Reactions of ions in aqueous solution Flashcards
(45 cards)
What metals form 2+ complexes
Fe
Cu
What metals form 3+ complexes
Fe
Al
Why are 3+ complexes more acidic than 2+ ones
The electrons in the O-H bonds are further away from the hydrogens in 3+ ions.
This makes the hydrogen atoms in the ligand water molecules have a greater positive charge, making them more attracted to water molecules in the solution.
As a result, they are more readily lost, making 3+ ions more acidic.
Why is aluminium special
It is amphoteric so its hydroxides dissolve in acid and bases
Why is
[Cu(H2O)6]2+ + H2O —> [Cu(H2O)5(OH)]+ + H3O+
less acidic than
[Fe(H2O)6]3+ + H2O —> [Fe(H2O)5(OH)]2+ + H3O+
The equilibrium of the Fe reaction is further to the right so more hydronium ions produces
What is the end point for most metal complexes
M(H2O)(OH)2 - this is now neutral so no ppt will form
What is important to remember about
[Cu(H2O)6]2+ + 2OH- —> Cu(H2O)4(OH)- + 2H2O
What type of reaction is it?
The H+ are being lost from the water. It isn’t ligand substitution
It is an acid-base reaction
What are the 2 reactions that take place when ammonia is added to [Cu(H2O)6]2+
What types are the reactions
[Cu(H2O)6]2+ + 2NH3 —> Cu(H2O)4(OH)2 + 2NH4+
Cu(H2O)4(OH)2 + 4NH3 —> [Cu(NH3)4(H2O)2]2+ + 2H2O + 2OH-
1st = acid-base
2nd = ligand substitution
What is the reaction that takes place between a carbonate ion and [Cu(H2O)6]2+
[Cu(H2O)6]2+ + CO3 2- —> CuCO3 + 6H2O
What is the reaction that takes place between a carbonate ion and [Cu(H2O)6]3+
2[Cu(H2O)6]3+ + 3CO3 2- —> 2Cu(OH)3(H2O)3 + 3H2O + 3CO2
Why do M3+ ions form CO2 when reacting with a carbonate
Their high charge density makes it too acidic to from carbonate ions so CO2 is made instead
What is the reaction between [Cu(H2O)6]2+ and Cl-
[Cu(H2O)6]2+ + 4Cl- —> [CuCl4]2- + 6H2O
Why do ligands replace water ligands
Bonds between new ligand and metal ion is stronger.
New ligand is present in very high conc.
An increase in entropy
What are all of the equations of [Al(H2O)6]3+ reacting with OH-
[Al(H2O)6]3+ + OH- —> [Al(H2O)5(OH)]2+ + H2O
[Al(H2O)5(OH)]2+ + OH- —> [Al(H2O)4(OH)2]+ + H2O
[Al(H2O)4(OH)2]+ + OH- —> Al(H2O)3(OH)3 + H2O
Al(H2O)3(OH)3 + OH- —> [Al(H2O)2(OH)4]- + H2O
[Al(H2O)2(OH)4]- + OH- —> [Al(H2O)(OH)5]2- + H2O
[Al(H2O)(OH)5]2- + OH- —> [Al(OH)6]3- + H2O
Give 2 equations to show aluminium is amphoteric
Al(H2O)3(OH)3 + 3H+ —> [Al(H2O)6]3+
Al(H2O)3(OH)3 + 3OH- —> [Al(OH)6]3-
What is the formula for the iron (II) aqueous ion
What colour will the solution be
[Fe(H2O)6]2+
Green solution
What is produces when an iron (II) aqueous ion reacts with NaOH
Fe(H2O)4(OH)2
Green ppt goes brown when standing in air
What is produces when an iron (II) aqueous ion reacts with an excess of NaOH
No further change
What is produced when an iron (II) aqueous ion reacts with NH3
Fe(H2O)4(OH)2
Green ppt goes brown when standing in air
What is produces when an iron (II) aqueous ion reacts with an excess of NH3
No further change
What is produced when an iron (II) aqueous ion reacts with Na2CO3
FeCO3
Green ppt
What is the formula for the copper (II) aqueous ion
What colour will the solution be
[Cu(H2O)6]2+
Blue solution
What is produces when a copper (II) aqueous ion reacts with NaOH
Cu(H2O)4(OH)2
Blue ppt
What is produced when a copper (II) aqueous ion reacts with an excess of NaOH
No further change
Remains Cu(H2O)4(OH) with blue precipitate
