A student investigates the reaction between persulfate ions and iodide ions at constant temperature.

\[ \text{S}_2\text{O}_8^{2-}\text{(aq)}+2\text{I}^-\text{(aq)}\rightarrow \text{I}_2\text{(aq)}+2\text{SO}_4^{2-}\text{(aq)} \]

The experimentally determined rate law is

\[ \text{rate}=k[\text{S}_2\text{O}_8^{2-}][\text{I}^-] \]

At \(t=0\text{ min}\), the concentrations are \([\text{S}_2\text{O}_8^{2-}]=1.00\times10^{-2}\text{ M}\) and \([\text{I}^-]=1.00\text{ M}\). Even if all the persulfate reacts, \([\text{I}^-]\) decreases by no more than \(2.0\%\). The student observes that \([\text{S}_2\text{O}_8^{2-}]\) decreases to \(5.00\times10^{-3}\text{ M}\) after \(20.0\text{ min}\). Which prediction for \([\text{S}_2\text{O}_8^{2-}]\) at \(t=60.0\text{ min}\) is most nearly correct, and why?