Inorganic Reactions Flashcards
How many water molecules are able to bond to one transition metal?
Six!
What is a Lewis Base?
An electron acceptor.
Gie an example of a Lewis acid-base reaction.
NH3(aq) + BF3(aq)—-> NH3BF3(aq)
What do Lewis acids and bases react to form?
Coordinate bonds.
Why is it that solutions containing metal-aqua ions are slightly acidic?
Because aqua-metal ions react with the water to form H3O+ ions - the metal-aqua ions behave as a weak acid.
Why is it that solutions containing metal-aqua 3+ ions are more acidic than solutions containing metal-aqua 2+ ions?
3+ ions have a high charge density than 2+ ions - they polarize the oxygen in the water more strongly. This weakens the OH bond in water, making it easier for it to release a proton.
Give the dissociation reaction of [Al(H2O)6]3+ in water.
[Al(H2O)6]3+ + H2O —-> [Al(H2O)5(OH)]2+ + H3O+
Give the overal hydrolysis reaction of [M(H2O)6]3+ to its precipitate.
[M(H2O)6]3+(aq) + 3H2O(l) —-> M(H2O)3(OH)3(s) + 3H3O+(aq)
How can a metal hydroxide be dissolved?
By the addition of the acid - this will turn the hydroxide into the highest oxidation state of the metal-aqua ion.
Which metal hydroxides dissolve in bases? Why and how do they do this?
Al(H2O)3(OH)3 and Cr(H2O)3(OH)3 are amphoteric and are able to react with a base by donating a proton to form a negative ion and water.
i.e. Al(H2O)3(OH)3(s)+ OH-(aq) —-> [Al(H2O)2(OH)4]-(aq) + H2O(l)
Why is it that adding ammonia to a solution makes it basic?
The ammonia reacts with the water to form ammonium and hydroxide ions.
How is it possible to form a non-soluble precipitate from a metal-aqua 2+ ion? Give an example reaction with [M(H2O)6]2+
By reacting a carbonate (i.e. Na2CO3)
[M(H2O)6]2+(aq) + CO32-(aq) <—-> MCO3(s) + 6H2O(l)
How is it possible to form a precipitate from a metal-aqua 3+ ion? What occurs in the reaction process for this that prevents the precipitate dissociating in acid?
By reacting the 3+ ions with a carbonate - the carbonate ions react with the H3O+, removing them from the solution and keeping the pH neutral.
What is the reaction between Cu (II) metal-aqua ions and NH3?
NH3 + H2O <—-> OH- + NH4+
[Cu(H2O)6]2+ + 2OH- —-> Cu(H2O)4(OH) + 2H2O
What is the reaction between Cr (III) metal-aqua ions and excess hydroxide ions?
[Cr(H2O)6]3++ 6OH-—-> [Cr(OH)6]3- + 6H2O
What happens to cobalt, copper and chromium metal-aqua ions when they are reacted with excess NH3?
The NH3 replaces the water ligands; all of them, apart from copper, which only gains 4 and keeps 2 H2O ligands.
What is the reaction between Aluminium aqua-metal ions and excess OH-?
[Al(H2O)6]3+ + 4OH- —-> [Al(H2O)2(OH)4]- + 4H2O
What is the reaction between Fe (III) and excess hydroxide ions?
The same as without excessive hydroxide ions - Fe (III) does not behave amphoterically.
[Fe(H2O)6]3+ + 3OH- —-> Fe(H2O)3(OH)3 + 3H2O
What is the reaction between cobalt (II) metal-aqua ions and Na2CO3?
[Co(H2O)6]2+ + CO32- —-> CoCO3 + 6H2O
What is the reaction between Cr (III) metal-aqua ions and Na2CO3?
[Cr(H2O)6]3+(aq) + 3H2O(l) —-> Cr(H2O)3(OH)3(s)
The carbonate removes the H3O+ ions formed.
CO32- + H+ —-> HCO3-
HCO3- + H+ —-> H2O + CO2
What is the reaction between copper (II) metal-aqua ions and excess NH3?
[Cu(H2O)6]2+(aq) + 4NH3(aq) —-> [Cu(NH3)4(H2O)2]2+(aq) + 4H2O(l)
Why is it that ligand substitution reactions usually entail a positive entropy change?
Because a substance of a higher entropy is more stable.
Why is it that ligand exchange reactions evolve very little heat?
Because the strength of the bonds formed and the strength of the bonds broken is very similar - the reaction absorbs as much energy as it expels.
What is the reaction between [Ni(NH3)6]2+ and 1,2-ethanediamine?
[Ni(NH3)6]2+ + 3NH2CH2CH2NH2 —-> [Ni(NH2CH2CH2NH2)3]2+ + 6NH3
Why is it that bidentate ligands usually substitute unidentate ligands?
When bidentate ligands substitute unidentate ligands, the entropy of the solution increases because the number of possible states the it has increased - there are more particles in the solution after than before. This process is known as chelation.
Why is it that EDTA4- replaces uni and bidentate ligands?
Because the complex is formed is of a higher entropy because EDTA4- is hexadentate and will release lots of particles by substituting multiple ligands - this further means that the solution formed (and hence complex) is also more stable.
Why is it that replacing multidentate ligands with unidentate ligands is difficult?
Because it would require an increase in the entropy of the system.
What is the reaction and colour change that occurs between Iron (II) in aqueous solution and non-excess ammonia? Why is this reaction able to occur?
[Fe(H2O)6]2+(aq) + 2NH3(aq) —-> Fe(H2O)4(OH)2(s) + 2NH4+(aq)
Pale green solution —-> Green p.p.t —-> Brown p.p.t.
The brown p.p.t. is Fe (III) hydroxide oxidized from Fe (II) hydroxide
This reaction actually involves the formation of hydroxide ions from the reaction between ammonia and water:
H2O + NH3 —-> NH4+ + OH-
What is the reaction between Iron (II) ions in aqueous solution with excess ammonia?
Same as for little -
[Fe(H2O)6]2+(aq) + 2NH3(aq) —-> Fe(H2O)4(OH)2(s) + 2NH4+(aq)
Fe(H2O)4(OH)2(s) —-> Fe(H2O)3(OH)3(s)
Green solution —-> Green p.p.t. —-> Brown p.p.t.
What is the reaction between aqueous Iron (II) ions and excess hydroxide ions?
The same as for little
Pale green solution —-> Green p.p.t. —-> Brown p.p.t.
What is the reaction between aqueous Iron (II) ions and sodium carbonate?
[Fe(H2O)6]2+(aq) + CO32-(aq) —-> FeCO3(aq) + 6H2O(l)
Pale green solution —-> Green p.p.t.
How is it possible to dissolve metal hydroxide precipitates? Why is it possible to dissolve them in this way?
By adding acid - it is possible to dissolve them this way because they actually exist in equilibrium with their solution states; adding acid shifts this equilibrium towards the solution.
What is the reaction between aqueous Cobalt (II) ions and sparing amounts of hydroxide? What is the colour change for this reaction?
[Co(H2O)6]2+(aq)+ 2OH-(aq) —-> Co(H2O)4(OH)2(s) + 2H2O(l)
Pink/colourless solution —-> Blue p.p.t.
What is the reaction between between excess hydroxide ions and aqueous cobalt (II) ions?
The same as for little
Colour change of pink/colourless solution —-> blue p.p.t.
What is the reaction between Co2+ ions in water and excess ammonia?
[Co(H2O)6]2+(aq) + 6NH3(aq)—-> [Co(NH3)6]2+(aq)+ 6H2O(l)
Pink/colourless solution —-> Straw coloured solution
Has an intermediary p.p.t. formed which is blue
The final solution also oxidizes to its 3+ state in oxygen, turning the solution dark brown
What is the reaction between [Co(H2O)6]2+ and sodium carbonate?
[Co(H2O)6]2+(aq) + CO32-(aq) —-> CoCO3(s) + 6H2O(l)
Pink/colourless solution —-> Purple p.p.t.
What is the reaction between [Co(H2O)6]2+ and conc. HCl?
[Co(H2O)6]2+(aq) + 4Cl-(aq) —-> [CoCl4]2-(aq)+ 6H2O(l)
Pink/colourless solution —-> Blue solution
What is the reaction between Cu (II) ions in aqueous solution and hydroxide ions?
[Cu(H2O)6]2+(aq) + 2OH-(aq) —-> Cu(H2O)4(OH)2(s) + 2H2O(l)
Pale blue solution —-> Pale blue p.p.t.
What is the reaction between Cu2+ ions in water and excess sodium hydroxide?
The same as for little.
Pale blue solution —-> Pale blue p.p.t.
What is the reaction between concentrated ammoniacal solution and Cu2+ ions in water?
[Cu(H2O)6]2+(aq) + 3NH3(aq) —-> [Cu(H2O)2(NH3)4]2+(aq) + 4H2O(l)
Pale blue solution —-> Dark blue solution
What is the reaction between Na2CO3 and Cu2+ ions in aqueous solution?
[Cu(H2O)6]2+(aq) + CO32-(aq) —-> CuCO3(s)+ 6H2O(l)
Pale blue solution —-> Blue-green p.p.t.
What is the reaction between aqueous Copper (II) and concentrated HCl acid?
[Cu(H2O)6]2+(aq)+ 4Cl-(aq) —-> [CuCl4]2-(aq) + 6H2O(l)
Pale blue solution —-> Yellow solution
What is the reaction between Fe (III) ions in aqueous solution and hydroxide ions?
[Fe(H2O)6]3+(aq) + 3OH-(aq)—-> Fe(H2O)3(OH)3(s) + 3H2O(l)
Yellow solution —-> Brown p.p.t.
What is the reaction between excess ammonia and Iron (III) ions?
Same as for litte;
Yellow p.p.t.—-> Brown p.p.t.
What is the reaction between Fe (III) ions in water and sodium carbonate ions? What is observed when this reaction occurs?
2[Fe(H2O)6]3+(aq) + 3CO3-(aq) —-> 2Fe(H2O)3(OH)3(s) + 3CO2(g) + 3H2O(l)
Bubbling
Yellow solution —-> Brown p.p.t.
Why is it that sodium carbonate only reacts with metal 2+ ions to form their carbonates and not metal 3+ ions?
2+ ions are not sufficiently acidic (they do not weaken their water ligands’ OH bonds enough) to liberate CO2 from the CO32- in sodium carbonate. When the carbonate reacts with a 3+ ion, it actually reacts with two protons produced from the hexaaquametal ion’s dissociation - this forms carbon dioxide and the metal precipitate is formed as a result of the loss of the protons.
What is the reaction between chromium (III) in aqueous solution with ammonia?
[Cr(H2O)6]3+(aq)+ 3NH3(aq) —-> Cr(H2O)3(OH)3(s) + 3NH4+(aq)
Ruby solution —-> Green p.p.t.
What is the reaction between [Cr(H2O)6]3+ and excess hydroxide ions?
[Cr(H2O)6]3+(aq) + 6OH-(aq) —-> [Cr(OH)6]3-(aq) + 6H2O(l)
Ruby solution —-> Green solution
What is the reaction between chromium (III) ions in aqueous solution and excess ammonia?
[Cr(H2O)6]3+(aq) + 6NH3(aq)—-> [Cr(NH3)6]3+(aq) + 6H2O(l)
Ruby solution —-> Purple solution
What is the reaction between chromium (III) ions in solution and sodium carbonate?
2[Cr(H2O)6]3+(aq) + 3CO32-(aq) —-> 2Cr(H2O)3(OH)3(s) + 3CO2(g) + 2H2O(l)
Ruby solution —-> Green p.p.t.
Bubbling
What is the reaction between aqueous aluminium ions and excess hydroxide ions?
[Al(H2O)6]3+(aq) + 4OH-(aq)—-> [Al(OH)4]-(aq) + 6H2O(l)
Both of these are colourless solutions
