زیرا، داریم: $\left[ {{H}^{+}} \right]={{10}^{-4/4}}={{10}^{(0/3+0/3-5)}}={{10}^{0/3}}\times {{10}^{0/3}}\times {{10}^{-5}}=2\times 2\times {{10}^{-5}}=4\times {{10}^{-5}}$ $\alpha =\frac{\left[ {{H}^{+}} \right]}{\left[ HA \right]}\times 100=\frac{4\times {{10}^{-5}}mol{{L}^{-1}}}{0/0025mol{{L}^{-1}}}\times 100=%1/6$ $%1/6$