Which of the following statements is true concerning the titration of a weak base by a solution of hydrochloric acid?
Question 9 options:
At the equivalence point, the pH is 7.
At the equivalence point, there is excess hydrochloric acid.
At the equivalence point, the pH is determined by the hydrolysis of chloride ion.
The solution is basic at the equivalence point.
The solution is acidic at the equivalence point.
The solution is acidic at the equivalence point due to the hydrolysis of the cation of the weak base.
To determine which of the statements is true concerning the titration of a weak base by a solution of hydrochloric acid, we need to understand the concept of titration and the properties of weak bases and hydrochloric acid.
Titration is a technique used to determine the unknown concentration of a solution by reacting it with a solution of known concentration. In this case, a weak base is being titrated with hydrochloric acid.
Now, let's examine each statement and determine its accuracy:
1. At the equivalence point, the pH is 7.
This statement is not true. The equivalence point is the point at which the moles of the acid and base being reacted are stoichiometrically balanced. In the case of titrating a weak base with hydrochloric acid, the equivalence point would be reached when all the weak base has reacted with the hydrochloric acid. Since hydrochloric acid is a strong acid, it completely dissociates in water, and its reaction with the weak base leads to the formation of a soluble chloride salt. The resulting solution at the equivalence point will have a pH that is determined by the nature of the salt formed.
2. At the equivalence point, there is excess hydrochloric acid.
This statement is true. At the equivalence point, all the weak base has reacted with the hydrochloric acid, and there is no further reaction occurring. Therefore, there will be excess hydrochloric acid present in the solution.
3. At the equivalence point, the pH is determined by the hydrolysis of chloride ion.
This statement is true. The pH at the equivalence point is determined by the nature of the salt formed from the reaction between the weak base and hydrochloric acid. In this case, the chloride ion, which is part of the salt formed, can undergo hydrolysis in water and affect the pH of the solution.
4. The solution is basic at the equivalence point.
This statement is not true. As we mentioned earlier, hydrochloric acid is a strong acid, and when it reacts with the weak base, it forms a salt. The nature of the salt formed determines the pH of the solution at the equivalence point. If the salt is derived from a weak base and a strong acid, it will result in an acidic solution.
5. The solution is acidic at the equivalence point.
This statement is true. Since hydrochloric acid is a strong acid, the reaction between the weak base and hydrochloric acid will result in the formation of a salt that is derived from a weak base and a strong acid. The presence of this salt in water can lead to the release of hydrogen ions, which makes the solution acidic.
Therefore, the correct statement is: The solution is acidic at the equivalence point.
In conclusion, to answer this question, we needed to understand the nature of titration, the properties of weak bases and hydrochloric acid, and the effect of the salt formed on the pH of the solution at the equivalence point.
The correct statement concerning the titration of a weak base by a solution of hydrochloric acid is:
At the equivalence point, there is excess hydrochloric acid.