PROBLEM 16-135PROBLEM 16-135a. Write chemical equations for the dissolution of silver bromide and the reaction of silver ion and thiosulfate ion to form silver thiosulfate. Kf for silver thiosulfate is 5.2 x 1012. K = Kf x Ksp = 3.
Next, get the number of moles of AgBr present. All of it must be reacted. How much silver thiosulfate and bromine ions are therefore present? You should have concentrations of each of 7.4 x 10-4 M.
Write the equilibrium expression for the overall reaction. Apply the concentrations calculated above and let x = thiosulfate ion concentration. (You should have calculated K = 3 above) Solve for x to get the concentration of thiosulfate ion in solution at equilibrium.
Now, we need this much, plus 2 x (7.4 x 10-4) to account for the thiosulfate that we need to react.
So the total moles thiosulfate comes out to 1.9 x 10-3. Calculate the number of grams of sodium thiosulfate from this.
B. Find the molar mass of the hydrate. Multiply the mass
calculated above by the ratio of the molar mass of the hydrate to
the molar mass of the non-hydrate. Should equal 0.47 g.
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