If the dissociation constant of HCN is 10^{-7 | vedclass

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(D) $KCN$ is a salt of a weak acid $(HCN)$ and a strong base $(KOH)$.For such a salt,the $pH$ is given by: $pH = 7 + \frac{1}{2}pK_a + \frac{1}{2}\log

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$9, 10^{-2}, 10^{-5}$

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(D) $KCN$ is a salt of a weak acid $(HCN)$ and a strong base $(KOH)$.For such a salt,the $pH$ is given by: $pH = 7 + \frac{1}{2}pK_a + \frac{1}{2}\log C$.Given $K_a = 10^{-7}$,so $pK_a = 7$. $C = 10^{-3} \ M$.$pH = 7 + \frac{1}{2}(7) + \frac{1}{2}\log(10^{-3}) = 7 + 3.5 - 1.5 = 9$.Degree of hydrolysis $(h)$ is given by: $h = \sqrt{\frac{K_w}{K_a 	imes C}} = \sqrt{\frac{10^{-14}}{10^{-7} 	imes 10^{-3}}} = \sqrt{10^{-4}} = 10^{-2}$.Concentration of $[OH^-]$ is given by: $[OH^-] = C 	imes h = 10^{-3} 	imes 10^{-2} = 10^{-5} \ M$.

If the dissociation constant of $HCN$ is $10^{-7}$,what are the values of $pH$,$h$ (degree of hydrolysis),and $[OH^-]$ for a $10^{-3} \ M$ solution of $KCN$,respectively?

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