Question

Solid silver bromide (AgBr) will disassociate slightly in water to produce Agand Br". AgBr(s) + Agfaq) + Brīaq) Ksp = 1.3 x 10-5 a. Calculate the equilibrium concentration of Ag+ if the solution if the solid AgBr is dissolved in pure water. Assume that the solution is behaving ideally (y = 1)

Answer 1

Answer to the problem . we have the following equilibrium, Agbr (s) Agilan + B5 (an) & I deal solution Agar (6) ~ Anglia, trans Hetividas solubility Products, a a La= aagt - Activity of Agtion dont = Activity of Brion We know, we above a-fe For ideal stution to fugatity Coeficient or activitg coefficiant- f 1 od 1 a= 0 taa eng x Canx ft . s ta - Cag. Con = Kep Ksp = 1:3x105 or 1.3x105 = sxs Let the solubility of Again () in a, s' = 1:3x165 Pure water is s. or s = 3.66x103 m .. Equilibrium concentration of Agt ie Cat = 3.60xio ºm

6 Non-ideal solution a=fc ft to So we have to determine activity Coefficiant e f. For this purpose we use Extended - Deby - Huckel equation; logf = – 0:51 x ZA x M A = fugacity as activity 1+ 3.3 **Axtu Coefficiant & Aat = 250pm = charge of the son's = 0. 250 nm Me solutions ionic Xar = 300 fom Strength. = 0.30 m nm XA = effective size of the ions in nm -0.51x1x Jon 1+ 3.3 x 0-25x701 M=0.1 =- 0.162 1624 = -0.129 1:26 fast = 100.129 - 0. 743 -0.51 x 12 x voin It 3.3 x 0.30x Jon -0.162 -= 1.32 -0.123 logkar = -0.123 frer = 100.123 _ 0.753 La = End Age x len pour 1083166 = 0.743x S x 0.753x5. 5² = 2.32x105 s = 4.83x10 M Cagt = 4.83 x15² m

C) In ideal solution the activity coefficient is unity and ionic strength is zero. So there is no effect on solubility.

But if we consider non ideal solution ionic strength plays important role on solubility. Upon increasing ionic strength activity coefficient decreases. At a particular temperature solubility product is constant. In order to keep solubility product constant solubility must have to be increased. That is why for non ideal solution concentration of Ag+ increases.