Question

Decomposition of HI has quantum yield = _______

(a) 1

(b) 2

(c) 0

(d) 4

This question was addressed to me in an internship interview.

I want to ask this question from Quantum Efficiency topic in section Photochemistry of Engineering Chemistry I

Answer 1

Correct answer is (b) 2

Best explanation: HI + hv→ H + I ……………….. Primary reaction                                                                                  H + HI → H2 + I

I + I → I2 …………….. Secondary reaction

Overall reaction: 2HI + hv → H2 + I2                                                                                                                          the overall reaction shows that 2 HI molecules are decomposed by 1 photon. So, quantum yield=2.