Question

What is the molarity of a potassium triiodide solution, KI3(aq), if 30.00 mL of the solution is required to completely react with 25.00 mL of a 0.300 M thiosulfate solution, K2S2O3(aq)? The chemical equation for the reaction is 2 S2O32-(aq) + I3-(aq) → S4O62-(aq) + 3 I-(aq).

Answer 1

Molarity of triiodide solution is 0.125M

Step-by-step explanation:

According to balanced equation, 2 moles of
`S_(2)O_(3)^(2-)` completely react with 1 mol of
`I_(3)^(-)`.

Moles of
`S_(2)O_(3)^(2-)` in 25.00 mL of 0.300 M of
`K_(2)S_(2)O_(3)` solution =
`(0.300* 0.02500)moles=0.0075moles`

So, 0.0075 moles of
`S_(2)O_(3)^(2-)` completely reacts with
`((1)/(2)* 0.0075)moles` of
`I_(3)^(-)` or 0.00375 moles of
`I_(3)^(-)`

If molarity of
`KI_(3)` solution is S (M) then-

`S* 0.0300=0.00375`

or,
`S=0.125`

So, molarity of triiodide solution is 0.125M