A weak acid $\mathrm{H} A$ has degree of dissociation $x$. Which option gives the correct expression

Question

A weak acid $\mathrm{H} A$ has degree of dissociation $x$. Which option gives the correct expression of $\left(\mathrm{pH}-\mathrm{p} K_{a}ight)$ ?\

Professor PC Thomas Classes · Answer

(c)  Taking $\log$ on both sides (with negative sign), we get\ $-\log \left(K_{a}ight)=-\log (a x)-\log \left(\frac{x}{1-x}ight)$\ $\mathrm{p} K_{a}=\mathrm{pH}-\log \left(\frac{x}{1-x}ight)$ (As $\left.\mathrm{H}^{+}=a xight)$\ $\mathrm{pH}-\mathrm{p} K_{a}=\log \left(\frac{x}{1-x}ight)$