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Tag Archives: titrimetry
Selecting an Indicator for a Redox Titration
The most important class of indicators for redox titrations are substances that do not participate in the redox titration, but whose oxidized and reduced forms differ in color. When we add a redox indicator to the titrand, the indicator imparts … Continue reading
Posted in Illustration
Tagged end point, equivalence point, indicator, titration curve, titrimetry
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Equivalence Points for Redox Titrations
For an acid–base titration or a complexometric titration, the equivalence point is almost identical to the inflection point near the middle of the steeply rising part of the titration curve, which makes it relatively easy to locate the equivalence point … Continue reading
Spectrophotometric Titrations
If at least one species in a complexation titration absorbs electromagnetic radiation, we can identify the end point by monitoring the titrand’s absorbance at a carefully selected wavelength. For example, we can identify the end point for a titration of … Continue reading
Posted in Illustration
Tagged end point, equivalence point, spectrophotometric titration, titration curve, titrimetry
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Indicators for Complexation Titrations
Most indicators for complexation titrations are organic dyes—known as metallochromic indicators—that form stable complexes with metal ions. The indicator, Inm–, is added to the titrand’s solution where it forms a stable complex with the metal ion, MInn–. As we add … Continue reading
Posted in Illustration, Photo
Tagged complexation titration, EDTA, end point, indicator, titrimetry
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Microtitrations
The illustrations below show two approaches to titrating very small samples. In the first experimental design, samples of 20–100 µL were held by capillary action between a flat-surface pH electrode and a stainless steel sample stage. The titrant was added by … Continue reading
Limitations to Acid-Base Titrations
In an acid–base titration the volume of titrant needed to reach the equivalence point is proportional to the moles of titrand. Because the pH of the titrand or the titrant is a function of its concentration, however, the change in … Continue reading
Determining an Acid Dissociation Constant from a Titration
Another application of acid–base titrimetry is the determination of equilibrium constants. Consider, for example, a solution of acetic acid, CH3COOH, for which the dissociation constant is Ka = [H3O+][CH3COO–]/[CH3COOH] When the concentrations of CH3COOH and CH3COO– are equal, the Ka expression reduces … Continue reading
Finding the Equivalence Point From a Titration Curve
An alternative to using a visual indicator to locate a titration’s end point is to continuously monitor the titration’s progress using a sensor whose signal is a function of the analyte’s concentration. The result is a plot of the entire … Continue reading
Visual Indicators for Acid-Base Titrations
The illustration below shows the relationship between pH and an indicator’s color. The ladder diagram defines pH values where each of the indicator’s two forms the weak acid form, HIn, which in this example is yellow the weak base form, … Continue reading
Posted in Illustration, Photo
Tagged acid-base indicator, acid-base titration, end point, equivalence point, indicator, titrimetry
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Locating a Titration’s Equivalence Point
For most acid–base titrations the inflection point, the point on a titration curve having the greatest slope, very nearly coincides with the equivalence point. The red arrows in the following figure for example, indicate the equivalence points for the titrations … Continue reading