8 7. 1 Electrolyte and electrolytic solution Out-class reading Levine, pp. 294-310 Section 10.6 solutions of electrolytes Section 10.9 ionic association pp512515 Section 16.6 electrical conductivity of electrolyte solutions
§7.1 Electrolyte and electrolytic solution Out-class reading: Levine, pp. 294-310 Section 10.6 solutions of electrolytes Section 10.9 ionic association pp. 512-515 Section 16.6 electrical conductivity of electrolyte solutions
87.1 Electrolyte and electrolytic solution Contents of solution chemistry Main contents (1) non-electrolytic solution: Colligative )Electrolyte: origin of the concept 2)Existence of ions in solution roperty and activity 3)Ion-dipole interaction--Hydration theory (2)electrolytic solution: conductivity and 4) Interionic interaction mean activity 5)Motion under electric field 6)Conducting mechanism (3 Solution reaction: kinetics and 7)Faradays law and its application mechanism
Main contents: 1) Electrolyte: origin of the concept 2) Existence of ions in solution 3) Ion-dipole interaction--Hydration theory 4) Interionic interaction 5) Motion under electric field 6) Conducting mechanism 7) Faraday’s law and its application Contents of solution chemistry (1) non-electrolytic solution: Colligative Property and activity (2) electrolytic solution: conductivity and mean activity (3) Solution reaction: kinetics and mechanism §7.1 Electrolyte and electrolytic solution
87.1 Electrolyte and electrolytic solution 1)Definition of electrolyte Progress of the definition An electrolyte is a substance that when dissolved in solvent, produces a (1)molten salt; solution that will conduct electricity. (2)solid-state electrolyte: Al,O3, ZrO2, PEO and Nafion: (3)Room-temperature ionic liquids (RTIL)
An electrolyte is a substance that, when dissolved in solvent, produces a solution that will conduct electricity. 1) Definition of electrolyte Progress of the definition: (1) molten salt; (2) solid-state electrolyte: Al2O3 , ZrO2 , PEO and Nafion; (3) Room-temperature ionic liquids (RTIL). §7.1 Electrolyte and electrolytic solution
87.1 Electrolyte and electrolytic solution 2)Dissociation of substance In 1885, vant Hoff published his quantitative research on the colligative properties of solution For sucrose, the osmotic pressure (r can be expressed as: 丌=cRT But for some other kind of solvates such as Nacl the osmotic pressure had to be modified as: Jacobus henricus van 't Hoff IcRT 1901 Noble prize i, vant Hoff factor, is larger than 1. 1852/0830~1911/03/01 Discover the laws of chemical dynamic and the osmotic pressure in solutions In the paper written in Achieves Neerlandaises(1885)and Transactions of the Swedish Academy (1886, vant Hoff showed analogy between gases and dilute solutions
In 1885, van’t Hoff published his quantitative research on the colligative properties of solution. For sucrose, the osmotic pressure () can be expressed as: = c R T But for some other kind of solvates such as NaCl, the osmotic pressure had to be modified as: = i c R T i , van’t Hoff factor, is larger than 1. 2) Dissociation of substance In the paper written in Achieves Neerlandaises (1885) and Transactions of the Swedish. Academy (1886), van't Hoff showed analogy between gases and dilute solutions. §7.1 Electrolyte and electrolytic solution
87.1 Electrolyte and electrolytic solution 2)Dissociation of substance In 1885, followed L Equilibre chimique dans les systemes gazeux ou dissous a l'Etat dilue(chemical equilibria in gaseous systems or strongly diluted solutions ) which dealt with this theory of dilute solutions. He demonstrated that the "osmotic pressurein solutions which are sufficiently dilute is proportionate to the concentration and the absolute temperature so that this pressure can be represented by a formula which only deviates from the formula for gas pressure by a coefficient i. He also determined the value of i by various methods, for example by means of the vapour pressure and raoult s results on the lowering of the freezing point. Thus van't Hoff was able to prove that thermodynamic laws are not only valid for gases, but also for dilute solutions. His pressure laws, given general validity by the electrolytic dissociation theory of Arrhenius(1884-1887-the first foreigner who came to work with him in Amsterdam(1888)-are considered the most comprehensive and important in the realm of natural sciences http://www.nobelprize.or izes/chemistry/laureates/1901/hoff-bio html
In 1885, followed L'Équilibre chimique dans les Systèmes gazeux ou dissous à I'État dilué(Chemical equilibria in gaseous systems or strongly diluted solutions), which dealt with this theory of dilute solutions. He demonstrated that the "osmotic pressure" in solutions which are sufficiently dilute is proportionate to the concentration and the absolute temperature so that this pressure can be represented by a formula which only deviates from the formula for gas pressure by a coefficient i. He also determined the value of i by various methods, for example by means of the vapour pressure and Raoult's results on the lowering of the freezing point. Thus van 't Hoff was able to prove that thermodynamic laws are not only valid for gases, but also for dilute solutions. His pressure laws, given general validity by the electrolytic dissociation theory of Arrhenius (1884-1887) - the first foreigner who came to work with him in Amsterdam (1888) - are considered the most comprehensive and important in the realm of natural sciences. http://www.nobelprize.org/nobel_prizes/chemistry/laureates/1901/hoff-bio.html 2) Dissociation of substance §7.1 Electrolyte and electrolytic solution
87.1 Electrolyte and electrolytic solution 3) Dissociation theory for weak electrolytes In 1887, Svant A. Arrhenius postulated that, when dissolved in adequate solvent, some substances can split into smaller particles, the process was termed as dissociation AB A++ B molecule cation anion 匚 SvanteArrhenius positive ion negative ion 1903 Noble prize Sweden The charged chemical species are named as ions 1859/0219~1927/1002 for his great contribution to solution and the process is termed as ionization chemistry
In 1887, Svant A. Arrhenius postulated that, when dissolved in adequate solvent, some substances can split into smaller particles, the process was termed as dissociation. AB ⎯→ A+ + B – molecule cation anion positive ion negative ion The charged chemical species are named as ions and the process is termed as ionization. + − ⎯⎯→ + − 3) Dissociation theory for weak electrolytes §7.1 Electrolyte and electrolytic solution
87.1 Electrolyte and electrolytic solution New definitions. Weak/strong electrolyte? Ion, cation, anion; True/ potential electrolyte? Dissociation ionization Is sulfuric acid a strong or a weak Theory of Electrolytic Dissociation electrolyte Acid-base theory Is Nacl a strong electrolyte?
New definitions: Ion, cation, anion; Dissociation, ionization Theory of Electrolytic Dissociation Acid-base theory Cf. Levine p.295 Is sulfuric acid a strong or a weak electrolyte? Is NaCl a strong electrolyte? §7.1 Electrolyte and electrolytic solution Weak / strong electrolyte? True / potential electrolyte?
87.1 Electrolyte and electrolytic solution 2. Ions in solution In what state do ions exist in solution? Solvated(hydrated) ion Primary hydration shell 6+···6- secondary hydration shell Disordered layer Bulk solution ovation shells
Solvated (hydrated) ion 2. Ions in solution In what state do ions exist in solution? ion Primary hydration shell secondary hydration shell Disordered layer Bulk solution Solvation shells §7.1 Electrolyte and electrolytic solution
87.1 Electrolyte and electrolytic solution Hydration of ion The water molecules in the hydration sphere and bulk water have different properties which can be distinguished by spectroscopic techniques such as nuclear magnetic resonance(NMR), infrared spectroscopy (R), and Xrd etc Coordination number. Lit:4,K+:6 Coordination number? Primary solvation shell 4-9. 6 is the most common number Secondary solvation shell 6-8. for A+ and Cr3+: 10-20
Hydration of ion Coordination number: Li+ : 4, K+ : 6 Primary solvation shell: 4-9, 6 is the most common number Secondary solvation shell: 6-8, for Al3+ and Cr3+: 10-20 The water molecules in the hydration sphere and bulk water have different properties which can be distinguished by spectroscopic techniques such as nuclear magnetic resonance (NMR), infrared spectroscopy (IR), and XRD etc. Coordination number? §7.1 Electrolyte and electrolytic solution
87.1 Electrolyte and electrolytic solution 3. Hydration Theory /Solvation Theory Why does Nacl only melt at higher temperature, but dissolve in water at room temperature Na(g)+cr(g 1948. Robinson and Storks hydration energy: 784 k mol-l NaOM)+H,Ow) 788784 Na*(aq)+ CF(ag)
3. Hydration Theory / Solvation Theory H / kJ mol -1 4 NaCl(s) Na+ (aq) + Cl− (aq) Na+ (g) + Cl− (g) 788 784 hydration energy: 784 kJ mol-1 Why does NaCl only melt at higher temperature, but dissolve in water at room temperature? 1948, Robinson and Storks §7.1 Electrolyte and electrolytic solution
