Answer: Reduction of Ag+ to Ag 0 by light-generated electrons.
- A Oxidation of Ag+ to a higher silver oxidation state by absorbed light
- B Reduction of Ag+ to Ag<sup>0</sup> by light-generated electrons
- C Disproportionation of silver into two different oxidation states simultaneously
- D Direct oxidation of the silver ion by the halide ions present
Correct answer: B. Reduction of Ag+ to Ag<sup>0</sup> by light-generated electrons
Explanation: When light hits silver halide crystals, it excites electrons; these electrons reduce Ag⁺ ions to Ag⁰ atoms, forming a latent image. Ag⁺ is reduced (gains one electron) to metallic silver.
Electron transfer in a redox reaction: zinc loses electrons (oxidised, acts as reducing agent) and copper(II) ions gain those same electrons (reduced, acts as oxidising agent).
Concept context
Master electron transfer in chemistry: assign oxidation states, balance half-reactions, identify oxidising and reducing agents, and connect redox to everyday reactions.