To find the initial concentration of iodide (\(\mathrm{I}^-\)) in the reaction, use the dilution formula:
\[
C_{\text{initial}} = \frac{C_{\text{stock}} \times V_{\text{used}}}{V_{\text{total}}}
\]
Given:
- \(C_{\text{stock}} = 100.0 \, \text{mM}\)
- \(V_{\text{used}} = 10.0 \, \text{mL}\)
- \(V_{\text{total}} = 10.0 \, \text{mL} + 1.0 \, \text{mL} + 2.5 \, \text{mL} + 7.5 \, \text{mL} = 21.0 \, \text{mL}\)
\[
C_{\text{initial}} = \frac{100.0 \, \text{mM} \times 10.0 \, \text{mL}}{21.0 \, \text{mL}} = 47.6190 \, \text{mM}
\]
\(\boxed{47.6190 \, \text{mM}}\)
Using the same dilution formula for thiosulfate (\(\mathrm{S}_2\mathrm{O}_3^{2-}\)):
Given:
- \(C_{\text{stock}} = 31.5 \, \text{mM}\)
- \(V_{\text{used}} = 1.0 \, \text{mL}\)
- \(V_{\text{total}} = 21.0 \, \text{mL}\)
\[
C_{\text{initial}} = \frac{31.5 \, \text{mM} \times 1.0 \, \text{mL}}{21.0 \, \text{mL}} = 1.5000 \, \text{mM}
\]
\(\boxed{1.5000 \, \text{mM}}\)
Using the same dilution formula for hydrogen peroxide (\(\mathrm{H}_2\mathrm{O}_2\)):
Given:
- \(C_{\text{stock}} = 176.5 \, \text{mM}\)
- \(V_{\text{used}} = 7.5 \, \text{mL}\)
- \(V_{\text{total}} = 21.0 \, \text{mL}\)
\[
C_{\text{initial}} = \frac{176.5 \, \text{mM} \times 7.5 \, \text{mL}}{21.0 \, \text{mL}} = 63.0357 \, \text{mM}
\]
\(\boxed{63.0357 \, \text{mM}}\)
- Initial concentration of iodide in reaction: \(\boxed{47.6190 \, \text{mM}}\)
- Initial concentration of thiosulfate in reaction: \(\boxed{1.5000 \, \text{mM}}\)
- Initial concentration of hydrogen peroxide in reaction: \(\boxed{63.0357 \, \text{mM}}\)