1. Clock Reaction (Initial rate method)

1.5. Procedure to determine the order of reaction with respect to S2O3(2-) ions

Experiment  \([H^+]\) / mol dm\(^{-3}\)  \(\text{S}_2\text{O}_3^{2-}\) / mol dm\(^{-3}\) Time (s)
1 0.001 0.001 120 
2 0.001 0.002 60

Calculate Rate of Reaction

Experiment  \([H^+]\) / mol dm\(^{-3}\)  \(\text{S}_2\text{O}_3^{2-}\) / mol dm\(^{-3}\) Time (s) Rate of Reaction (1/time)
1 0.001 0.001 120  \( \frac{1}{120} \approx 0.0083 \) s\(^{-1}\)
2 0.001 0.002 60 \( \frac{1}{60} \approx 0.0167 \) s\(^{-1}\)

W.r.t S2O32− and H+

Compare Expt 1 and Expt 2 where [H+] is the same.

When \([\text{S}_2\text{O}_3^{2-}]_{\text{Expt 2}}\) is twice of
\([\text{S}_2\text{O}_3^{2-}]_{\text{Expt 1}}\)
o Rate (2) is twice of rate (1)
o Order w.r.t \(\text{S}_2\text{O}_3^{2-}\) is one.