Question

Predict whether the equivalence point of each of the following titrations is below, above, or at \(\mathrm{pH} 7\) : (a) \(\mathrm{NaHCO}_{3}\) titrated with \(\mathrm{NaOH}\), (b) \(\mathrm{NH}_{3}\) titrated with \(\mathrm{HCl}\), (c) KOH titrated with HBr.

Short answer

The equivalence point pH for the titrations are as follows: (a) NaHCO3 titrated with NaOH results in a pH greater than 7 due to a weak acid-strong base reaction. (b) NH3 titrated with HCl results in a pH less than 7 due to a weak base-strong acid reaction. (c) KOH titrated with HBr results in a pH equal to 7 due to a strong base-strong acid reaction.

Step-by-step solution

Titration (a) - NaHCO3 titrated with NaOH

NaHCO3 is a weak acid, and NaOH is a strong base. When a weak acid reacts with a strong base, the resulting solution will have a pH greater than 7. This is because the strong base dominates the reaction, and the resulting product has weak acidic and strong basic properties leading to a basic solution.

Titration (b) - NH3 titrated with HCl

NH3 is a weak base and HCl is a strong acid. In a titration of a weak base with a strong acid, the resulting solution will have a pH less than 7, as the strong acid will dominate the reaction and neutralize more of the weak base. The resulting product will have weak basic and strong acidic properties resulting in an acidic solution.

Titration (c) - KOH titrated with HBr

KOH is a strong base and HBr is a strong acid. In a titration of a strong base with a strong acid, the resulting solution should have a pH equal to 7. This is because both the strong base and the strong acid neutralize each other completely, resulting in a neutral salt.

Key concepts

Equivalence Point

The equivalence point in a titration is a significant moment. It is when the amount of titrant added equals the amount of substance present in the solution. At this point, the reactants have completely reacted with each other. This does not always mean that the solution has a pH of 7. The pH at the equivalence point depends on the nature of the acid and base involved.

• For strong acid-strong base titrations, the equivalence point is typically at pH 7.
• For weak acid-strong base titrations, the equivalence point is above pH 7.
• For weak base-strong acid titrations, the equivalence point is below pH 7.

Understanding the equivalence point is crucial, as it helps predict the pH of the solution after the reaction is complete.

Weak Acid and Strong Base Titration

When you titrate a weak acid with a strong base, interesting reactions occur. A weak acid, like \( ext{NaHCO}_3\), partially ionizes in solution. On the other hand, a strong base, such as \(\text{NaOH}\), fully dissociates.
This leads to the base dominating the reaction, which results in an equivalence point with a pH greater than 7.### Why is this important?

• It shows that the resulting solution is basic.
• It aids in understanding the behavior of weak acids in solutions.
• It's useful in laboratory settings for analytical purposes.

Overall, the weak acid and strong base titration underlines the importance of the ionic concentration and strength in determining the pH at the equivalence point.

Weak Base and Strong Acid Titration

Titrating a weak base with a strong acid gives different results. Weak bases, like \(\text{NH}_3\), don’t dissociate completely in a solution, while strong acids such as \(\text{HCl}\) do.
During titration, the strong acid neutralizes more of the weak base. This results in a solution with an equivalence point below pH 7.#### Highlights of this reaction

• The solution becomes acidic due to the dominance of the strong acid.
• The equivalence point gives insight into the buffering capacity of weak bases.
• This setup is common for precise pH measurements in scientific research.

Understanding weak base and strong acid titrations helps in grasping the fundamental interaction between acids and bases.

Neutralization Reaction

Neutralization reactions occur when an acid reacts with a base. In the case of a strong acid, like \(\text{HBr}\), and a strong base, such as \(\text{KOH}\), they neutralize each other completely.
The result is usually a salt and water with a pH of 7 at the equivalence point. However, the neutrality of the solution depends significantly on the strength of the acid and base involved. #### Key points about neutralization:

• In strong acid-strong base reactions, the products typically balance each other out.
• It is an essential concept in understanding how acids and bases react to form neutral solutions.
• This type of reaction is crucial in fields like chemistry and environmental science.

Neutralization forms the basis for how acid-base reactions are balanced by producing a neutral pH environment when both reactants are strong.