Reactions of Ions in Aqueous Solutions Flashcards
what is a metal aqua complex
it is a complex that is formed when a transition metal compound is added to water
what affects how acidic a metal aqua complex is and why are they acidic
the charge of the complex affects how how acidic the metal complex is. metal aqua ions are acidic when in solution
what is the reaction when [Fe(H2O)6]2+ reacts with water and what is this reaction called
[Fe(H2O)6]^2+ + H2O = [Fe(H2O)5(OH)]^+ + H3O+
the hydroxonium ion is what makes the solution acidic.
this is a hydrolysis reaction
what happens when you react [Fe(H2O)6]^3+ and water and what is this reaction called
[Fe(H2O)6]^3+ + H2O = [Fe(H2O)5(OH)]^2+ + H3O+
this is also a hydrolysis reaction
what is the difference between the hydrolysis of a 2+ complex and a 3+ complex
- 2+ complex ions dissociate weakly so they are not very acidic
- 3+ complex ions dissociate more readily than 2+ complexes and are more acidic.
why are 3+ complexes more acidic than 2+ complexes and why does this allow the complex to dissociate to form a more acidic solution
this is because 3+ metal ions have a higher charge density than 2+ metal ions. this is because they have a larger charge and are small.
- this means that the 3+ metal ions are more polarising than the 2+ metal ions. this means that they attract the O-H bond in the ligands more strongly, this weakens the bond. this means that the H+ ion is more likely to be lost which means the 3+ metal ions form a more acidic solution.
what is the further hydrolysis of metal aqua ions
it is the addition of more water to the metal aqua ion to more an insoluble metal hydroxide.
e.g. metal(H2O)3(OH)3 (s)
the complex no longer has a charge.
why is an insoluble metal hydroxide formed when the metal aqua ion is further hydrolysised
this is because a neutral complex is formed which is solid which forms a precipitate in solution.
what are the two general reactions for when a 2+ & 3+ metal aqua ions are further hydrolsised to form an insoluble metal hydroxide
[M(H2O)6]^2+ + 2H2O = M(H2O)4(OH)2 + 2H3O^+
[M(H2O)6]^3+ + 3H2O = M(H2O)3(OH)3 + 3H3O^+
how can you reverse the formation of the metal hydroxide formed from hydrolysis
add and acid (h+) and the precipitate will dissolve. this is only possible when the metal hydroxide is amphoteric e.g aluminium
what happens when you add a base (OH-) or and acid (H3O+) to aluminium hydroxide
Al(H2O)3(OH)3 + OH^- = [Al(H2O)2(OH)4]^- + H2O
Al(H2O)3(OH)3 + 3H3O^+ = [Al(H2O)6]^3+ + 3H2O
what does adding ammonia to a metal aqua ion do and what could happen when you add an excess of ammonia
adding ammonia to metal aqua ions form a metal hydroxide precipitate too.
sometimes when adding an excess of ammonia could lead to partial ligand subsitution.
what is the equilibrium equation for when ammoina is in solution
NH3 + H2O ⇌ NH4^+ + OH^-
what is the reaction for when and excess of ammonia to cu(H2O)4(OH)2
the ligands are displaced an a charge soluble complex is formed
Cu(H2O)4(OH)2 + 4NH3 = [Cu(NH3)4(H2O)2]^2+ + 2OH^- + 2H2O
what happens when you add sodium carbonate to 2+ metal aqua ions
it forms metal carbonate precipitates
what is the general formula for when you react a 2+ metal aqua ion with carbonate ions
[M(H2O)6]^2+ + CO3^2- ⇌ MCO3 + 6H2O
what is the general formula for when you react a 3+ metal aqua ion with carbonate ions and why does this occur
2[M(H2O)6]^3+ + 3CO3^2- ⇌ 2M(H2O)3(OH)3 + 3CO2 + 3H2O
- this is because 3+ metal ions are more acidic than 2+ and therfore ther is more H3O^+ ions in solution so the carbonate reacts with the H3O+ instead of displacing the water ligands.
what are the steps of test tube reactions that are used to identify an unknown metal ion solution
- add sample of unknown metal ion solution into 3 test tubes
- add sodium hydroxide drop by drop to test tube 1 and observe any changes. and then add more sodium hydroxide to see if an excess results in any further change
- add ammonia solution to test tube 2 drop by drop and observe any change. then add in excess to see if it results in a change
4.then add sodium carbonate drop by drop and record any change
what is a safety precaution that can be used when dealing with ammonia
ammonia gives off pungent fumes and should therefore be done in a fume cupboard
what happens when you add an excess of sodium hydroxide to aluminium hydroxide
the precipitate dissolves when in excess and this is because aluminium is amphoteric
what is the colour for :
[Cu(H2O)6]^2+
[Fe(H2O)6]^2+
[Fe(H2O)6]^3+
[Al(H2O)6]^3+
[Cu(H2O)6]^2+ = blue sol
[Fe(H2O)6]^2+ = green sol
[Fe(H2O)6]^3+ = yellow sol
[Al(H2O)6]^3+ = colourless sol
what is the colour change for adding HCL to :
[Cu(H2O)6]^2+
[Fe(H2O)6]^2+
[Fe(H2O)6]^3+
[Al(H2O)6]^3+
[Cu(H2O)6]^2+ = gr -yel sol
[Fe(H2O)6]^2+ = bl - yel sol
[Fe(H2O)6]^3+ = or - yel sol
[Al(H2O)6]^3+ = remains colourless
what is the colour change when ammonia (NH3) is added to:
[Cu(H2O)6]^2+
[Fe(H2O)6]^2+
[Fe(H2O)6]^3+
[Al(H2O)6]^3+
[Cu(H2O)6]^2+ = blue sol - pale blue precipitate ( in ex deep blue solution)
[Fe(H2O)6]^2+ = green sol - green precipitate
[Fe(H2O)6]^3+ = orange sol - brown precipitate
[Al(H2O)6]^3+ = colorless sol - white precipitate
what is the colour change when you add some OH- to:
[Cu(H2O)6]^2+
[Fe(H2O)6]^2+
[Fe(H2O)6]^3+
[Al(H2O)6]^3+
[Cu(H2O)6]^2+ = blue sol -
pale blue precipitate
[Fe(H2O)6]^2+ = green sol - green precipitate
[Fe(H2O)6]^3+ = orange sol - orange precipitate
[Al(H2O)6]^3+ = colorless sol - white precipitate
