Variable Oxidation States Flashcards
What is the max oxidation state and what has that?
What do metal ions with oxidation state of M3+ exist as?
What are lower oxidation states?
+7 and Mn
Covalently bonded to very high electronegative element
Reducing
Potassium Manganate and potassium dichromate what are they?
Equation of Cr2O72- to Cr3+
Good oxidising agents
Cr2O72-+14H++6e->2Cr3++7H2O
Potassium Manganate What is required? Why? When is colour seen? What is the end point? What kind of condition does it need? Why? What can the acid not be? Why?
Why not HCl?
Why not CH3COOH?
Why not HNO3?
Why not conc H2SO4?
What is used?
Indicator Mn is colourless When xs dark purple MnO4- added Pink Acidic needs xs H+ Reducing agent be it could be oxidised
Would be oxidised
Too weak
Oxidising agent
Oxidising agent
Dilute H2SO4
Potassium Dichromate What's the indicator? What does it go from? What acids can be used? Why can HCl?
Diphenylamminesuphonate
Colourless to purple
HCl or H2SO4
Dichromate can’t hydrolyse
Chromium reduced using zinc What does it happen in? What does Cr2O42- go to? Equation? What does the colour depend on? What's the colour in acidic and the colour in alkaline? What colour is Cr3+? What colour is Cr2+? What condition does Cr2+ require? How does it get this these conditions?
Sequence Cr2O72- 2CrO72-+2H+ >Cr2O72-+H2O Ph Yellow to orange Green Blue No air Hydrogen produced excludes air
Alkaline What happens in low oxidation states? What must conditions be to store Fe2+ without it oxidising? How do you prepare metal complex?(2) Reaction of [Cr(OH)6]3- with H2O2 How is [Co(H2O)4(OH)2] oxidised?
Oxidised higher Acidic Add alkaline NaOH add oxidising agent eg H2O2 2[Cr(OH)6]3-+H2O2>Cr2O42-+2OH-+8H2O Shaken in air
What is cobalt rapidly excited to?
Dark brown hexamine cobalt
What are all except Sc?
Why does stability of M2+ increase across first row?
+2
Nuclear charge increases,remaining electron held more tightly with no increase in shielding
