How many moles of S2O8^2- react for every mole of S2O3^2- that reacts? Consider the balanced chemical equations for reactions ( S2O8^2- + 2I2^- = 2SO4^2- + I2) and (I2 + 2S2O3^2- = 2I^- + S4O6^2- to calculate the changein concentration of S2O8^2- in this trial .


Screenshot 2024 01 17 173123

Screenshot 2024 01 17 173123

Step 1 of 2

Given is the how many moles of S2O8^2- react for every mole of S2O3^2- that reacts? Consider the balanced chemical equations for reactions (S2O8^2- + 2I2^- = 2SO4^2- + I2) and (I2 + 2S2O3^2- = 2I^- + S4O6^2- to calculate the change in concentration of S2O8^2- in this trial.

 

Table 1. Fictitious data for the iodine clock reaction at 21.50C.

Trial 0.200M NaI 0.200M Na2S2O3 0.00500 M Na2S2O3 1% Starch 0.100M K2SO4 0.100 M K2S2O8 DI Water Total Volume (mL) time (sec)
1. 16.0 35.0 21.0 13.0 42.0 9.00 4.00 1180

We found out the change in concentration of S2O82- in this trial.

Explanation:

Here we use the mole concept and law of Avogadro.

Step 2 of 2

As two balanced chemical reactions are given;

S2O82- + 2I2↽−−⇀2SO42- + I2

I2 + 2S2O32- ↽−−⇀ 2I + S4O62-

Overall

reaction

S2O82- + 2I2 + I2 + 2S2O32- ↽−−⇀ 2SO42- + I2 + 2I + S4O62-

Same reactant and product cut each other and final reaction becomes as the following,

S2O82- + 2I2 + 2S2O32- ↽−−⇀ 2SO42- + 2I + S4O62-

As seen in this final reaction for 1mol S2O82- requires 2mol of S2O32-

and for 1 mol of S2O32- there is requirements of 1/2 mol of S2O82-.

Final solution

So, we can say that for y mol of S2O82- requires 2y mol of S2O32-.

So, for 1 mol of S2O32- there is 1/2 mol of S2O82- is required for reaction.

 

 

 

 

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