Inorganic Reactions Flashcards
(52 cards)
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