Question

Sodium thiosulphate is used to remove the unexposed $AgBr$ from photographic films by forming a complex. In this complex of silver, the coordination number of silver is:

• A. 2
• B. 4
• C. 6
• D. 8

Answer 1

The correct option is B 4

Silver bromide reacts with sodium thiosulphate solution to form sodium argentothiosulphate $N{a}_3\left[Ag\right(S_2{O}_3{)}_2]$.
In this complex, the coordination number of silver is 4.
$AgBr\left(s\right)+2N{a}_2{S}_2{O}_3\to N{a}_3\left[Ag\right(S_2{O}_3{)}_2]$