A 1.0 M acetic acid solution (CH3COOH, pKa = 4.7) is neutralized by dissolving NaOH(s) (a strong base) in the solution. Estimate the pH at the equivalence point of the neutralization process:

4.7
7.0
9.3

Which one of the following statements best explains your prediction?

1. Since a weak acid does not react easily, higher basicity values are needed to fully neutralize it.
2. At the equivalence point, the most abundant specie in solution is the acetate ion, which acts as a base.
3. At equal concentrations of acid and base, the strong base is more dominant than the weak acid.
4. Neutralization means a neutral (pH = 7) solution.
Being a weak acid, the acetic acid doesn't produce as much H3O+(aq) as NaOH produces OH−(aq).

Let CH3COOH = HAc

.......HAc + NaOH = NaAc + H2O
At the equivalence point you have NaAc, sodium acetate. The acetate ion (C2H3O2^- or Ac^-) is hydrolyzed as follows and I assume that is solid NaOH placed in the acetic acid, there is no volume change, and (Ac^-) = 1M:
.........Ac^- + HOH ==> HAc + OH^-
I........1.0M............0.....0
C........-x..............x.....x
E........1.0-x...........x......x

Kb for Ac^- = (Kw/Ka for HAc) = (x)(x)/(1.0-x)
Solve for x = (OH^-) and convert to pH. I'll let you finish.

The reason is #2.

The correct answer is option 2: "At the equivalence point, the most abundant species in solution is the acetate ion, which acts as a base."

To understand why this option is correct, let's go through the process of neutralization and the concept of equivalence point.

Neutralization is a chemical reaction between an acid and a base, resulting in the formation of a salt and usually water. In this case, acetic acid (CH3COOH) is the acid and sodium hydroxide (NaOH) is the base. When they react, acetic acid donates a proton (H+) to the hydroxide ion (OH-) from NaOH, forming water (H2O) and acetate ion (CH3COO-). The acetate ion is a conjugate base of acetic acid.

The equivalence point is the point in a neutralization reaction where the stoichiometrically equivalent amounts of acid and base have reacted. At this point, all the acetic acid has been neutralized, and the most abundant species in solution is the acetate ion.

Since acetate ion is the conjugate base of acetic acid, it can react with water by accepting a proton (H+) to form acetic acid and hydroxide ion. This means that at the equivalence point, there will be a significant concentration of hydroxide ions (OH-) in the solution, making the solution more basic.

This is why the pH at the equivalence point is expected to be greater than 7. The pKa of acetic acid is 4.7, which indicates that acetic acid is a weak acid. A weak acid does not fully dissociate in water, so it does not produce as much H3O+ (hydronium ion) as a strong acid would. On the other hand, NaOH is a strong base and completely dissociates in water to produce a high concentration of OH- ions. Therefore, the strong base is more dominant than the weak acid at the equivalence point, resulting in a higher pH.

Hence, option 2 is the best explanation for the prediction of pH at the equivalence point.