The pH of a $0.01$ M weak acid $\mathrm{HX}\left({\mathrm{K}}_{\mathrm{a}}=4\times {10}^{-10}\right)$ is found to be 5 . Now the acid solution is diluted with excess of water so that the pH of the solution changes to $6$ . The new concentration of the diluted weak acid is given as $x\times {10}^{-4}\mathrm{M}$. The value of x is ______ (nearest integer)

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YESPYQ · Accepted Answer

Correct answer: b) 25. $pH=6\ [{H}^{+}]={10}^{−6}$ $[{H}^{+}]={10}^{−6}=\sqrt{{K}_{a}C}$ ${10}^{−6}=\sqrt{4\times {10}^{−10}\times C}$ $\frac{{10}^{−12}}{4\times {10}^{−10}}=C$ $0.25\times {10}^{−2}=C$ $25\times {10}^{−4}=C\ ∴x=25$

The pH of a \(0.01\) M weak acid \(\mathrm{HX}\left({\mathrm{K}}_{\mathrm{a}}=4\times {10}^{-10}\right)\) is found to be…

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