[Calgary Pure]

Hi,

From what I've learned so far, strong acids are those that react completely with water, and weak acids and those that do not. If this is the case, then if you were to put a weak acid in water, there wouldn't be as many hydronium ions as there are hydrogen atoms in the acid.

However, when our teacher showed the neutralization reaction between a weak acid and a strong base, she assumed that all of the hydrogen atoms in the acid ionized.

eg. H3PO4 + 3NaOH ---> 3H2O + Na3PO4 And she would say that if we had 1 mole of phosphoric acid (excess sodium hydroxide), we would get 3 moles of water.

I always thought that for a reaction to take place, the compounds would have to ionize/dissociate first, and since the weak acid doesn't ionize completely, not all of it would be able to react. So having 1 mole of phosphoric acid wouldn't really yield 3 moles of hydrogen ions, and 3 moles of water wouldn't be produced.

This really confuses me. I would really appreciate it if someone can help me understand whether I'm mistaken, or if the teacher is doing this for simplification.

Thank you in advanced.

[Arkcon]

When a weak acid partially ionizes, it exits in equilibrium with its non-ionized form.  When you mix it with strong base, you will consume all of the ionized form.  Can you guess what happens next?

[Borek]

I would really appreciate it if someone can help me understand whether I'm mistaken, or if the teacher is doing this for simplification.

Both. Arkcon already pointed you in the right direction to show what you were missing, and the example your teacher used is not the best one, as you need a really large excess of a strong base to completely neutralize phosphoric acid.

[Calgary Pure]

Alright thank you very much, makes a lot more sense now.