Question

How many grams of Na,s,o, are needed to dissolve 0.0607 moles of AgClin a 1.0L solution, if Kap for AgClis 1.8 x 10-10 and Ky for the complex ion is 4.7 x 1013) Report your answer with the correct number of significant figures. Provide your answer below:

Answer 1

When 0.0607moles of AgCl are dissolved in 1.0L solution , [Cl^-] = 0.0607/1.0 mol/L = 0.0607M

[Ag⁺] = Ksp/[Cl^-] = 1.8×10^-10/(0.0607) = 2.9654×10^-9 M

Ag⁺ + 2 S₂O₃^2- $\leftrightharpoons$ [Ag(S₂O₃)₂]^3- K_f = 4.7×10¹³

Since Kf is very large almost all of silver is present in complex form . Let x mol of sodium thiosulfate is needed to dissolve 0.0607mol of AgCl .

K_f = 4.7×10¹³ = 0.0607/((x-0.0607×2)² × 2.9654×10^-9)

(x-0.1214)² = 4.355×10^-7

x = 0.12206

Mass of sodium thiosulfate needed = number of moles × molar mass = 0.12206mol × 158.1077g/mol = 19.2986g

= 19 g. (Answer)