Q15(b). Photolysis of HI: steady-state rate law and quantum yield
The photolysis of hydrogen iodide follows the mechanism: HI + hν → H• + I• (rate Ia); H• + HI → H₂ + I• (k₂); I• + I• → I₂ (k₃); H• + I₂ → HI + I• (k₄). Use the steady-state approximation to H• to construct the rate law. What is the overall quantum yield of the process?
Answer in brief
−d[HI]/dt = 2Ia k₂[HI]/(k₂[HI] + k₄[I₂]); overall quantum yield Φ = 2 early in the reaction.
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Coversphotolysis of HIsteady-state approximationquantum yieldphotochemical kineticsrate law
All parts of Question 15
- 15(a) B, I and the bond length of H³⁵Cl10 marks
- 15(b) Photolysis of HI: steady-state rate law and quantum yield10 marks