An aqueous solution containing 0.5 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 " mL of " thiosulphate solution to decolourise the blue starch-iodine complex. Calculate the molarity of the sodium thiosulphate solution. Also give a balanced chemical equation for the action of `KI` on `KIO_3`.

Explanation

`KIO_(3)+5KItoK_(2)O+3I_(2)`
Moles of `KIO_(3)=(0.1)/(214)`
Moles of iodine liberated`=3xx(0.1)/(214)`
`2Na_(2)S_(2)O_(3)+I_(2)to2NaI+Na_(2)S_(4)O_(6)`
Moles of `Na_(2)S_(2)O_(3)` requried `=3xx(0.1)/(214)xx2`
Molarity`=("Number of moles")/("Volume_(mL)")xx1000`
`=3xx(0.1)/(214)xx2xx(1)/(45)xx1000`
`=0.0623`