Question

Which compound will precipitate first when solid silver nitrate (AgNO3) is slowly added to a solution containing 0.0120 M each of carbonate and chloride ions? Show your calculation to justify your answer. Assume the volume does not change appreciably when the silver nitrate is added.

Ksp values: AgCl, 1.6 X 10^-10 Ag2CO3, 8.1 X 10^-12

Answer 1

stion Precipitation occurs when kop of a solid is lesser than asp Clonic product). When ksp's Gesp ve ate equilibrium, propapritur tin Ag co 2 Agt t o ; Agco 24g + cg Osp = [ast] [w] ; resp = Agt) Ese] In asp we consider the molar conc. of ion at any instant other than equilibrium; In Ksp we consider the equilibrium molar conc. when Ksp <Qsp, the system will try to attain equilibrium, hence the equilibrium will shift to left. e precipitation starts. [Ag+] = Agng) - [co?-) = 0.0120M) [cī) = 0·0120 M · For Agcl, ksp = 1.681010; het is' be the solubility of Ard. Ag ds = [45) HCT), Ksp = [Agt] [ET] Agt) = Ksp = 1.6 X10'O_ [ci] O = 1.33x10m 0.0120 equilibrium conc. of Ast to start precipitation of Agc = 1.33 X168 m. For Aqce, Ksp = [agt? [eg:-) ; tsp = 8.1x10^2 [Ag+)2 = 8.1 x 1062 - 6.75x1610 0.0120 = 6:75x100 Agt] = 6.75*10'0)/2 = 2.60x105 m. equilibrium conc. of Agt to precipitate Agco = 2.60x105m. Agel will precipitate first as [Ag+] E 1-33 xlās me) is Tessex Ito an [Ast) required to precipitate Ag,c} (2.60 x105 )