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It has been found that the `pH` of a `0.01 M` solution of an orginic acid is `4.15`. Calculate the concentration of the anion, the ionization constant of the acid and its `pK_(a)`. |
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Answer» `HA hArr H^(o+)+A^(Θ)` `pH=-log [H^(o+)]` or `log [H^(o+)]=- pH=-4.15=bar(5).85` `:. [H^(o+)]=7.09xx10^(-5)M=7.08xx10^(-5)M` `[A^(Θ)]=[H^(o+)]=7.08xx10^(-5)M` `K_(a)=([H^(o+)][A^(Θ)])/([HA])=((7.08xx10^(-5))(7.08xx10^(-5)))/10^(-2)` `=5.08xx10^(-7)` `pK_(a)=-log K_(a) =-log(5.0xx10^(-7))=7-0.699=6.301` Alternatively `pH_(W_(A))=1/2(pK_(a)-log C)` `4.15xx2=pK_(a)-log 10^(-2)` `8.30-2=pK_(a)` `pK_(a)=6.30` |
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