Respuesta :
Explanation:
Let the reaction equation for the dissociation of weak acid is as follows.
[tex]HA \rightarrow H^{+} + A^{-}[/tex]
Initial: 0.87 0 0
Change: -x +x +x
Equilibrium: 0.87 - x +x +x
Hence, expression for the dissociation constant will be as follows.
[tex]k_{a} = \frac{[H^{+}][A^{-}]}{[HA]}[/tex]
Now, putting the given values into the above formula as follows.
[tex]k_{a} = \frac{[H^{+}][A^{-}]}{[HA]}[/tex]
[tex]4.3 \times 10^{-7} = \frac{x \times x}{(0.187 - x)}[/tex]
x = 0.000283
Hence, at equilibrium the concentration of hydrogen ions is 0.000283.
or, [tex][H^{+}] = 2.83 \times 10^{-4}[/tex]
[tex][H^{+}] = C \times \alpha[/tex]
Also, [tex]\alpha = \frac{[H^{+}]}{C}[/tex]
= [tex]\frac{0.000283}{0.187}[/tex]
= 0.00151
And, the percentage of dissociation is [tex]0.00151 \times 100[/tex] = 0.151%
Thus, we can conclude that percent dissociation of given weak acid is 0.151%.
