Question

Which of the following expressions is CORRECT for the rate of formation of Br₂?

\[\ce{5Br^-_{( aq)} + BrO^-_{3(aq)} + 6H^+_{( aq)} -> 3Br2_{(aq)} + 3H2O_{(l)}}\]

Options

• `(Δ["Br"_2])/(Δ"t") = 5 (Δ["Br"^-])/(Δ"t")`

• `(Δ["Br"_2])/(Δ"t") = 6/5 (Δ["H"^+])/(Δ"t")`

• `(Δ["Br"_2])/(Δ"t") = -1/2 (Δ["H"^+])/(Δ"t")`

• `(Δ["Br"_2])/(Δ"t") = -1/3 (Δ["BrO"_3^-])/(Δ"t")`

Answer 1

`(Δ["Br"_2])/(Δ"t") = -1/2 (Δ["H"^+])/(Δ"t")`

Explanation:

For the reaction,

\[\ce{5Br^-_{( aq)} + BrO^-_{3(aq)} + 6H^+_{( aq)} -> 3Br2_{(aq)} + 3H2O_{(l)}}\]

Average rate of reaction = `-1/5 (Δ["Br"^-])/(Δ"t")`

= `-(Δ["BrO"_3^-])/(Δ"t") = -1/6 (Δ["H"^+])/(Δ"t")`

= `1/3 (Δ["Br"_2])/(Δ"t") = 1/3 (Δ["H"_2"O"])/(Δ"t")`

∴ Rate of formation of Br₂, `(Δ["Br"_2])/(Δ"t") = -1/2 (Δ["H"^+])/(Δ"t")`