Question

Which compound is used in photography?

• A. $N{a}_{2}S{O}_5$
• B. $N{a}_2{S}_2{O}_8$
• C. $N{a}_2{S}_2{O}_6$
• D. $N{a}_2{S}_2{O}_3$

Answer 1

Answer: (D)

In photography hypo is used to dissolved unaffected $AgBr$
The photographic plate is coated with the thin layer of an emulsion of silver bromide dispersed in gelatin. Hypo or sodium thiosulphate $(N{a}_2{S}_2{O}_3)$ is used in the fixing of image. It dissolves unaffected AgBr but leaves metallic silver unchanged
$\underset{\text{Hypo}}{2N{a}_2{S}_2{O}_3}+AgBr\to \underset{\text{Soluble}}{N{a}_3\left[Ag{\left(S_2{O}_3\right)}_2\right]}+NaBr$