Reactions of Ions in Aqueous Solutions
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What are metal-aqua complexes? What reaction do they undergo?
transition metal ion is added to water, and coordinate bonds form between them due to the lone pair on O Hydrolysis
What affects the acidity of metal-aqua complexes
charge on the transition metal ion hydroxonium ions form when water reacts with metal-aqua complexes
Which is more acidic: a 3+ metal-aqua complex ion or a 2+ metal-aqua complex ion? Why?
3+ metal-aqua complex ion -have a higher charge density (high charge and small size) -hence more polarising (attract electrons in the O-H bond more strongly) -weakens bond -more likely that H+ is released
What happens during hydrolysis and further hydrolysis of metal-aqua complexes?
Hydrolysis: -water is added to the metal-aqua complex -lone pair on O of the added water is attracted to the H on the water ligand -breaks the O-H bond, forming H3O+ ions Further hydrolysis: -an equilibrium is established -more OH- are added, which react with H3O+ -equilibrium shifts to the right -continues until insoluble metal hydroxides form (neutral precipitate))
Define amphoteric
when metal hydroxides can act as a base or an acid can be reversed by adding H+ to the metal hydroxide complex it will dissolve
What forms when ammonia reacts with metal-aqua complexes? What happens when excess ammonia is added?
Metal hydroxides Ligand substitution
What forms when sodium carbonate is added to metal-aqua complexes?
Metal carbonates precipitates
State the colour of [Fe(H2O6)]2+ (aq)
green solution
State the colour of [Cu(H2O6)]2+ (aq)
blue solution
State the colour of [Fe(H2O6)]3+ (aq)
purple solution may look ellow-brown due to some [Fe(H2O)5(OH)]2+ (aq)
State the colour of [Al(H2O6)]3+ (aq)
colourless solution
State the observation of [Fe(H2O6)]2+ reacting with NaOH that is added dropwise
green precipitate goes brown on standing in air
State the observation of [Cu(H2O6)]2+reacting with NaOH that is added dropwise
blue precipitate
State the observation of [Fe(H2O6)]3+ reacting with NaOH that is added dropwise
brown precipitate may look orange-brown
State the observation of [Al(H2O6)]3+ reacting with NaOH that is added dropwise
white precipitate
State the observation of [Fe(H2O6)]2+ reacting with excess NaOH
no further visible change
State the observation of [Cu(H2O6)]2+reacting with excess NaOH
no further visible change
State the observation of [Fe(H2O6)]3+ reacting with excess NaOH
no further visible change
State the observation of [Al(H2O6)]3+ reacting with excess NaOH
[Al(OH4)]- (aq) forms colourless solution