Question

Consider the reaction of peroxydisulfate ion (S2O82-) with iodide ion (I -) in aqueous solution.

S2O82-(aq) + 3 I -(aq) ¨ 2 SO42-(aq) + I3-(aq)

At a particular temperature, the rate of disappearance of S2O82- varies with reactant concentrations in the following manner.

Experiment [S2O82- ] (M) [I - ] (M) (M/s)
1 0.018 0.036 2.6 10-6
2 0.027 0.036 3.9 10-6
3 0.036 0.054 7.8 10-6
4 0.050 0.072 1.4 10-5

I got the rate constant to be .004 by the rate = k[S2O82-] . [I-]

but i have no idea how to get What is the rate of disappearance of I - when [S2O82- ] = 0.022 M and [I - ] = 0.042 M?
please help me and explain if possible

Answer 1

The rate of disappearance of I- when [S2O82-] = 0.022 M and [I-] = 0.042 M can be calculated using the rate constant you found. The rate of disappearance of I- is equal to the rate constant multiplied by the concentrations of S2O82- and I-:

Rate = k[S2O82-] . [I-]

Rate = 0.004 (0.022 M)(0.042 M)

Rate = 3.168 x 10-5 M/s