Reactions of Ions in Aqueous Solution Flashcards
Are 2+ ions or 3+ ions more acidic in solution? why?
3+ ions are much more acidic
- 3+ ions are smaller and more highly charged, so have a higher charge density.
- They attract the electrons from the oxygen of the ligands much more strongly. This weakens the O-H bonds, so the complex readily releases a H+ ion into the solution, making it acidic.
Write an equation for the hydrolysis of a 3+ ion to
release a proton
[Fe(H2O)6]3+ (aq) ⇌ [Fe(H2O)5(OH)]2+ (aq) + H+ (aq)
What kind of acid is the complex ion acting as?
Why? [Fe(H2O)6]3+(aq) ⇌ [Fe(H2O)5(OH)]2+(aq) + H+(aq)
Bronsted-Lowry - donates a proton
Define a Lewis acid
Electron pair acceptor
Define a Lewis base
Electron pair donor
What is acting as the Lewis acid and what is acting as the Lewis base during the formation of complex ions?
The metal ion is acting at the Lewis acid and the ligands as Lewis bases
What happens to Fe2+ in aqueous solution?
Complex ion: [Fe(H2O)6]2+(aq)
Colour: green
What happens to Fe2+ when you add NaOH? (dropwise and excess)
Complex ion: [Fe(H2O)4(OH)2] (s)
Colour: green ppt, goes brown on standing in air
What happens to Fe2+ when you add NH3? (dropwise and excess)
Complex ion: [Fe(H2O)4(OH)2] (s)
Colour: green ppt, goes brown on standing in air
What happens to Fe2+ when you add Na2CO3?
Complex ion: FeCO3(s)
Colour: green ppt
Why does the green ppt go brown on standing in air in the reaction of Fe2+ with NH3?
Oxygen in the air oxidises Fe2+ to Fe3+, and [Fe(OH)3(H2O)3] is brown, so colour changes
What happens to Cu2+ in aqueous solution?
Complex ion: [Cu(H2O)6]2+
Colour: blue
What happens to Cu2+ when you add NaOH? (dropwise and excess)
Complex ion: [Cu(H2O)4(OH)2] (s)
Colour: blue ppt
What happens to Cu2+ when you add NH3? (dropwise)
Complex ion: [Cu(H2O)4(OH)2] (s)
Colour: blue ppt
What happens to Cu2+ when you add NH3? (excess)
Complex ion: [Cu(H2O)2(NH3)4]2+ (aq)
Colour: deep blue solution
What happens to Cu2+ when you add Na2CO3?
Complex ion: CuCO3
Colour: deep blue solution
What happens to Cu2+ when you add concentrated HCl?
Complex ion: [CuCl4]2- (aq)
Colour: pale green/yellow solution
What happens to Fe3+ in aqueous solution?
Complex ion: Fe(H2O)6]3+
Colour: Purple solution, may look yellow-brown due to [Fe(H2O)5(OH)]2+ (aq)
What happens to Fe3+ when you add NaOH? (dropwise and excess)
Complex ion: [Fe(H2O)3(OH)3] (s)
Colour: Brown ppt, may look orange-brown
What happens to Fe3+ when you add NH3? (dropwise and excess)
Complex ion: [Fe(H2O)3(OH)3] (s)
Colour: Brown ppt, may look orange-brown
What happens to Fe3+ when you add Na2CO3?
Complex ion: [Fe(H2O)3(OH)3] (s)
Colour: Brown ppt, may look orange-brown, effervesence
What happens to Al3+ in aqueous solution?
Complex ion: [Al(H2O)6]3+
Colour: Colourless solution
What happens to Al3+ when you add NaOH? (dropwise)
Complex ion: [Al(H2O)3(OH)3] (s)
Colour: White ppt
What happens to Al3+ when you add NaOH? (excess)
Complex ion: [Al(OH)4]- (aq)
Colour: Colourless solution
