An aqueous solution containing 0.10 g `KIO_(3)` (formula weight`=214.0`) was treated with an excess of KI solution the solution was acidified with HCl. The liberated `I_(2)` consumed 45.0 " mL of " thiosulphate solution to decolourise the blue starch-iodine complex. Calculate the molarity of the sodium thosulphate solution.

Explanation

`2KIO_3+10KI+12H"Cl"to6I_2+6H_2O+12KCl`
`1 m" mol of "KIO_3-=3 m" mol of "I_2`
`implies of I_2=3xx(0.5)/(214)xx1000`
Also, 1 mmol `I_2-=2 mmol S_2O_3^(2-)`
`I_2+2S_2O_3^(2-)to2I^(ɵ)+S_4O_6^(2-)`
`impliesm" mol of "S_2O_3^(2-)-=2xx3xx(0.5)/(214)xx1000`
`implies` Molarity of `S_2O_3^(2-)-=((3000)/(214))xx(1)/(45)=0.3115`