Question

If 15% of a O.1 M solution of a weak acid dissociates into H+ and A- ions, what is the concentration of H3O+? (HA + H2O --> H3O+ + A-) ?

Answer 1

Would it not be `0.015*mol*L^-1` with respect to `H_3O^+`?

Explanation:

And so we should address the equilibrium...

`HA(aq) +H_2O(l)rightleftharpoonsH_3O^+ + A^(-)`

Initially, `[HA]=0.1*mol*L^-1`...finally...`[H_3O^+]-=[A^-]-=0.015*mol*L^-1`...and `[HA]-=0.1-0.015,` and we could work out `K_a` from these data...

`K_a=([H_3O^+][A^-])/([HA])=(0.015xx0.015)/(0.1-0.015)=2.65xx10^-3`...