Acid Base Titration Curve
Acid-base titration
Aim
To study the titration curve of a strong base-strong acid, strong base-weak acid and weak acid-strong base titrations
Introduction
Acid-base titrations are based on the neutralization reaction between the analyte and an acidic or basic titrant. When an acid and a base are present in a stoichiometric amount e.g. 1 mole HCl added to 1 mole NaOH, this means that the equivalent point has been reached in an acid-base system. The end point of an acid-base titration can be detected by the use of a pH indicator, a pH meter, or a conductance meter. The use of a pH meter to quantitatively determine the end point of a titration reaction is preferred to the use of visual indicator. This is because the pH meter monitors the change in pH at the equivalence point rather than just observing the color change in the visual indicator, and this eliminates the indicator blank errors. The use of a pH indicator is often regarded as tedious as compared to using visual indicators. However, knowing the expected endpoint makes the work much easier as one only has to concern themselves with dropwise addition towards the expected endpoint. A graph of pH vs volume of analyte added is used in determining the endpoint of the titration, which appears as a sudden change in pH.
In the titration of a strong acid with a strong base e.g. HCl with NaOH, the pH of the hydrochloric acid will change with the increasing amount of NaOH. At the end point the solution will become neutral with a pH of 7. This is only tru for strong acid-strong base titrations. For strong acid-weak base, weak acid-strong base and weak acid-weak base, the conjugate salt formed may undergo hydrolysis and act as a buffer solution shifting the pH at the end point away from 7. This is clearly visible when graphs of pH vs volume, or titration curves are drawn.
Apparatus
2 250 mL beaker
Stirrer and stir bar pH meter and combination electrode
100 mL burette
25 ml measuring cylinder
Aim
To study the titration curve of a strong base-strong acid, strong base-weak acid and weak acid-strong base titrations
Introduction
Acid-base titrations are based on the neutralization reaction between the analyte and an acidic or basic titrant. When an acid and a base are present in a stoichiometric amount e.g. 1 mole HCl added to 1 mole NaOH, this means that the equivalent point has been reached in an acid-base system. The end point of an acid-base titration can be detected by the use of a pH indicator, a pH meter, or a conductance meter. The use of a pH meter to quantitatively determine the end point of a titration reaction is preferred to the use of visual indicator. This is because the pH meter monitors the change in pH at the equivalence point rather than just observing the color change in the visual indicator, and this eliminates the indicator blank errors. The use of a pH indicator is often regarded as tedious as compared to using visual indicators. However, knowing the expected endpoint makes the work much easier as one only has to concern themselves with dropwise addition towards the expected endpoint. A graph of pH vs volume of analyte added is used in determining the endpoint of the titration, which appears as a sudden change in pH.
In the titration of a strong acid with a strong base e.g. HCl with NaOH, the pH of the hydrochloric acid will change with the increasing amount of NaOH. At the end point the solution will become neutral with a pH of 7. This is only tru for strong acid-strong base titrations. For strong acid-weak base, weak acid-strong base and weak acid-weak base, the conjugate salt formed may undergo hydrolysis and act as a buffer solution shifting the pH at the end point away from 7. This is clearly visible when graphs of pH vs volume, or titration curves are drawn.
Apparatus
2 250 mL beaker
Stirrer and stir bar pH meter and combination electrode
100 mL burette
25 ml measuring cylinder