Recall the reactions for this lab:

S2O82- + 2I- →
2SO42- + I2 (slow) Reaction 1
The one that delays the solution turning blue:
I2 + 2S2O32- → 2I- + S4O62- (fast) Reaction 2
b. All the S2O32 is consumed when the color change occurs. Therefore,

Δ[S2O32] =

c. Use the stoichiometry of Reactions 1 and 2 to determine the change in concentration of
S2O82- during the same time period.
Δ[S2O82-] =

d. Assuming the reaction took 75 seconds, calculate the rate of the reaction Δ [S2O82-]/Δt.
Rate of reaction = Δ[S2O82- ]/Δt =