Question

If you add NaOH to a solution containing 0.25 M acetic acid, will the concentration of protons increase or decrease?

Answer 1

The addition of NaOH to a solution of 0.25 M acetic acid will decrease the proton concentration due to the neutralization reaction between the acetic acid and the hydroxide ions. The presence of a buffer solution can mitigate the change in pH caused by the addition of a base like NaOH.

Step-by-step explanation:

If you add NaOH to a solution containing 0.25 M acetic acid, the concentration of protons (H+) will decrease. This is because NaOH is a strong base and will react with acetic acid following the equation: CH3CO2H(aq) + OH-(aq) → CH3CO2¯(aq) + H2O(l). In this neutralization reaction, hydroxide ions from NaOH react with the protons from acetic acid to form water, thereby decreasing the free proton concentration in the solution.

However, in the presence of a buffer, such as a mixture of acetic acid and its conjugate base, sodium acetate, the solution resists large changes in pH. The buffer works by absorbing excess protons or hydroxide ions. If the buffer concentration is high enough, such as at least 0.500 M, even the addition of a significant amount of NaOH, like 25 mL, will only cause a relatively small change in pH. This buffering effect is less pronounced at lower buffer concentrations.

Answer 2

Concentration of protons will decrease

Step-by-step explanation:

CH₃COOH + H₂O → CH₃COO⁻ + H₃O⁺

In a medium of water, acetic acid donates its proton to water, to increase the [H₃O⁺]

When we a add a strong base, like NaOH, this also dissociates as this:

NaOH → Na⁺ + OH⁻

As we are adding OH⁻, they will bond to H₃O⁺ so they be neutralized and they will produce water, that's why the [H₃O⁺] will decrease.

2H₂O ⇄ H₃O⁺ + OH⁻ Kw