This thing has been bugging me for a few days. I don't understand why a strong acid displaces a weak acid from it's salt solution.

  • 3
    $\begingroup$ And what do you mean by "displacing"? What would happen according to you if some HCl was added to solution of sodium acetate (for example)? $\endgroup$
    – Mithoron
    May 5, 2020 at 15:29

1 Answer 1


Maybe you prefer an image. Bases behave with $\ce{H+}$ like magnets with nails. Suppose a $\ce{H+}$ ion (a proton) is like a piece of iron (nail) attracted by a weak magnet. It forms a couple which may more or less look like an acid molecule. If now a big and strong magnet (a strong base) approaches, it will pick up the nail, and the weak magnet will stay alone. If the nail is fixed on a small magnet it makes a weak acid. And if you approach a strong magnet (a strong base like OH-), the proton will leave the weak base, and be fixed against the strong base. For example, if the weak base is the ion acetate, the initial couple weak base + proton is the acetic acid. If a strong base like OH- approaches, there will be a proton transfer, from the weak base to the strong base $\ce{OH^-}$. Water will be produced, leaving the weak base (acetate) alone. The proton transfer is like a nail transfer between magnets. Strong bases are like strong magnets. Strong acid is a strong donor. So the corresponding magnet is extremely small and weak. A tiny magnet + nail is able to donate its nail to any other base. A strong acid is able to donate its proton to any medium or strong base.


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