美国材料化学课程 2-5.ppt

1、The Story of the Philosophers Stone, Hiding Two Nobel Medals from the Nazis and Dr. Kimels Ultimate Frisbee Team,Solubility and Solubility Products,Solubility: the amount of solid that dissolves 3 examples,Solubility and Solubility Products,b) The Common Ion Effect occurs when there is an excess of

2、one of the ions comprising the precipitate. Consider dissolution of AgCI in 10-3M CI- (aq). What is x? 8 x 10-14M,Solubility and Solubility Products,c) Diverse Ion Effect associated with the activity of the different ionic species (usually most pronounced for concentrations greater than 0.5 M). The

3、effect is due to changes in the activity as a function of ionic strength.,Solubility and Solubility Products,Solubility Product,Solubility and Solubility Products,* usually used since we assume concentration and activity are the same thing,Diverse Ion and Complexation,Consider AgI, ksp = 8.5 x 10-17

4、. The stoichiometric solubility is 9.2 x 10-9M. What if we add 0.3 M KSCN to a suspension of AgI at equilibrium? Two Reactions AgI Ag+ + I-ksp = 8.5 x 10-17 Ag+ +2SCN- Ag(SCN)2-b2 = 3.7 x 10-7 Ag+ forms very stable complex with SCN-,Diverse Ion and Complexation,All species are in equilibrium with on

5、e another Ag+ must be in equilibrium for both the dissolution and complex formation reactions Thus, we can use simultaneous equations to determine the impact of 0.3M KSCN on the solubility of AgI,Diverse Ion and Complexation,Overall solubility of AgI in the system containing KSCN Concentration of di

6、thiocyonate complex from the mass-action equation From the solubility product,Diverse Ion and Complexation,Assuming the solubility of AgI is small enough that the complex formation does not reduce the initial concentration of 0.3M KSCN, what is the solubility of AgI in this system?,Let s = solubilit

7、y and substitute,S = I-,Simplify and rearrange,Diverse Ion and Complexation,S = 1.68 x 10-5 M! Compare to 9.2 x 10-9 M 4 orders of magnitude INCREASE in solubility!,Wait, Theres More,Aqua Regia: “royal water” 1:3 of nitric acid to hydrochloric acid Dissolves noble metals (Au, Ag, Pt, etc.),Au (s) +

8、3 NO3- (aq) + 6 H+ (aq) Au3+ (aq) + 3 NO2 (g) + 3 H2O (l),Au3+ (aq) + 4 Cl- (aq) AuCl4- (aq),Wait, Theres More,When Germany invaded Denmark in World War II, the Hungarian chemist George de Hevesy dissolved the gold Nobel Prizes of Max von Laue and James Franck into aqua regia to prevent the Nazis fr

9、om stealing them. He placed the resulting solution on a shelf in his laboratory at the Niels Bohr Institute. After the war, he returned to find the solution undisturbed and precipitated the gold out of the acid. The Nobel Society then recast the Nobel Prizes using the original gold.,1943 chemistry,

10、for work on isotopes as tracers 1914 physics, discovery of the diffraction of x-rays by crystals 1925 physics, discovery of the laws governing the impact of an electron upon an atom (shared with Gustav Ludwig Hertz),de Hevesy,von Laue,Franck,Other “Tid-Bits”, 800 CE alchemist Jabir ibn Hayyan, credited with discovery of HCl and Aqua Regia Thus begins the jo