How could you prepare a buffer if only acetic acid, HCl and NaOH are available? If you must have a weak acid and a conjugate base for a buffer, if the conjugate base is not available, how could one generate it?
This makes no sense to me. Maybe I am overlooking something?
Take acetic acid and add NaOH to it. That produces sodium acetate, the base of the acid/base system. To make this work, one needs to use acetic acid and add NaOH but not enough to completely neutralize it.
For example, if you took 10 moles acetic acid and added 5 moles NaOH, that will give you 5 mol sodium acetate (the base) and will leave 5 moles acetic acid (the acid) and that gives you the acid/base pair you want. The HCl and NaOH, added drop wise to the completed solution is for final adjustment of the pH.
Makes sense. I guess I was over thinking it. Seemed too easy to be that. thank you for your time!
No, you are not overlooking anything. The question is indeed a bit confusing.
To prepare a buffer, you typically need a weak acid and its conjugate base. In this case, acetic acid (CH3COOH) is the weak acid. However, you mentioned that the conjugate base is not available.
In order to generate the conjugate base for the acetic acid, you can add sodium hydroxide (NaOH) to the solution. NaOH is a strong base and can react with acetic acid to form sodium acetate (CH3COONa), which is the conjugate base of acetic acid.
Here is the step-by-step process to prepare the buffer:
1. Start with acetic acid (CH3COOH) in a suitable container.
2. Add a calculated amount of sodium hydroxide (NaOH) to the acetic acid. The amount of NaOH required should be stoichiometrically equivalent to the amount of acetic acid present. This will ensure complete reaction and conversion of acetic acid to sodium acetate.
3. Stir the mixture well to ensure uniformity and complete reaction.
4. Once the reaction is complete, you will have a solution containing sodium acetate (CH3COONa), which is the conjugate base, along with water.
Now, you have a buffer solution consisting of acetic acid (weak acid) and sodium acetate (conjugate base). This combination will resist changes in pH when small amounts of acid or base are added.
It's important to note that while this method can provide a buffer solution, it's not an ideal approach since the strong base, NaOH, is used to generate the conjugate base. Ideally, you would prefer to have a weak acid and its corresponding conjugate base ready-made.