Question

Compound $N{a_2}{S_2}{O_3}.5{H_2}O$ is used in photography to:
A. reduce $AgBr$ to metallic $Ag$.
B. remove reduced $Ag$
C. remove undecomposed $AgBr$ as a soluble complex
D. convert metallic $Ag$ to silver salt.

Answer 1

We know that $AgBr$ plays an important role in the world of photography. It is photosensitive in nature. It helps in developing photographic images. It is mainly used in the black and white photography. $N{a_2}{S_2}{O_3}.5{H_2}O$ is also used in photography for an important reason. The name of the compound $N{a_2}{S_2}{O_3}.5{H_2}O$ is sodium thiosulphate.

Complete step by step solution:
As we know that $AgBr$ is used in black and white photography because it is photosensitive. When $AgBr$ is suspended in gelatin the grains of the $AgBr$ create a photographic emulsion. We also know that $N{a_2}{S_2}{O_3}.5{H_2}O$ is used in photography. $N{a_2}{S_2}{O_3}.5{H_2}O$ is used to fix the negative. The reaction between $N{a_2}{S_2}{O_3}.5{H_2}O$ and silver bromide can be written as $AgBr + 2N{a_2}{S_2}{O_3} \to N{a_3}[Ag{({S_2}{O_3})_2}] + NaBr$. We can see that in this reaction a complex compound is formed. Actually the undecomposed$AgBr$ is being removed as a soluble complex. So from the above explanation it is clear to us that

The correct answer of the given question is option- C.

Additional information:
Sodium thiosulphate or $N{a_2}{S_2}{O_3}.5{H_2}O$ is a white crystalline solid. It is odourless. The crystal structure of sodium thiosulphate is monoclinic. It is used in the medication of cyanide poisoning. It is also used to cure the side effects of the cancer medication known as cisplatin. Side effects of sodium thiosulphate is that it can cause muscle cramps, agitation, nausea , vomiting and pain in joints.

Note: Always remember that sodium thiosulphate is used to remove the undecomposed silver bromide as a soluble complex. Sodium thiosulphate has lots of medicinal values . The crystal structure of sodium thiosulphate is monoclinic. Remember the chemical equation $AgBr + 2N{a_2}{S_2}{O_3} \to N{a_3}[Ag{({S_2}{O_3})_2}] + NaBr$.