Question

HA and \(\mathrm{HB}\) are both weak acids although \(\mathrm{HB}\) is the stronger of the two. Will it take more volume of a \(0.10 M \mathrm{NaOH}\) solution to neutralize \(50.0 \mathrm{~mL}\) of \(0.10 \mathrm{M}\) HB than \(50.0 \mathrm{~mL}\) of \(0.10 \mathrm{M}\) HA?

Short answer

No, it will not take more volume of \(0.10 M \mathrm{NaOH}\) solution to neutralize \(50.0 mL\) of \(0.10 M\) HB than \(50.0 mL\) of \(0.10 M\) HA. Irrespective of the strength, both acids will require an equal volume of sodium hydroxide solution for neutralization, given that they have the same volumes and molarities.

Step-by-step solution

Understanding acid-base neutralization

In acid-base neutralization, the reaction occurs on a 1:1 stoichiometric basis. This means for every mole of acid, we need one mole of base to neutralize it. Here, both acids are weak but it's irrelevant to the volume of base needed for neutralization.

Analyzing given concentrations and volumes

Both acids, HA and HB, have the same volume (50.0 mL) and concentration (0.10 M). Likewise, the sodium hydroxide solution that is used for neutralization also has a fixed concentration (0.10 M). Since the concentration and volume of the acids are the same, the same molar amounts of each acid are present.

Determining the volume of base needed

As established in step 1, the molar amount of base required for neutralization is equal to the molar amount of the acid. Therefore, the same volume of the sodium hydroxide solution will neutralize either of the acids, irrespective of their relative strengths. We do not need to perform any calculation as the answer is apparent from our understanding of the stoichiometry of neutralization reactions.

Forming the answer

The strength of an acid, in this case, doesn't affect the volume of a base needed for neutralization since all volumes and concentrations are the same. So the volume of the \(0.10 M \mathrm{NaOH}\) solution required to neutralize \(50.0 mL\) of \(0.10 M\) HA will be the same as that required to neutralize \(50.0 mL\) of \(0.10 M\) HB

Key concepts

Stoichiometry in Neutralization Reactions

Stoichiometry is a section of chemistry that involves calculating the quantities of reactants and products in chemical reactions. In the context of a neutralization reaction, stoichiometry is central to determining the volume of a base required to neutralize a given amount of an acid.

In simple acid-base reactions, stoichiometry often involves a 1:1 ratio, meaning that one mole of acid reacts with one mole of base. This is crucial in solving problems like the one in the exercise where equal molar amounts of two acids are being neutralized by a base. Despite the differences in strength between the weak acids, the stoichiometry dictates that if both solutions have the same molarity, the volume of base needed for neutralization will be the same for both acids.

To improve understanding, one might consider different scenarios where stoichiometry varies, such as a diprotic acid where one mole of acid reacts with two moles of base, thus the ratio becomes 1:2. Understanding these ratios helps in comprehending more complex reactions beyond simple 1:1 neutralizations.

Understanding Weak Acids

Weak acids are a group of acids that do not completely dissociate in water, meaning they do not donate all their hydrogen ions (H+) into the solution. This is contrary to strong acids, which fully dissociate and give up all their hydrogen ions.

When involved in neutralization reactions, weak acids react with strong bases to form water and a salt. However, because weak acids only partially dissociate, the pH of the solution does not change as dramatically compared to strong acids upon neutralization. Still, understanding that the weak acid’s reactivity in the solution is independent of the amount of base needed for neutralization is key.

Students often get confused by the strength of an acid and its implication on the volume of a base needed for neutralization. Reinforcing the fact that neutralization is stoichiometric and regardless of an acid's strength, identical concentrations and volumes of two acids will require the same amount of a base to be neutralized helps to clarify this point.

The Process of Titration

Titration is a laboratory technique used to determine the concentration of an analyte by reacting it with a titrant of known concentration. A typical titration of an acid with a base, also known as an acid-base titration, involves the gradual addition of the base to the acid solution until the reaction reaches the equivalence point, where the number of moles of acid equals the number of moles of base.

Titrations are often accompanied by an indicator, which changes color at the endpoint, signaling that the equivalence point has been reached. Understanding titration is essential as it emphasizes the concept of stoichiometry in a practical setting. Even when titrating weak acids, which may not have such a sharp endpoint due to their incomplete dissociation, understanding the stoichiometric relationship between the reactants allows the chemist to determine when neutralization has occurred.

Despite the exercise not explicitly involving a titration procedure, it draws on the same principles. Both weak acids HA and HB would reach their equivalence points after reacting with the same volume of NaOH due to the 1:1 stoichiometric relationship, making a direct connection to the titration process.