Question

Name the chemical used in black and white photography.

Answer 1

Hint:Photosensitive compounds are used in black and white photography and films which also changes color on decomposition by exposure of light. The chemical used is a chloride of a rare metal.

Complete answer:
Silver chloride which is a white crystalline solid is widely famous for its poor solubility in water. It forms a sparingly soluble solution with water. Chemical formula of silver chloride is $$\text{AgCl}$$ . It can be easily prepared by mixing silver nitrate with a salt containing chloride like sodium chloride. Its preparation reaction is as follow as:
$$\text{NaCl}+\text{AgN}{\text{O}}_3\to \text{AgCl}(\downarrow )+\text{NaN}{\text{O}}_3$$ .
Formation of silver chloride can be determined with the appearance of opaque white precipitates in this reaction. Silver chloride gets easily decomposed on exposure to light as it is a photosensitive compound. It loses its opaque white appearance on disintegration by light into elemental chlorine and metallic chlorine. This reaction is used in black and white photography and films. The photographic paper is prepared by using silver chloride. It is also used in photo chromic lenses. Other than black and white photography, it is widely used in manufacturing of stained glass, in bandages and wound healing products, as antimicrobial agent, etc.
Silver bromide which is a pale yellow colored and crystalline solid is also water insoluble salt. It forms a sparingly soluble solution with water. This compound is widely famous for its photosensitive property. It gets broken down into elemental bromine and metallic silver on exposure to light and loses its color. Along with silver chloride, it is being widely used in black and white photography and films.

Thus, the correct answers are silver chloride and silver bromide.

Note:
Silver chloride compound occurs naturally as a mineral chlorargyrite. On the other hand, the silver bromide is found naturally as the mineral bromargyrite.