Date: 25 Nov, 2004
1 ) To standardize sodium thiosulphate for titration use.
2 . To find out the concentration of Vitamin C in the tablet.
This kind of experiment entails titration of redox effect. Redox response means decrease and oxidation process. In which oxidizing agent and reducing agent are mixed and oxidize/reduce each other. A single losses electron(s) and embrace oxidation amount when is oxidized, and the other way round.
In order to find away concentration in the ascorbic acidity in the tablet, a redox reaction of it with iodine was completed. While iodine is a great oxidizing agent and ascorbic acid is a reducing agent. The reaction varieties dehydroascorbic acid and iodide.
Ascorbic acid + I2 -> dehydroascorbic acid + 2 H+ + 2 I-
Yet , Iodine does not dissolve in water very well. In this case, standard solution of potassium iodate(V) is used to make aqueous iodine. Excess potassium iodide and dilute sulphuric acid is usually added to react with potassium iodate.
KIO3 + 5 KI & 3 H2SO4 -> a few I2 & 3 WATER + 3 K2SO4
Excessive potassium iodide also helps dissolving iodine developed.
I-(aq) & I2(s) I3-(aq)
Iodine will not react with ascorbic acid too quickly, this is why they cannot be titrated immediately. We make use of excess iodine solution to react with limited vitamin C. Iodine still left is then titrated with salt thiosulphate, a reducing agent, thus range of mole of iodine responded with nutritional C can be found out. It is known as backside titration.
Sodium thiosulphate absorbs water inside the atmosphere with time. It's attention decreases over time as volume of water boosts. In this case, standization of salt thiosulphate is needed. Sodium thiosulphate is titrated with common iodine remedy, and the attention of it are available out.
a couple of Na2S2O3 + I2 -> Na2S4O6 + 2 NaI
Finally, when titrating with iodine, addition of starch solution is necessary. When Iodine is decreased to Iodide, its color turns by brown to pale yellow to colorless.
2 e- + I2(brown) -> a couple of I-(colorless)
It is rather hard to share whether the effect is completed. Consequently , we add starch option. Starch combines with iodine forming a blue complex which makes observation easier.
Potassium iodate(V) solid, salt thiosulphate soultion, 1 . 0M potassium iodide, 0. 5M sulphuric chemical p, starch solution, and Nutritional C tablet.
KIO3 is flammable and damaging. Rinse hands with a good amount of water when contacted with skin.
KIo3 solution produced is very limited and is needed to be used for equally titrations (That means 3+3=6 times) as being a of it can be used to rinse your pipette, just 9 times in total can be used, so there are only three times in excess pertaining to mistakes.
Weighing bottle of wine, electronic size, beaker, a glass rod, 250cm3 volumetric flask, filter funnel, dropper, pipette, white ceramic tile, conical flasks, measuring cyl
Preparation of common potassium iodate(V) solution
1 ) 0. 68g of potassium iodate(v) was weighed and was made up to 250 cm3 solution with the addition of water within a volumetric flask.
Standardization of Sodium Thiosulphate solution
installment payments on your Apparatus to get titration was set up.
several. Burette was rinsed with sodium thiosulphate solution.
four. A 25cm3 pipette was rinsed with potassium iodate(V) solution.
5. 25cm3 of KIO3 option was pipetted into a conical flask.
6. 5cm3 of 1M KI solution was added in the conical flask.
7. 10cm3 of 0. 5M Sulphuric acid was added in the conical flask.
8. Primary reading with the burette was recorded and the titration was started out.
9. Titration was ongoing until option in cone-shaped flask becomes pale yellow-colored, starch option was added.
10. Titration was ongoing until dark blue color has vanished.
11. Final Reading from the burette was recorded.
12. Steps 5 to 11 was repeated 3 times.
Determination with the Vitamin C content using standardized Sodium Thiosulphate option
13. A Vitamin C tablet was weighed and...
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