Acid Base Titration

An acid-base titration is a quantitative analysis of acids and bases in which an acid or base of known concentration neutralizes an acid or base of unknown concentration; in this process, an acid or base of known concentration neutralizes an acid or base of unknown concentration.

Visual indicators, pH electrodes, or a combination of the two can be used to track the titration progress.

At the equivalence point, the amount of acid or base present in the unknown analyte has been completely neutralized. If you know the amount of acid or base present in the unknown solution, you can calculate its concentration using the volume and concentration of titrant present at the equivalence point.

Using the pH of the analyte solution and the acid dissociation constant (pKa) of the acid or the base dissociation constant (pKb) of the base in the analyte solution, it is possible to determine the concentration (molarity) of the analyte solution. An alternative method for deducing the pKa is to construct a titration curve with a known solution concentration in the case of analyte solutions with unknown concentrations.

Alkalimetry and acidimetry:

Alkalimetry and acidimetry are both types of volumetric analysis in which the fundamental reaction is a neutralization reaction, as opposed to other types of volumetric analysis. Acidimetry is the specialized analytic application of acid-base titration to determine the concentration of a basic (synonymous to alkaline) substance by using a standard acid as a starting point. In alkalimetry, the same concept as specialized analytic acid-base titration is applied, but this time to an acidic substance using standard base instead of a standard acid.

Indicator choice:

 In order to detect the end point of the titration, it is necessary to use a pH indicator that is appropriate for the situation. The colour change or other effect should occur close to the equivalence point of the reaction in order for the experimenter to be able to accurately determine when the equivalence point has been reached. Following are some guidelines for estimating the pH of the equivalence point.

• In the presence of a strong acid, a strong base will react to form a neutral (pH = 7) solution.
• In the presence of a strong acid, a weak base will react to form an acidic solution (pH less than 7).
• A weak acid will react with a strong base to form a basic solution (pH > 7) when the two react together.

If the two substances are of equal strength, the equivalence pH will be neutralized. It is rare for weak acids to be used in titration against weak bases because the color change indicated by the indicator is often rapid, making it difficult for the observer to notice the change in color.

The end point is the point at which the indicator’s color changes.

Acid base titration curve and diagram:

In a titration, the equivalence point is the point at which the same amount of moles of hydroxide ions have been added as there are moles of hydrogen ions has been added exactly once more. It is possible to perform a titration if the base is added from the burette and the acid has been precisely measured into a flask. Each titration curve has a characteristic shape that corresponds to the type of acid-base titration being performed.

The pH of the solution does not change in a predictable manner as the acid is introduced. Each curve contains horizontal sections where a large number of bases can be added without significantly altering the pH. Except for weak acid and weak base, where a single drop of base can cause the pH to change by several units, each curve has a steep portion, with the exception of weak acid and weak base. Despite the fact that the equivalence point is not centred on pH 7, there is a significant change in pH at this point. This is important when deciding on the indicators to use for each type of titration.

Conclusion:

It is a quantitative analysis method that determines the concentration of an acid or base by exactly neutralising it with a standard solution of base or acid that has a known concentration in the solution under test. The progress of the acid–base reaction is monitored with the help of a pH indicator. An acid-base titration is a quantitative analysis of acids and bases in which an acid or base of known concentration neutralises an acid or base of unknown concentration. 

In the presence of a strong acid, a strong base will react to form a neutral (pH = 7) solution. In the presence of a strong acid, a weak base will react to form an acidic solution (pH less than 7). A weak acid will react with a strong base to form a basic solution (pH > 7) when the two react together. 

It is possible to perform a titration if the base is added from the burette and the acid has been precisely measured into a flask. Each titration curve has a characteristic shape that corresponds to the type of acid-base titration being performed.