What is the difference between the equivalence point and the end point in a titration?

The equivalence point is the theoretical point where the reactants are in exact stoichiometric proportions. The end point is the experimental point where the indicator actually changes color, which should ideally match the equivalence point.

When should a volumetric pipette be used instead of a burette?

A volumetric pipette is used when a single, highly accurate fixed volume (e.g., $25.0 \text{ cm}^3$) of a solution needs to be transferred. A burette is used when the volume required is unknown and must be measured variably during the reaction.

How does the calculation for a diprotic acid titration differ from a monoprotic one?

For a diprotic acid like $H_2SO_4$, the stoichiometric ratio with a base like $NaOH$ is $1:2$. This means you must double the moles of base to find the moles of acid, or vice versa, depending on the reaction direction.

What is a common error regarding the burette tip before starting a titration?

Leaving an air bubble in the burette tip is a common error. If the bubble dislodges during the titration, the recorded volume will be higher than the actual volume of liquid delivered, leading to an inaccurate titre.

Why is it a mistake to include the 'rough' titration in the calculation of the mean titre?

The rough titration is performed quickly to find the approximate end point and is usually less precise. Including it in the average reduces the accuracy of the final result; only concordant titres should be averaged.

What error occurs if the burette is rinsed with water instead of the titrant?

Rinsing with water dilutes the titrant remaining in the burette. This means a larger volume of the diluted solution will be needed to reach the end point, resulting in an incorrectly high calculated concentration for the analyte.

Define a 'standard solution' in the context of volumetric analysis.

A standard solution is a solution whose concentration is accurately known. It is used as the reference to determine the concentration of another substance through titration.

What are 'concordant results' in titration?

Concordant results are titres that are within a very close range of each other, typically within $0.10 \text{ cm}^3$. They indicate that the titration procedure is being performed consistently and reliably.

What is the 'titre' in a titration experiment?

The titre is the total volume of solution delivered from the burette to reach the end point. It is calculated by subtracting the initial burette reading from the final burette reading.

What is the formula used to calculate the number of moles from titration data?

The formula is $n = c \times V$, where $n$ is the number of moles, $c$ is the concentration in $\text{mol dm}^{-3}$, and $V$ is the volume in $\text{dm}^3$. Remember to divide $\text{cm}^3$ by $1000$ to get $\text{dm}^3$.

Library Podcasts

Courses

Referral & Rewards

Advanced Physical Chemistry

Titrations

Summary

Titration is a fundamental technique in volumetric analysis used to determine the unknown concentration of a solution by reacting it with a standard solution of known concentration. It relies on precise volume measurements and the identification of the equivalence point, where the reactants have combined in exact stoichiometric proportions.

1. Definition & Core Concepts

Volumetric Analysis: This is a quantitative chemical analysis method that involves measuring the volume of a solution of known concentration (standard solution) required to react completely with a measured volume of a solution of unknown concentration.
The Titration Process: A titration is the specific laboratory technique used to perform this analysis, typically involving the controlled addition of one reactant to another until the reaction is complete.
Equivalence Point: Also known as the stoichiometric point, this is the theoretical stage in a titration where the amount of titrant added is chemically equivalent to the amount of analyte in the sample.
End Point: This is the physical point in the titration where a visible change occurs, such as an indicator changing color, signaling that the equivalence point has been reached.

Diagram of a standard titration setup showing a burette positioned above a conical flask.

2. Apparatus & Precision

3. Methodology & Procedure

Preparation: The burette and pipette must be rinsed with the specific solutions they will contain to prevent dilution from residual water or contamination from previous experiments.
Titrating: The solution from the burette is added to the conical flask slowly, with constant swirling, until the indicator shows a permanent color change.
Concordancy: Multiple trials are performed until at least two results are concordant, meaning they are within $0.10 \text{ cm}^3$ of each other, to ensure reliability and precision.
The Rough Titre: The first trial is usually a 'rough' titration to find the approximate end point, allowing subsequent trials to be performed more carefully as the end point approaches.

4. Titration Calculations

5. Key Distinctions

6. Exam Strategy & Tips