Which of the following Acid+Base titration combinations would have a buffering region in their plot?

1)Strong Acid+Strong base (HCl+NaOH)
2)Weak acid and strong base (Acetic+NaOH)
3)Strong Acid and weak base (HCl+NH3)
4)Weak Acid and weak base (Acetic+NH3)

In all cases, there is 8ml of .1M Acid, and the NaOH is .100 M as well.

And btw, bases are being titrated into acids.

It doesn't matter how what is titrated with what, B, C, and D will have a buffered region. Technically, and many students don't realize it, BUT a strong acid/strong base is also buffered at the beginning of the titration

To determine which acid-base titration combinations would have a buffering region in their plot, we need to consider the properties of the acids and bases involved.

In a titration, a buffer region is observed when a weak acid or base is titrated with a strong acid or base. This buffer region occurs when both the weak acid and its conjugate base (or weak base and its conjugate acid) are present in significant amounts.

Let's analyze the given combinations:

1) Strong Acid + Strong Base (HCl + NaOH):
In this combination, both HCl and NaOH are strong acids and bases, respectively. Strong acids and bases do not form buffers because they dissociate completely, leaving no significant concentration of the weak conjugate acid or base.

2) Weak Acid + Strong Base (Acetic + NaOH):
In this case, acetic acid (CH3COOH) is a weak acid, and NaOH is a strong base. Weak acids do have buffering capacities because they only partially dissociate, leading to the formation of the weak conjugate base (CH3COO-) and a small concentration of H+ ions. When the strong base NaOH is added, the H+ ions react with the OH- ions to form water, resulting in the formation of the weak conjugate base.

3) Strong Acid + Weak Base (HCl + NH3):
Here, HCl is a strong acid, and NH3 is a weak base. Similar to the first combination, the strong acid will completely dissociate, leaving no significant concentration of the weak conjugate base.

4) Weak Acid + Weak Base (Acetic + NH3):
In this combination, both acetic acid and NH3 are weak acids and bases, respectively. Weak acids and bases can form buffers when mixed together because their ionization reactions are reversible. By mixing acetic acid and NH3, both the weak conjugate acid (NH4+) and the weak conjugate base (CH3COO-) will be present in the solution, allowing the formation of a buffer system.

Therefore, based on the analysis, the combination that would exhibit a buffering region in its plot is:

4) Weak Acid + Weak Base (Acetic + NH3)