo completion

Step 2: Calculate the H+ ion for Ka.

The ${\mathrm{H}}^{+}$can be calculated from

$$\begin{gathered} \mathrm{HA}◽{\mathrm{H}}^{+}+{\mathrm{A}}^{-}{\mathrm{nK}}_{\mathrm{a}} \\ {\mathrm{K}}_{\mathrm{a}}=\frac{\left[{\mathrm{H}}^{+}\right]{\mathrm{IA}}^{-}]}{\left[\mathrm{HA}\right]} \\ {10}^{-3.00}=\frac{\left(\mathrm{X}\right)\left(0.0100+\mathrm{X}\right)}{\left(0.0100-\mathrm{X}\right)} \\ \mathrm{X}=8.44\times {10}^{-4} \\ \mathrm{Now}\mathrm{Ph}. \\ \mathrm{pH}=-\log \left(8.44\times {10}^{-4}\right) \\ \mathrm{pH}=3.07 \end{gathered}$$

Thus, The $\mathrm{pH}\mathrm{if}{\mathrm{pK}}_3=3.00$then$3.07$