transition metals

Question 1

transition element

Answer 1

a d block element that forms one or more stable ions with an incomplete d sub shell

Question 2

why do transition elements have variable oxidation states

Answer 2

variable oxidation= because the energy of the 3d and 4s orbitals are similar. There isn’t a huge increase in energy to remove a thrid electron than second or first
smaller difference in IE

Question 3

ligand

Answer 3

species with one or more lone pairs of electrons that form dative covalent bonds to a central transition element atom or ion

Question 4

complex ion

Answer 4

central transition metal ion surrounded by ligands, bonded to the central ion by dative/coordiate covalent bonds

Question 5

why from complex ions

Answer 5

ions have empty d orbitals available for lone pairs of electron
“energetically accessible and can form dative bonds with ligands”

Question 6

why behave as catalysts

Answer 6

have more than one stable oxidation state. can gain or lose electrons from going to one oxidation state to another. (oxidising or reducing agents)
“energetically accessible and can form dative bonds with ligands”

Question 7

why form coloured ions

Answer 7

have unfilled d orbitals, cause electrons to absorb energy and jump to higher energy levels. this light not absorbed is reflected and is what we perceive as colour.

Question 8

Copper sulfate + sodium hydroxide

Answer 8

[Cu(H2O)6]2+ + 2OH- –> Cu(OH-)2(H2O)4(s) + 2H2O

Question 9

NH3 to copper blue ppt

Answer 9

Cu(OH-)2(H2O)4(s) + 4NH3 –> Cu(NH3)4(H2O)2(aq)2+ + 2H2O + 2OH-
deep blue solution from pale blue ppt

Question 10

copper sulfate?? + hydrochloric acid

Answer 10

[Cu(H2O)6]2+ + 4Cl- –> Cu(Cl-)4(aq)2- + 6H2O

blue + yellow = green solution

Question 11

cobalt sulfate + sodium hyrdoxide

Answer 11

[Co(H2O)6]2+ + 2OH- –> Co(OH-)2(H2O)4(s) + 2H2O
pink solution to blue ppt
turns red when warmed if the alkali is in excess

Question 12

cobalt sulfate + conc NH3

Answer 12

[Co(H2O)6]2+ + 6NH3 –> Co(NH3)6(aq)2+ + 6H2O

pink solution to brown solution

Question 13

cobalt sulfate + conc hydrochloric acid

Answer 13

[Co(H2O)6]2+ + 4Cl- –> Co(Cl-)4(aq)2- + 6H2O

pink to blue solution

Question 14

Cobalt sulfate with cl-

Answer 14

tetrahedral

Question 15

Cobalt sulfate with scn-

Answer 15

tetrahedral

Question 16

Cobalt sulfate with oh-

Answer 16

tetrahedral

Question 17

degenerative orbitals

Answer 17

there are 5 d orbitals in an isolated transition element atom or ion in the same energy level

Question 18

non degenerative orbitals

Answer 18

the 5 d orbitals split after ligands bond and are in different energy levels

Question 19

octahedral complexes, two higher and three lower d orbita

Answer 19

3dx2 - y2 and 3dz2 have lobes on the axis where the ligands attached or approaching
therefore the electrons in these orbitals are closer to bonding electrons so more repulsion and higher energy level

Question 20

tetrahedral complexes, three higher and two lower d orbitals

Answer 20

3dx2 - y2 and 3dz2 have lobes between the axis where the ligands attached or approaching
therefore the electrons in these orbitals are further from bonding electrons so less repulsion and lower energy level

Question 21

explain why transition elements form coloured compounds in terms of the frequency of light absorbed as an electron is promoted between two non-degenerate d orbitals

Answer 21

have incomplete d shells = have space for electrons to be promoted and then absorb light.
when an electrons is promoted to the higher energy level, the difference between the two non-degenerate d orbitals corresponds to a particular frequency of light absorbed and reflects the light complementary.

Question 22

ligand copperexcahnge and colur chanrg

Answer 22

The ligand exchange of [Cu(H2O)6]2+ and [Co(H2O)6]2+ by NH3 ligands causes a change in the colour of the solutions
[Cu(H2O)6]2+ is light blue in colour whereas [Cu(NH3)4(H2O)2)]2+ is deep blue in colour
[Co(H2O)6]2+ is a pink solution whereas [Co(NH3)6]2+ is a brown solution
the ligand causes d orbitals to split by a different amount of energy and so different ΔE and light frequency absorbed

Question 23

NH3 to copper sulfate

Answer 23

[Cu(H2O)6]2+ + 4NH3 –> Co(NH3)4(H2O)2(aq)+ + 4H2O

Question 24

hydrochloric acid to copper sulfate

Answer 24

[Cu(H2O)6]2+ + 4Cl- –> Cu(cl-)4(aq)+ + 6H2o

Question 25

Kstab

Answer 25

equilibrium constant for the formation of the

complex ion in a solvent (from its constituent ions or molecules)

Question 26

Kstab expression

Answer 26

same as Kc,

water not included = large in excess its concentration is considered constant

Question 27

high stability

Answer 27

higher value of Kc, higher its stability

Question 28

feasibility

Answer 28

the two values, positive to right, negative to left added to gether gives a positive value = feasible

Question 29

half equation of C2O4 2-

Answer 29

C2O4 2- –> 2CO2 + 2e-