Q1(m). Photochemical quantum yield

Answer in brief

Φ=1.18×10⁻² molecules decomposed per absorbed photon.

Key points

• The absorbed radiant energy is E_(abs)=0.60×250×90×60=8.10×10⁵ J.
• One photon has energy hc/λ=7.946×10⁻¹⁹ J. Therefore the amount of absorbed photons is E_(abs)/(N_Ahc/λ)=1.693 mol.
• Φ=n_(decomposed)/n_(photons,abs)=0.020/1.693=0.0118. Incident rather than absorbed photon count would give the wrong quantum yield.