Table of Contents
Why is kio3 used in titration?
Potassium iodate is often used as a reference material to standardize a sodium thiosulfate solution which is a familiar titrant for redox titrations. In the standardization, iodine (triiodide) liberated by potassium iodate in an acidic potassium iodide solution is titrated with a sodium thiosulfate solution.
How do you titrate ascorbic acid?
Titrating Juice Samples
- Add 25.00 ml of juice sample to a 125 ml Erlenmeyer flask.
- Titrate until the endpoint is reached. (Add iodine solution until you get a color that persists longer than 20 seconds.)
- Repeat the titration until you have at least three measurements that agree to within 0.1 ml.
What happens to vitamin C during iodometric titration?
Vitamin C, more properly called ascorbic acid, is an essential antioxidant needed by the human body (see additional notes). As the iodine is added during the titration, the ascorbic acid is oxidised to dehydroascorbic acid, while the iodine is reduced to iodide ions.
Which indicator is used for the titration of ascorbic acid?
phenolphthalein
Ascorbic acid can be titrated with a base (sodium hydroxide, NaOH) using the indicator, phenolphthalein.
Why is KIO3 a good primary standard?
Potassium Iodate is an oxidizing agent and a good primary standard with the one drawback of having a relatively low equivalent weight. It is used primarily as a stable source of Iodine, which is liberated in the presence of Iodide ion and acid, in the titration of Thiosulfate and Sulfite solutions.
Is KIO3 soluble?
Soluble in water at 4.74 g/100 ml(0°c); 9.16 g/100 ml(25°c); 32.3 g/100 ml(100°c). KIO3 is soluble in kl solution. KIO3 is insoluble in alcohol, liquid ammonia, and nitric acid.
Why is kio3 a good primary standard?
Why the determination of ascorbic acid is done using iodometric acid?
Ascorbic acid determination was carried out by iodine titration. When iodine is added to a starch solution, it reacts to produce a purple color. However, if there is any vitamin C in the solution, it “neutralizes” the iodine, preventing the formation of the purple color.
Why does vitamin C turn iodine clear?
If vitamin C is present, the brownish color of the iodine solution will become colorless — the vitamin C serves as a reducing agent and reduces iodine to iodide ions (colorless in solution).
Why is back titration used in ascorbic acid?
A part of iodine (as triodide ions) is consumed for the oxidation of ascorbic acid and the remaining excess of iodine is determined by titrating with a standard solution of sodium thiosulphate. Such an indirect determination is called back titration. As you are aware, iodine forms a violet coloured complex with starch.
Which colour appears at the end of titration?
In an iodometric titration, a starch solution is used as an indicator since it can absorb the I 2 that is released. This absorption will cause the solution to change its colour from deep blue to light yellow when titrated with standardised thiosulfate solution. This indicates the end point of the titration.
How do you standardize KIO3?
Potassium Iodate Solution Standardization
- Dilute 25.0 ml of the solution to 100 ml with water.
- To 20.0 ml of this solution add 2 g of potassium iodide and 10 ml of 1M sulphuric acid.
- Titrate with 0.1 M sodium thiosulphate using 1 ml of starch solution, added towards the end of the titration, as an indicator.
Why is KIO3 an oxidizing agent?
Potassium iodate is an oxidising agent and as such it can cause fires if in contact with combustible materials or reducing agents. The chemical formula for potassium iodate is KIO3. It can be prepared by reacting potassium base with iodic acid.
Does ascorbic acid react with HCL?
ON adding hydrochloric acid to a solution of ascorbic acid, reversible oxidation with 2: 6-dichloro-phenolindophenol and iodine becomes progressively slower as the mineral acid content increases.
What are the different methods of estimation of ascorbic acid?
In addition, there are many analytical methods used to determine the concentration of vitamin C in the pharmaceutical samples which are colorimetric method, titration, enzymatic method, Flow Injection Analysis (FIA) and High Performance Liquid Chromatography (HPLC) (Arya and Mahajan, 1997).
How do you oxidize ascorbic acid?
Ascorbic acid is a well-known antioxidant and radical scavenger. It can be oxidized by losing two protons and two electrons, but normally loses only one electron at a time.
How does ascorbic acid react with iodine?
When ascorbic acid reacts with iodine, the ascorbic acid is oxidized (looses electrons) and the iodine is reduced (gains electrons). As long as the solution contains ascorbic acid, the iodine is used up in a rapid. reaction with ascorbic acid, during which dehydroascorbic acid and iodide ion are formed.
Remember, that you may need to do a test titration before deciding on the sample size. Pipette aliquot of the ascorbic acid solution into Erlenmeyer flask (100 or 200 mL, depending on the sample volume). Add 5 mL of starch solution. Titrate with iodine solution until a faint blue color persists after 20 seconds of swirling the solution.
What type of reaction takes place during titration of vitamin C?
Reaction taking place during titration is: where C 6H 😯 6 is ascorbic acid (vitamin C) and C 6H 6O 6 is dehydroascorbic acid. sample size. For 0.05 M titrant and assuming 50 mL burette, aliquot taken for titration should contain about 0.61-0.80 g of ascorbic acid (3.5-4.5 millimoles).
What is the reaction between ascorbic acid and iodine?
In the cells it is easily oxidized to dehydroascorbic acid, removing oxidizing agents before they can do damage to other substances present. This reaction is the basis of the iodometric titration of ascorbic acid – it is quantitatively oxidized by iodine.
Why is a redox reaction better than an acid-base titration?
The redox reaction is better than an acid-base titration since there are additional acids in a juice, but few of them interfere with the oxidation of ascorbic acid by iodine. Iodine is relatively insoluble, but this can be improved by complexing the iodine with iodide to form triiodide: