I wanted to solve initial concentration of iodine ion. however, the lab procedur

Question

I wanted to solve initial concentration of iodine ion.
however, the lab procedure said I should put 10 ml of deionized water and 10ml of 0.010M KI and 0.0010M Na2S2O3.
the other solutions in chegg, they says the initial volume is 20ml. why is that initial volume be 20ml ? instead of 10ml?
they all used 10ml of initial volume when they solved initial concentration of other ions except for I-
what am I missing here?
I'd be very appreciated if you can explain me why initial volume of the flask 1 is 20ml for Iodine ion.

Explanation / Answer

The total volume of reaction mixture (volume of flask 1 + volume of flask 2) must be 50 mL

For Trial 1, equal volumes of 4 components are taken, that is, 10 mL of KI + 10 mL of Na2S2O3 + 10 mL of KBrO3 + 10 mL HCl

Total becomes 40 mL. To make this 50 mL, 10mL of deionised water is added.

For Trial 2, volume of KI is 20 mL and volume of Na2S2O3 , KBrO3 and HCl is 10 mL each.

Total is 50 mL. Hence no need to add deionised water.

For Trial 3, volume of KBrO3 is 20 mL and volume of Na2S2O3 , KI and HCl is 10 mL each.

Total is 50 mL. Hence no need to add deionised water.

For Trial 4, volume of HCl is 20 mL and volume of KI, Na2S2O3 , and KBrO3 is 10 mL each.

Total is 50 mL. Hence no need to add deionised water.

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