MCQs – Chemical Reactions and Equations class 10 science

Review

Question:  What happens when silver chloride is put under sunlight?

Correct Answer

When silver chloride is put under sunlight, it gives silver (Ag) metal and Chlorine (Cl₂) gas.

2AgCl(s) + Sunlight → 2Ag(s) + Cl₂(g)

In this reaction silver chloride turns into grey due to sunlight. This happens because of formation of silver metal.

This reaction is used in the black and white photography

Here, since silver chloride decomposes after getting sunlight, hence this reaction is called Thermal Decomposition and/or Decomposition Reaction. And since here reaction is carried out after getting of heat in the form of light, hence it is an Endothermic Reaction also.

The other similar reaction is the thermal decomposition of silver bromide into silver metal and bromine gas after getting exposed to sunlight.

2AgBr(s) + Sunlight → 2Ag(s) + Br₂

In this reaction also silver bromide turns into grey colour because of decomposes into silver (Ag) metal.

This reaction is also used in black and white photography

Photograph to print black and white photograph contains a layer of either silver bromide (AgBr) or Silver Chloride (AgCl).

When light is passed through the negative (film) of photograph on the photographic paper containing a layer of either silver bromide or silver chloride, then it decomposes and gives silver metals which is grey in colour. And using this process photograph gets printed on the photographic paper.

Although, now-a-days black and white photography became the matter of history. Although, using this method black and white photograph can be printed.