Titrimetric methods of analysis provide quick and easy analyte determinations with high accuracy and precision. It is based on the chemical reaction between the analyte, or known as titrand and a reagent, the titrant: aA + tT products where A and T represent the analyte and titrant, respectively, and a and t are the stoichiometric coefficients.
This type of reaction gives us with a simple means to classify titrimetry into the following four categories: acid–base titrations, in which an acidic or basic titrant reacts with a titrand that is a base or an acid; complexometric titrations based on metal–ligand complexation; redox titrations, where the titrant is an oxidizing or reducing agent; and precipitation titrations, in which the reaction between titrand and titrant form a precipitate.
…show more content…
Therefore, quantitative determination of the titrand concentration necessitate the following:
A. There must be stoichiometric reaction between analyte and titrant. This reaction should be fast and complete, and the values of a and t must be known.
B. CT must be known accurately. Standardization of titrant solution must be done either by using a primary standard or, by titrating it against a solution prepared with a primary standard.
C. The endpoint volume must be measured precisely using a suitable chemical indicator or instrumental method. If an instrumental method is used instead of indicator, a titration curve may be produced, which allows for the analysis.
Primary Standard and Secondary Standard
A primary standard is a highly purified compound that serves as the reference materials for a titrimetric method of analysis. Several important requirements for a primary standard
This lab contains two different procedures to titrating vinegar. One procedure uses phenolphthalein while the other uses a pH meter. Bothe procedures can be found on “An Analysis of a Household Acid: Titrating Vinegar” by the Department of Chemistry at APSU.
...d to mix the contents of the column. Aside from these commonalities, the instrumentation used varies greatly depending on the type of countercurrent chromatography used.
The purpose of the experiment is to determine the ID of an unknown diprotic acid by establishing its pKa values. The first phase is to determine the unknown diprotic acid by titration, which is a technique where a solution of known concentration is used to determine the molecular weight. While the second phase involved seeing how much NaOH needed to standardize diprotic acid.
A substance called an indicator is added to show the end of the titration. d. Clamp the buret on one side of the buret clamp. Place a white piece of paper labeled "Unknown Acid" under this buret. Drain any remaining pre-rinsed acid solution into a beaker labeled "waste solution". e. Fill this buret with your Unknown acid solution to the zero mark or slightly below it (Not above the zero mark).
Due to the nature of amino acids, a titration curve can be employed to identify
For this experiment, you will add the measured amount of the first sample to the measured amount of the second sample into its respectively labeled test tube then observe if a reaction occurs. In your Data Table, record the samples added to each test tube, describe the reaction observed, if any, and whether or not a chemical reaction took place.
However, there is no color change at end point of these reactions, so an indicator had to be added into the solutions to indicate the end point. An indicator is a chemical which is used to indicate the presence of the another substance in the solution; it changes colors when the ions H+ are added or removed by dissociation reaction. In this experiment, phenolphthalein was used as an indicator to indicate the presence of base in a solution by changing the color of the solution from colorless into pink. When the concentration of H+ is low, the solution becomes pink, and when the concentration of ions H+ is high, it becomes clear. The equivalent point is determined when there is a color change from colorless into light pink, and it is also an approximation of the end point. The concentrations were calculated by the equation M1V1 = M2V2, which means that the moles number of the base must equal to the moles number of an acid. The mole ratio in these reactions are 1:1 that means the moles’ number of the first reactant is equal to the moles’ number of the second one at the end
However, in order to measure the rates of reaction, sodium thiosulphate and starch are added. Sodium thiosulphate is added to react with a certain amount of iodine as it is made. Without the thiosulphate, the solution would turn blue/black immediately, due to the iodine and starch. The thiosulphate ions allow the rate of reaction to be determined by delaying the reaction so that it is practical to measure the time it takes for the iodine to react with the thiosulphate. After the all the thiosulphate has reacted with the iodine, the free iodine displays a dark blue/black colour with the starch. If t is the time for the blue/black colour to appear, then 1/t is a measure of the initial rate.
One of the most important things in caliometry is the caliometer. This is a device used to measure the quantity of heat in a reaction. There are many different types of caliometers, some are used to measure the heat capacity of materials, and others measure the aspects the heat generates by new or untested reactions, heat of combustion and burn rates. One type of caliometer is reaction caliometers. These measure heat energy released or absorbed during a reaction that occurs inside the caliometer. Bomb caliometer are used to measure heat of combustion of a particular reaction. Differential scanning caliometers heat flow into a sample is usually measured differentially. A popular caliometer used in biochemistry is called the isothermal titration caliometer. In this caliometer the heat of the reaction is used to follow a titration experiment. It is used in biochemistry because it t facilitates determination of substrate binding to enzymes. Other caliometers that are sometimes used are x-ray micocaliometer, and high-energy particle caliometer. These two caliometers are not as often used, but can still be included in the different types. It is apparent that there are many different types of caliometers and some are used more commonly than others
Complexometric Titrations [homepage on the internet]. No date. [ cited 2014 Mar 20]. Available from: http://www.ciens.ucv.ve:8080/generador/sites/martinezma/archivos/EDTA.pdf
This experiment consists of titrating the ferrous ion with permanganate ion to study the oxidation-reduction reaction. The ions react in acidic solution to give ferric ion and a reduced ionic form of manganese. All the reactants and products except permanganate ion are weakly colored, whereas permanganate is a very intensely colored ion. Then a solution of permanganate is removed as long as there is a ferrous ion present to react with it. But as soon as the entire ferrous ion has been oxidized, the next small portion of added permanganate colors the solution. The first appearance of a permanent pink color indicates the endpoint of the experiment. From the titration it will be able to calculate the percentage of iron in the sample from the data.
The pH of the analyte, in this case a strong acid like HCl, is plotted against the volume of the strong base, NaOH, that is being added. The titration of a strong acid with a strong base produces a titration curve as above.
Firstly, we need to keep the chemical at a constant concentration. So, in this experiment we have chosen to keep hydrochloric acid at a constant concentration (5cm3). We could have, however, used Sodium Thiosulphate as a constant, but we had chosen to use Hydrochloric acid. Next, we must make sure that the solution is kept at a constant volume throughout the experiment. If the volume is different, then it could give different results if it was at a constant volume.
In this experiment three different equations were used and they are the Stoichiometry of Titration Reaction, Converting mL to L, and Calculating the Molarity of NaOH and HCl (Lab Guide pg. 142 and 143).