Question

End point in acid base titration is the point where (1) the base is added to the acid (2) the base is exactly neutralized with acid (3) the acid is found in slight excess (4) none

Short answer

The end point in acid-base titration is the point where the base is exactly neutralized with acid.

Step-by-step solution

Understanding Acid-Base Titration

Acid-base titration is a procedure where a solution of known concentration (titrant) is used to determine the concentration of an unknown solution.

Definition of the End Point

The end point of a titration is the point at which the indicator changes color, signifying that the equivalent amount of titrant has been added to react completely with the analyte.

Neutralization Concept

In an acid-base titration, the end point closely approximates the point where the amounts of acid and base are stoichiometrically equivalent, called the equivalence point.

Conclusion Based on Options

Option (2) states that the base is exactly neutralized with acid, which corresponds to the definition of the end point in the context of an acid-base titration.

Key concepts

End Point

In an acid-base titration, the end point is a crucial concept. It signifies the moment when the indicator changes color. This visual change marks that the titration process is practically complete. The end point is important because it indicates that the amount of titrant added is adequate to react completely with the analyte. For example, if you are titrating a base with an acid, the end point is reached when the amount of acid added neutralizes the base present.

To achieve accurate results in a titration, it's important to choose an appropriate indicator that changes color close to the solution's equivalence point. This ensures that the observed color change closely reflects the point of neutralization.

Neutralization

Neutralization is a fundamental concept in chemistry, describing the reaction between an acid and a base to form water and a salt. During acid-base titration, neutralization signifies that equal moles of acid and base have reacted. The reaction can be represented as: \[ H^+ + OH^- \rightarrow H_2O \]Where the hydrogen ions from the acid combine with the hydroxide ions from the base to form water.
This process is both important and predictable:

• Results in a pH change
• Forms water and a salt

Once neutralization is achieved, no excess hydrogen or hydroxide ions remain in the solution.

Equivalence Point

The equivalence point is where stoichiometric amounts of acid and base have reacted. It's slightly different from the end point and is a theoretical concept indicating the direct proportionality between acid and base in the reaction. Unlike the end point, which is often detected by a color change in an indicator, the equivalence point is determined based on the reaction's stoichiometry.
For example, in the titration of hydrochloric acid (HCl) with sodium hydroxide (NaOH), the equivalence point is the precise moment when \[ moles \, of \, HCl = moles \, of \, NaOH \].

• Indicator color change should ideally coincide with equivalence point
• It's critical for accurate titration results

Titrant

The titrant is a solution of known concentration used to determine the concentration of an unknown solution during titration. It is gradually added to the analyte solution until the reaction reaches the end point. The volume of the titrant used helps calculate the unknown concentration based on the known volumes and concentrations. Typical titrants include strong acids like HCl or strong bases like NaOH, depending on the nature of the analyte. The titrant's role is essential:

• Drives the titration process
• Must be accurate and precisely measured

Ensuring the titrant is properly standardized is key to obtaining reliable titration results.