The pH of 0.1 M monobasic acid is 4.50. Calculate the concentration of the species H^(+), A^(-) and HA at equilibrium. Also determine the value of K_(a) and pK_(a) of the monobasic acid.

The pH of 0.1 M monobasic acid is 4.50. Calculate the concentration of

1.	The pH of 0.1 M monobasic acid is 4.50. Calculate the concentration of the species H^(+), A^(-) and HA at equilibrium. Also determine the value of K_(a) and pK_(a) of the monobasic acid.
Answer» SOLUTION :`HA hArr H^(+)+A^(-),log [H^(+)] = - PH = - 4.50 = bar(5).5` `:. [H^(+)]=3.16xx10^(-5)M` `[H^(+)]=[A^(-)]=3.16xx10^(-5)M` `[HA]=(0.1-3.16xx10^(-5))~= 0.1M` `K_(a) = (3.16xx10^(-5))^(2//0.1)=1.0 xx 10^(-8), pK_(a)=8`.