Q4(a)(i). Stark–Einstein law; why the quantum yield is often low
State and explain Einstein law of photochemical equivalence. How is low quantum yield explained?
Answer in brief
Each molecule that takes part in the primary photochemical step absorbs one quantum of light (hν); one mole absorbs one einstein, NA hν. The quantum yield φ (molecules reacted ÷ photons absorbed) is low when excited molecules lose their energy (fluorescence, collisions, internal conversion) or their fragments recombine before forming product.
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All parts of Question 4
- 4(a)(i) Stark–Einstein law; why the quantum yield is often low10 marks
- 4(a)(ii) Surface area of silica gel from the nitrogen monolayer10 marks
- 4(b) Standard and actual potential of the Cu / Fe³⁺, Fe²⁺ cell10 marks
- 4(c) Schrödinger wave equation in three dimensions; meaning of ψ and ψ²10 marks