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In the titration of 12 (aq) by S2 O3^(2-...

In the titration of `1_2` (aq) by `S_2 O_3^(2-) (aq)` using the starch indicator, the end point is indicated by

A

colourless to blue

B

blue to colourless

C

pink to colourless

D

blue to pink

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Verified by Experts

The correct Answer is:
B
The chemical reaction involved during the titration of `I_(2)(aq)` by `S_(2)O_(3)^(2-)(aq)` using starch indicator is
`I_(3)^(-)+2S_(2)O_(3)^(2-)toS_(4)O_(6)^(2-)+3I^(-)`
At the end point deep blue colour disappears due to the decomposition of the iodine-starch complex, Thus, the colour change at end point is from blue to colourless.
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Iodine titration can be iodemotric or iodimetric depending on using iodine directly or indirectly is an oxidising agent in the redox titration. a. Iodimetric titration in which a standard iodine solution is used as an oxidant and iodine is directly or indirectly titrated against a reducing agent. For example. 2CuSO_(4)+4KJtoCu_(2)I_(2)+2K_(2)SO_(4)+I_(2) b. Iodimetric procedures are used for the datermination of strength of reducing agent such as thiosulphates, sulphites, arsenties adn stanous chloride etc. by titrating them against standard solution of iodine in a burette. 2Na_(2)SO_(3)to2 NaI +Na_(2)S_(4)O_(6) Starch is used as indicator near the end point whilch form blue colour complex with I_(3)^(-) . The blue colour disappeams when there is not more of free I_(2) . The volume of KI solutioin used for CuSO_(4) will be

All titration which involves the direct titration of Iodine with a reducing agent are grouped under lodimetry. Iodimetry is employed to determine the strength of reducing agent such as sodium thio sulphate I_(2) + 2Na_(2)S_(2)O_(3) rarr 2I^(-)+S_(4)O_(6)^(-) If iodine is liberated as a result of chemical reaction involving oxidation of an idodide ion by a strong oxidizing agent in neutral or acidic medium the liberated iodine is then titrated with reducing agent. This titration is called lodometry. Todometry is used to estimate the strength of oxidizing agent. For example the estimation of Cu^(++) with thiosulphate. Cu^(+ +) +I^(-) Cu_(2)I_(2)+I_(2) , I_(2) +S_(2)O_(3)^(-) rarrS_(4)O_(6)^(-) +I^(-) Starch used as indicator near the end point which form blue colour complex with I_(3)^(-) . The blue colour disappears when When 159.50g of CuSO_4 in a solution is reacted with KI, then the liberated iodine required 100 ml 1 M Na_(2)S_(2)O_3 for complete reaction, then what is the percentage purity of sample used in making the solution.

All titration which involves the direct titration of Iodine with a reducing agent are grouped under lodimetry. Iodimetry is employed to determine the strength of reducing agent such as sodium thio sulphate I_(2) + 2Na_(2)S_(2)O_(3) rarr 2I^(-)+S_(4)O_(6)^(-) If iodine is liberated as a result of chemical reaction involving oxidation of an idodide ion by a strong oxidizing agent in neutral or acidic medium the liberated iodine is then titrated with reducing agent. This titration is called lodometry. Todometry is used to estimate the strength of oxidizing agent. For example the estimation of Cu^(++) with thiosulphate. Cu^(+ +) +I^(-) Cu_(2)I_(2)+I_(2) , I_(2) +S_(2)O_(3)^(-) rarrS_(4)O_(6)^(-) +I^(-) Starch used as indicator near the end point which form blue colour complex with I_(3)^(-) . The blue colour disappears when 10 mL of H_2O_2 solution on treatment with KI and titration of liberated I_2 required 10 mL of 1 N hypo . Thus H_2O_2 is :

50 ml solution of H_(2)O_(2) was treated with excess KI (s) and the solution was acidified with acetic acid. The liberated I_(2) required 40 ml of 0.5 M Na_(2)S_(2)O_(3) solution for the end point using starch is indicator. Find the molairty and volume strength of the H_(2)O_(2) solution.

The end point of iodometic titrations is detected by adding starch just near end point and not all the beginning of titration. Which statement is not valid for this falt?

I_(2(aq))+2S_(2)O_(3(aq))^(-2) to 2I_((aq))^(-)+S_(4)O_(6(aq))^(2-) For the above titrimetric reaction how is the end point determined?

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