Question

Name the compound used in black and white photography. State whether the reaction that occurs is exothermic or endothermic. Give justification for your answer.

Answer 1

The compound commonly used in black and white photography is silver chloride (AgCl) or silver bromide (AgBr). The reaction that occurs is a photochemical decomposition reaction, which is endothermic. Justification: The decomposition of silver chloride (or silver bromide) into silver and chlorine (or bromine) occurs when light energy is absorbed. For example: \[ \text{2AgCl(s)} \xrightarrow{\text{Sunlight}} \text{2Ag(s) + Cl}_2\text{(g)} \] Since the reaction requires energy (in the form of light) to proceed, it is an endothermic reaction. Energy is absorbed from the surroundings (light) to break the bonds in AgCl. \[ Compound: Silver Chloride (AgCl) or Silver Bromide (AgBr).
Reaction: Endothermic.
Justification: Requires light energy for decomposition. \]