A iodometric titration calculation?

1 g of KIO3{potassium iodate} is dissolved in water to gives a 250.00 cm^3 solution. 25.00cm^3 of potassium iodate is pippeted into a conical flask and add about 1.00cm^3 of 0.10gcm^-3 potassium iodine solution. and also add 0.1M sulphuric acid to acidified the mixture. {THUS, Iodine solution is liberatd} KIO3... show more 1 g of KIO3{potassium iodate} is dissolved in water to gives a 250.00 cm^3 solution.
25.00cm^3 of potassium iodate is pippeted into a conical flask and add about 1.00cm^3 of 0.10gcm^-3 potassium iodine solution. and also add 0.1M sulphuric acid to acidified the mixture. {THUS, Iodine solution is liberatd}

KIO3 + 5KI+3H2SO4====> 3K2SO4 + 3I2 + 3H2O

then the mixture solution is titrated with 25.00cm^3 of
sodium thiosulphate solution to reach the end point.
THe 1 cm^3 of 0.1 Gcm^-3 of starch is also added to the mixture when it is near the end point



HOW CAN I FIND THE the following a,b coefficient in the

equation?
aNa2S2O3 + bI2 ===> products where a and b are the

stoichiometric coefficients

we do not have the molarity of sodium thiosulphate, how can

I find the number of mole of sodium thiosulphate?
also why starch solution should be also freshly prepared?




potassium iodide turns yellow on standing in air.
account for this phenomenon with the u
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