Aluminium

Question 1

Al shows a diagonal reaction to which element? and what is a diagonal relationship?

Answer 1

to Be. It is whne the first element in a group will behave chemically in a similar way to the second element of the next group rather than like its own group.

Question 2

high nuclear charge of Al

Answer 2

leads to strong polarising power (distort electron cloud) which leads to a high degree of covalent character, due to overlap of orbitals as a result of the distortion

Question 3

bonding with reasons in aluminium fluoride

Answer 3

F is very small and so not easily polarisable, no overlap so ionic

Question 4

bonding with reason of aluminium oxide

Answer 4

oxide is a very negative ion with high chrage and therefore not easily polarisable. no overlap therefore ionic

Question 5

bonding with reasonof AlX3

Answer 5

halide ions are large (on going down the group), easily polarisable. overlap of orbitasl results in intermediate bonding (ionic but with high degree of covaletn chracter, behaves like a covalent compound)

Question 6

give any info regarding hydrated Al ion, stabililty etc

Answer 6

Al ion is stabilized by co ordination of water molecules to from the complex hexaaquaaluminium III ion. the higgh ionization energy to form the Al3+ ion is largely alanced by the energy rleased when Al-OH bonds form. the co ordination of water molecules occurs through the donation of a lone pair from oxygen atoms.
(the high polarising power allows for Al to break water’s OH bond to form the ligands)

Question 7

similarities of Be and Al

Answer 7

both have high polarising power and same elctronegativity
form covalent metallic chlorides
their oxides and hydroxides are amphoteric

Question 8

what bonds are formed between the ligand and central metal ion

Answer 8

datve/co oridnate bond

Question 9

passivation of Al

Answer 9

the thickness of th oxide layer is increased using nitric acid

Question 10

prep of AlCl3

Answer 10

2Al+ 3X2 —> 2AlX3
anhydrous AlCl3:
Al heated in a stream of dry Cl2
chlorde formed exists as teh dimer Al2Cl6 and sublimes in the cold tube to produce a whiet anhydrous powder
Anhy CaCl2 is sued as a drying agent to amke sure that air compoing in contact with AlCL3 is free of water vapour

Question 11

hydrolysis of AlCl3 using large amounts of water

Answer 11

AlCl3 + H2O —> [Al(H2O6]3+ + Cl-
the hydrated ion then undergoes hydrolysis to form [Al(H2O)5(OH)]2+
for further hydrolysis a base is needed

Question 12

Al(OH)3 when dissolved in water?

Answer 12

[Al(H2O3(OH)3] white pp

Question 13

amphoteric nature of Al

Answer 13

Al+ HCl —> AlCl3 + H2

Al + 2OH- + H”O –> Al(OH)4- + H2

Question 14

amphoteric nature of Al(OH)3

Answer 14

AL(OH)3 + H+ —> Al3+ + H2O (OHs are removed from thecomplex ion and hexaaqua is left)

Al(OH)3+ OH- —> Al(OH)4-
protons are removed to from [Al(H2O)2(OH)4]-

Question 15

product upon addition of NaOH to Al(H2O)6]3+ and then excess NaOH added to that

Answer 15

[Al(H2O)6]3+ + H2O [Al(H2O)5(OH)]2+ + H3O+

[Al(H2O)5(OH)]2+ + H2O [Al(H2O)4(OH)2]+ + H3O+

[Al(H2O)4(OH)2]+ + OH_—-> [Al(H2O)3(OH)3] (s) + H2O

upon excess becomes colourless solution
[Al(H2O)3(OH)3] (s) + OH- [Al(H2O)2(OH)4]- + H2O

Question 16

dimerisation of AlCl3

Answer 16

AlCl3 Al2Cl6

the dimer persisits in the gas phase but it the temp is raised to 800 they break down to monomers again

Question 17

alum empirical formula

Answer 17

MiMiii(SO4)2.12H2O

i can be Na, K , Rb or NH4
iii can be Al, Fe or Cr

Question 18

heating hydrated AlCl3 until dehydration

Answer 18

[Al(H2O)6]Cl3   =[Al(H2O)5(OH)]Cl2 +HCl
product = [Al(H2O)4(OH)2]Cl +HCl
product = [Al(H2O)3(OH)3] +HCl
dehydration; product = Al(OH)3 +H2O
product = Al2O3 +H2O