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6-2.Equilibrium-II (Ionic Equilibrium)
medium
$10^{-3}\, M \,HCN$ દ્રાવણ માટે એ $10\%$ તો દ્રાવણની $K_a$ અને $pH$ શોધો.
A
$10^{-3},9$
B
$10^{-4},6$
C
$10^{-5},4$
D
$10^{-6},7$
Solution
${\text{(i) }}{{\text{K}}_{\text{a}}} = C{\alpha ^2} = {10^{ – 3}} \times \frac{{10}}{{100}} \times \frac{{10}}{{100}} = \frac{1}{{100000}} = {10^{ – 5}}$
$(ii)\,{\text{pH}} = \frac{{\text{1}}}{{\text{2}}}p{K_a} – \frac{1}{2}\log c\,\,\,\,\,\,\,\,\because \,\,{K_a} = {10^{ – 5}}$
$pH = \frac{1}{2} \times 5 – \frac{1}{2}\log \,{10^{ – 3}}\,\,\,\,\,\,\,\,\,\,\,\therefore \,p{K_a} = 5$
$ = \frac{5}{2} + \frac{3}{2} = \frac{8}{2} = 4$
Standard 11
Chemistry
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