2.6 Reactions of Ions in Aqueous Solution Flashcards
Are 2+ ions or 3+ ions more acidic in solution?
Why
3+ 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 this 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 ion
The metal ion is acting as the lewis acid and the ligands as lewis bases
What is the complex ion formed and colour for these tests for Fe2+
In aqueous solution
Add NaOH
Add NH3
Add Na2CO3
In aqueous solution - [Fe(H2O)6]2+(aq) - Green
Add NaOH - Fe(H2O)4(OH)2 - Green ppt, goes brown in air
Add NH3 - Fe(H2O)4(OH)2 - Green ppt, brown in air
Add Na2CO3 - FeCO3 - 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
What is the complex ion formed and colour for these tests for Cu2+
In aqueous solution
Add NaOH
Add NH3 (dropwise)
Add NH3 (excess)
Add Na2CO3
Add conc HCl
In aqueous solution - [Cu(H2O)6]2+ - Blue
Add NaOH - Cu(OH)2(H2O4) - Blue ppt
Add NH3(dropwise) - Cu(H2O)4(OH)2 - blue ppt
Add NH3(excess) - [Cu(H2O)2(NH3)4]2+(aq) - Deep blue solution
Add Na2CO3 - CuCO3 - blue green ppt
Add conc HCl - [CuCl4]2-(aq) - Pale green/yellow solution
What is the complex ion formed and colour for these tests for Fe3+
In aqueous solution
Add NaOH
Add NH3
Add Na2CO3
In aqueous solution - [Fe(H2O)6]3+ - purple solution, may look yellow-brown due to [Fe(H2O)5(OH)]2+(aq)
Add NaOH - Fe(H2O)3(OH)3 - Brown ppt may look orange-brown
Add NH3 - Fe(H2O)3(OH)3 - Brown ppt may look orange-brown
Add Na2CO3 - Fe(H2O)3(OH)3 - Brown ppt, may look orange-brown, effervesence
What is the complex ion formed and colour for these tests for Al3+
In aqueous solution
Add NaOH (dropwise)
Add NaOH (excess)
Add NH3
Add Na2CO3
In aqueous solution - [Al(H2O)6]3+ - colourless solution
Add NaOH(dropwise) - [Al(H2O)3(OH)3] (s) - White ppt
Add NaOH(excess) - [Al(OH)4]-(aq) - Colourless solution
Add NH3 - Al(H2O)3(OH)3 - White ppt
Add Na2CO3 - Al(H2O)3(OH)3 - White ppt, effervescence
What is the complex ion formed and colour for these tests for Co2+
In aqueous solution
Add NaOH
Add NH3
Add Na2CO3
Add HCl
In aqueous solution - [Co(H2O)6]2+ - Pink
Add NaOH - Co(H2O)4(OH)2 - Blue ppt
Add NH3 - [Co(NH3)6]2+(aq) - Pale brown solution
Add Na2CO3 - CoCO3(s) - Purple ppt
Add HCl - [CoCl4]2-(aq) - Blue solution