Chapter 17, Problem 17.104QP

Crystals of AgBr can be removed from black-and-white photographic film by reacting the AgBr with sodium thiosulfate.

$\begin{array}{l}\text{AgBr}(s)+2{\text{S}}_2{\text{O}}_3{}^{2-}-(aq)\rightleftharpoons \\ {\text{[Ag}{(}_{{\text{S}}_2}]}^{3-}(aq)+{\text{Br}}^{-}(aq)\end{array}$

1. a What is the equilibrium constant for this dissolving process?
2. b In order to dissolve 2.5 g of AgBr in 1.0 L of solution, how many moles of Na₂S₂O₃ must be added?