MCQs – Chemical Reactions and Equations class 10 science

Review

Question:  Which reaction is used in black and white photography?

Correct Answer

The decomposition reaction is used in the black and white photography. Photography paper contains either a layer of silver chloride or silver bromide, which when exposed to sunlight, decomposes and gives silver. This silver becomes grey in colour which print the impression of photograph on photography paper.

Reaction of Decomposition of Silver Chloride

When silver chloride (AgCl) is exposed in sunlight it decomposes into silver and chlorine and turns grey.

2AgCl(s) + Sunlight → 2Ag(s) + Cl₂(g)

Reaction of Decomposition of Silver Bromide

Silver bromide (AgBr) when exposed in sunlight decomposes into chlorine gas (Cl₂) and silver. This silver gives grey colour of photograph.

2AgBr(s) + Sunlight → 2Ag(s) + Br₂(g)

Since, in these reaction, decomposition take place, hence it is called decomposition Reaction.

And it is hence called that Decomposition Reaction takes place in black and white photography.