CHAPTER II. POTENTIOMETRY AND REDOX TITRATIONS I ...

2. Chromous ChlorideCrCl 2 is a powerful reductant. Excess Cr 2+ is oxidized by atmospheric O 2 .3. Sulfur Dioxide and Hydrogen SulfideSO 2 and H 2 S are mild reducing agents that can be expelled by boiling in acidicsolution.4. A Column Packed with a Solid Reducing AgentJones Reductor – contains zinc coated with zinc amalgam.Zn 2+ + 2e = Zn(s) E° = −0.764 VZn is such a powerful reducing agent that the Jones reductor is not veryselective.Walden Reductor – filled with solid Ag and 1 M HCl.Walden reductor is more selective since reduction potential for Ag⎪AgCl(0.222 V) is high enough that species such as Cr 3+ and TiO 2+ are not reducedand therefore do not interfere in analysis of a metal such as Fe 3+ .Another selective reductor uses granular Cd metal. Passing NO −3Cd-filled column reduces NO − 3 to NO − 2 .through aiv/. Application of Standard OxidantsTABLE 2-21. “Skoog” Table 17-3 (p.366).a) Oxidation with Potassium PermanganateIn strongly acidic solution (pH ≤ 1),MnO − 4 + 8H + + 5e = Mn 2+ + 4H 2 Ovioletcolorless(permanganate) (manganous)In neutral or alkaline solution,E° = 1.507 V10