Previously in Chem104: Titration review Buffers: little more Lewis acid/base reactions
description
Transcript of Previously in Chem104: Titration review Buffers: little more Lewis acid/base reactions
![Page 1: Previously in Chem104: Titration review Buffers: little more Lewis acid/base reactions](https://reader035.fdocuments.in/reader035/viewer/2022081506/56813e30550346895da8144d/html5/thumbnails/1.jpg)
Previously in Chem104:
•Titration review
•Buffers: little more
• Lewis acid/base reactions
• complex ions• solubility
• Solubility Product
Today in Chem104:
• Solubility Product• Ksp• Common Ion Effect• pH effect• Chelate Effect
• Examples
• Iron Bioavailability:•an example of asolubility problem for Life
![Page 2: Previously in Chem104: Titration review Buffers: little more Lewis acid/base reactions](https://reader035.fdocuments.in/reader035/viewer/2022081506/56813e30550346895da8144d/html5/thumbnails/2.jpg)
All ionic solids dissolve using Lewis A/B interactions
MX(s) + 6H2O [M(H2O)6]+ + X(aq)-
M+:OH2
e- acceptor :e- donorLewis Acid :Lewis Base
Mn+
H2O
H2O OH2
OH2
H2O
OH2
![Page 3: Previously in Chem104: Titration review Buffers: little more Lewis acid/base reactions](https://reader035.fdocuments.in/reader035/viewer/2022081506/56813e30550346895da8144d/html5/thumbnails/3.jpg)
All ionic solids dissolve using Lewis A/B interactions
AgCl(s) + 2H2O [Ag(H2O)2]+ + Cl-
Ksp = 1.8 x10-10 Ksp = [Ag+][Cl-] and [Ag+] = [Cl-] 1.8 x10-10 = [Ag+][Cl-] = x2
AgCl(s) Ag+ + Cl-Written simply:
This is typical expression for solubility equilibriumGiven by the Solubility Product Ksp
Very low solubility due to weak Lewis A/B interactions which does not compensate for large lattice energy
x = 1.3 x10-5 M = [Ag+] = [Cl-] This is the molar solubility of AgCl
![Page 4: Previously in Chem104: Titration review Buffers: little more Lewis acid/base reactions](https://reader035.fdocuments.in/reader035/viewer/2022081506/56813e30550346895da8144d/html5/thumbnails/4.jpg)
Ionic solids which completely dissolve are highly soluble and cannot be described with a Ksp
NaCl(s) + 6H2O [Na(H2O)6]+ + Cl-
Ionic solids which slightly dissolve are thosewhose solubility can be described with a Ksp
AgCl(s) Ag+ + Cl- Ksp = 1.8 x10-10
CaCO3(s) Ca2+ + CO32- Ksp = 3.4 x10-9
CaF2(s) Ca2+ + 2 F- Ksp = 5.3 x10-11
Ag2S(s) 2 Ag+ + S2- Ksp = 6.1 x10-51
![Page 5: Previously in Chem104: Titration review Buffers: little more Lewis acid/base reactions](https://reader035.fdocuments.in/reader035/viewer/2022081506/56813e30550346895da8144d/html5/thumbnails/5.jpg)
Solubility obeys
AgCl(s) Ag+ + Cl- + excess Cl-
Ksp = 1.8 x10-10 Solubility =1.3 x10-5 M = [Ag+] = [Cl-]
AgCl(s) Ag+ + Cl-
If more chloride is added the equilbirum shifts left,and Solubility Product Ksp requires less AgCl dissolves
Ksp = 1.8 x10-10 Solubility, [Ag+] <1.3 x10-5 M
What if more Cl- is added to this equilibrium?
![Page 6: Previously in Chem104: Titration review Buffers: little more Lewis acid/base reactions](https://reader035.fdocuments.in/reader035/viewer/2022081506/56813e30550346895da8144d/html5/thumbnails/6.jpg)
otherwise called The Common Ion Effect obeys
AgCl(s) Ag+ + Cl- + excess Cl-
Ksp = 1.8 x10-10 and Solubility =1.3 x10-5 M = [Ag+] = [Cl-]
For the dissolution of silver chloride, AgCl(s) Ag+ + Cl-
When additional chloride is added, Solubility Product Ksp requires less AgCl dissolves
Ksp = 1.8 x10-10 but
Solubility of silver ion is decreased, [Ag+] <1.3 x10-5 M because [Cl- ] >>1.3 x10-5 M
![Page 7: Previously in Chem104: Titration review Buffers: little more Lewis acid/base reactions](https://reader035.fdocuments.in/reader035/viewer/2022081506/56813e30550346895da8144d/html5/thumbnails/7.jpg)
Cleanliness is
next to Godliness
So controlling solubility can make you more holy?
Let’s see how…
![Page 8: Previously in Chem104: Titration review Buffers: little more Lewis acid/base reactions](https://reader035.fdocuments.in/reader035/viewer/2022081506/56813e30550346895da8144d/html5/thumbnails/8.jpg)
The pH Effect obeys
Ksp = 3.7 x10-9
Ca(CO3)(s) Ca2+ + CO32-
If pH is lowered by adding acetic acid,more CaCO3 dissolves
…. and cleans the teapot:
+ AH
HCO3-
H2CO3
+ AHH2O + CO2
+ AH
![Page 9: Previously in Chem104: Titration review Buffers: little more Lewis acid/base reactions](https://reader035.fdocuments.in/reader035/viewer/2022081506/56813e30550346895da8144d/html5/thumbnails/9.jpg)
The Chelate Effect obeys
Ksp = 3.7 x10-9
Ca(CO3)(s) Ca2+ + CO32-
If Ca2+ is removed by adding a ligand,
more CaCO3 dissolves
…. and also cleans the dishwasher:
+ citric acid
Ca(citrate)
COOHHOC
COOHHOO
-OCCO-
-OC
OH
O
O
OCa2+
![Page 10: Previously in Chem104: Titration review Buffers: little more Lewis acid/base reactions](https://reader035.fdocuments.in/reader035/viewer/2022081506/56813e30550346895da8144d/html5/thumbnails/10.jpg)
Making better (stronger) Lewis A/B interactionscan improve solubility and clean, too
We have seen:AgCl(s) + 2H2O [Ag(H2O)2]+ + Cl-
Ksp = 1.8 x10-10
AgCl can be completely dissolved!
Very low solubility due to weak Lewis A/B interactions which do not compensate for large lattice energy
But if ammonia is Lewis base:AgCl(s) + 2 NH3 [Ag(NH3)2]+ + Cl-
![Page 11: Previously in Chem104: Titration review Buffers: little more Lewis acid/base reactions](https://reader035.fdocuments.in/reader035/viewer/2022081506/56813e30550346895da8144d/html5/thumbnails/11.jpg)
Does Q have a role in Ksp problems? YES!!Possible outcomes for MX(s) <==> M+ + X-
1. Q Ksp
2. Q < Ksp
3. Q > Ksp
Reactants Products; all salt dissolved
Reactants & Products in equilibrium; Solution is Saturated
Products Reactants; solid precipitates
![Page 12: Previously in Chem104: Titration review Buffers: little more Lewis acid/base reactions](https://reader035.fdocuments.in/reader035/viewer/2022081506/56813e30550346895da8144d/html5/thumbnails/12.jpg)
![Page 13: Previously in Chem104: Titration review Buffers: little more Lewis acid/base reactions](https://reader035.fdocuments.in/reader035/viewer/2022081506/56813e30550346895da8144d/html5/thumbnails/13.jpg)
A Siderophore“iron carrier”
Iron(III) Siderophoreready for transport