why is a weak acid weak base titration different from strong acid strong base/ weak acid strong base/strong acid weak base?
Any combination of acid and base titration will give a SHARP end point caused by a large increase (or decrease depending upon what is titrating what) of about 4 or 5 pH units EXCEPT for the titration of a weak acid with a weak base. With the WA/WB titration it is essentially impossible to determine where the inflection point(the equivalence point) is located. Color indicator rely on a color change over a pH range of two (2) pH units and that occurs with just a drop of titrant. With a WA/WB titration, one drop causes no such color change because the increase in pH is not noticeably different. Look in your text for the titration curves and you can see what I'm talking about. Or go to google and type in pictures of titration curves. Perhaps I can find one on the web if yu can't find one. We can't draw them on this board.
so then for a weak acid weak base titration indicators don't work?
That's right. They (color indicators) don't work for WA/WB titrations.
A weak acid-strong base titration is different from other types of acid-base titrations because it involves the reaction between a weak acid and a strong base.
In a weak acid-strong base titration, the weak acid does not dissociate completely in water, meaning that only a fraction of the acid molecules will release their hydrogen ions (H+). As a result, the concentration of H+ ions in the solution is relatively low.
On the other hand, a strong base solution contains a high concentration of hydroxide ions (OH-). When the strong base is added to the weak acid solution, the hydroxide ions react with the partially dissociated acid molecules. This reaction leads to the neutralization of the weak acid and the formation of water and a weakly basic salt.
The key difference between a weak acid-strong base titration and other types of titrations lies in the pH curve. In a weak acid-strong base titration, the pH curve will be relatively flat around the equivalence point because the weak acid does not completely dissociate. This means that even after adding a stoichiometrically equivalent amount of strong base, the pH of the solution will not increase sharply like it does in other titrations.
To perform a titration between a weak acid and a strong base, you would need the following:
1. A burette to add the strong base solution incrementally to the weak acid solution. Ensure that you accurately measure the volume of the base solution added.
2. A pH meter or indicator to monitor the pH of the solution during the titration. This will help determine the equivalence point, where the weak acid is completely neutralized.
3. The weak acid solution, which should be accurately measured.
4. The strong base solution, typically sodium hydroxide (NaOH), which should also be accurately measured.
To perform the titration:
1. Add a known volume of the weak acid solution into a flask.
2. Using the burette, slowly add the strong base solution to the flask while continuously swirling the flask to ensure thorough mixing.
3. Monitor the pH of the solution using a pH meter or indicator. The pH will increase gradually as the strong base reacts with the weak acid.
4. Note any significant changes in the pH curve. The equivalence point will be where the pH remains relatively constant.
5. Calculate the amount of strong base required for neutralization using the balanced chemical equation for the reaction between the weak acid and strong base.
Understanding the concept and procedure behind specific acid-base titrations will help you differentiate between different types of titrations and their outcomes.