aqueous ions

Question 1

how are metal aqua complexes formed?

Answer 1

when we add a transitional metal compound to water
generaly 6 water molecules form coordinate bonds with the metal ion
lone pair on the oxygen allows this to form

Question 2

how are metal aqua ions acidic when is solution?

Answer 2

e.g [Fe(H2O)6]2+ + H2O⇌ [Fe(H2O)5(OH)]+ + H3O+
H3O+ produced means it acidic
the reaction is called hydrolysis

Question 3

how does charge effect metal aqua ions acidity

Answer 3

If their is higher charge density the ions are more polarising.They attract OH bond in the ligands more strongly.This weakens the bond between OH making it more likely H+ will be released

Question 4

what is further hydrolysis of metal aqua ions?

Answer 4

metal aqua ions can be hydrolysed several times until using OH- until they make insolouble metal hydroxides (solid)

[M(H2O)6]2+ + H2O ⇌ [M(H2O)5(OH-)]+ + H3O+
M(H2O)5(OH-)]+ + H2O ⇌ [M(H2O)4(OH-2) + H3O+

Question 5

what is amphoteric?

Answer 5

can act as base and acid

Question 6

how is aluminium hydroxide amphoteric ?

Answer 6

adding H+ (acid) to Al(H2O)3(OH)3 (solid) makes it acts as bronstead lowry base as it accepts it from the H3O+
Al(H2O)3(OH)3 + H3O+ -> [Al(H2O6)]3+ 3H2O
It can also act as a bronstead lowry acid as it can donate H+ to the
Al(H2O)3(OH)3 + OH- -> [Al(H2O2(OH)4)]- + H2O

Question 7

what is the effect of ammonia on metal aqua ions?

Answer 7

ammonia exists in the equilibrium
NH3 + H2O ⇌ NH4+ + OH-
in low amounts of NH3 the metal aqua ions produce the same metal hydroxides formed when adding a base
in excess amounts their is partial ligand substituion
e.g Cu(OH)2(H2O)4 + 4HN3 ⇌ [Cu(NH3)4(H2O)2]2+ + 2OH- + 2H2O

Question 8

what is the effect of metal carbonate on 2+ metal aqua ions and 3+ metal aqua ions

Answer 8

at 2+
metal ions react with carbonates to form an insolouble metal carbonate
their is a complete substitution of water ligands
at 3+
it is more acidic as there is a lot H3O+ so the carbonate react with this instead
no carbonate formed
2[M(H2O)6]3+ + 3CO2- ⇌ 2[M(OH3)3(H2O)3] + 3CO2 + 3H2O

Question 9

how can you distinguish between metal ions(Fe2+,Cu2+,Al3+,Fe3+) using sodium hydroxide, ammonia and sodium carbonate

Answer 9

1) Add sample of the unknwown metal ion solution in three testtubes
2) Add NaOh drop by drop to test tube 1 observe any changes
3) repeat with ammonia solution in test tube 2
4) repeat with sodium carbonate in test tube 3

For NaOH only Al3+ is the only one that forms precipitate and then dissolves
for ammonia Cu2+ is the only that forms precipitate and then dissolves(dark blue)
for sodium carbonate Al3+,Fe3+ form precipitate and CO2
Fe2+ and Cu2+ only form precipitate