Titration experiments are amongst the most common laboratory experiments performed in chemistry. They’re designed to indirectly measure the concentration of a substance (analyte) by gradually adding another substance (titrant).
You’ve probably performed a titration experiment at school and in your academic studies. While the substances and concentrations may vary, the fundamental techniques are essentially the same.
An indicator, such as litmus paper, is typically used to determine the threshold of a chemical reaction. The indicator changes colour when a certain chemical reaction threshold, or end point of titration, is reached.
As we explain below, there are four main types of titration experiments in chemistry: acid-base titration, precipitation titration, complex-formation titration, and oxidation-reduction titration (redox).
In this post:
How to carry out a titration experiment
Titration experiments generally use burettes to gradually add a standard solution (a substance of known concentration) to a substance of unknown concentration. The solution that’s slowly added is called the titrant while the substance of unknown concentration is called the analyte.
A colour-changing indicator is added to determine the threshold of reaction (the point at which neutralisation occurs). In other cases, an instrument like a pH metre is used to establish the point of neutralisation. Sometimes precipitates may also form to indicate the end of titration.
Do you have to duplicate titration experiments?
Accuracy and precision are important in any experiment. You’ll therefore need several samples of data to verify the reliability of your results.
If you want to be confident that your titration experiments are accurate and precise, you should repeat them at least three times per analyte. If the results are the same or very close to each other, you’ll know your measurements are correct.
How reliable is a titration experiment?
When done correctly, a titration experiment is very reliable. To be considered accurate or reliable, you’ll need to ensure you have very precise measurements and repeatable results.
As a starting point, you might want to perform a scout titration to get a rough estimate of the reaction endpoint. It’s a less precise form of titration, but you can use it as a baseline for your actual titration experiment. In a scout titration, a pipette is used to introduce a titrant into a solution of analyte.
What are the 4 types of titration?
There are four types of titration experiments based on the reactants and products involved. These are known as acid-base titration, precipitation titration, complex-formation titration, and oxidation-reduction titration (redox).
The most common type of titration experiment is the reaction between a strong acid and a strong base. The endpoint is reached when the pH becomes neutral. The generalised chemical equation for this reaction is:
Acid + Alkali→Salt + Water
Or H+ + A– + B+ + OH– → B+ + A– + H2O
Or H+ + OH– → H2O
The final product or products of this type of titration are insoluble solids that precipitate. For example, the titration of a chloride solution with silver nitrate produces silver chloride as a precipitate, while ammonium thiocyanate and silver nitrate forms silver thiocyanate.
AgNO3 + NaCl → AgCl + NaNO3
AgNO3 + NH4CNS → AgCNS + NH4NO3
Complex-formation titration, otherwise known as complexometric titration, involves the formation of an undissociated complex at the equivalence point. Some examples are shown below:
Hg2+ + 2SCN– → Hg(SCN)2
Ag+ + 2CN– → [Ag(CN)2]–
Ethylenediaminetetraacetic acid (EDTA) is commonly used as a reagent in the formation of metal complexes.
Oxidation-reduction, or redox titration, transfers electrons in a chemical reaction. In this case, an oxidising agent takes away electrons from the reduction agent. Oxidation-reduction titration experiments are generally grouped according to which reagent is being used. Some of the most common redox titrations include:
- Permanganate titrations
- Dichromate titrations
- Iodimetric and iodometric titrations
The dangers of titration experiments
Titration experiments usually involve handling corrosive, toxic, and hazardous substances. The main dangers posed by performing these types of experiments are chemical burns and poisoning. It’s therefore essential to take the proper safety precautions, for example, by wearing goggles, gloves, and lab gowns to protect you from potentially dangerous chemicals.
Titration is a relatively straightforward process that involves two reactants – the titrant and the analyte. It’s a volumetric laboratory method that’s used to determine the molar concentration of an analyte (the solution being identified). The four main types of titration experiments are acid-base titration, precipitation titration, complex-formation titration, and oxidation-reduction titration (redox).
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