transition metals

Question 1

properties of d-block elements

Answer 1

• high MP/BP
• shiny
• conduct electricity + heat

Question 2

what elements have special cases in electron configuration

Answer 2

• chromium and copper
• 3d fills before 4s so they both have 1 e- in 4s
• reason : stability
• half filled 3d5 and full 3d10 gives additional stability to chromium and copper

Question 3

define transition elements

Answer 3

• d-block elements that form at least one ion with a partially filled d-orbital
• scandium and zinc are d-block but no t-metals
• Sc3+ forms empty d-orbital
• Zn2+ forms full d-orbital

Question 4

properties of transition metals

Answer 4

• form compounds where the t-elements has a diff Ox. state
• form coloured compounds
• catalysts

Question 5

transition metals as catalysts

Answer 5

• Haber process - iron catalyst
• contact process to form sulphur trioxide (SO3) from oxidation of sulphur dioxide - vanadium (V) oxide catalyst (V2O5).

Question 6

Cu2+ with:

• NaOH
• excess NaOH

Answer 6

• blue solution to blue precipitate of Cu(OH)2

- no change bc ppt = insoluble

Question 7

Fe2+ with:

• NaOH
• excess NaOH

Answer 7

• pale green solution to green ppt of Fe(OH)2 (brown when exposed to air Fe(OH)3)
• no change , ppt = insoluble

Question 8

Fe3+ with:

• NaOH
• excess NaOH

Answer 8

• pale yellow sol to orange/brown ppt

- no change , ppt = insoluble

Question 9

Mn2+ with :

• NaOH
• excess NaOH

Answer 9

• pale pink sol to light brown ppt (darkens on standing)

- no change , ppt = insoluble

Question 10

Cr3+ with:

• NaOH
• excess NaOH

Answer 10

• green solution to grey/green precipitate

- in excess = dark green Cr(OH)6

Question 11

Fe2+

• NH3
• excess NH3

Answer 11

• no reaction bc don’t dissolve

- pale green to green

Question 12

Fe3+

• NH3
• excess NH3

Answer 12

• no reaction bc don’t dissolve

- pale yellow to orange/brown ppt

Question 13

Mn2+

• NH3
• excess NH3

Answer 13

• no reaction bc don’t dissolve

- same as NaOH : pale pink to light brown

Question 14

Cu2+

• NH3
• excess NH3

Answer 14

• blue to blue ppt

- ppt dissolves = deep blue solution of [Cu(NH3)4(H2O)2]2+

Question 15

Cr3+

• NH3
• excess NH3

Answer 15

• green to grey/green gel ppt

- dissolves in excess to form purple sol of [Cr(NH3)6]3+

Question 16

Zn2+ ion colour

Answer 16

• colourless

Question 17

Al3+ ion colour

Answer 17

• colourless

Question 18

ligand

Answer 18

• mol/ion
• bonds to metal ion
• forms coordinate bond
• donates a lone pair of e- into a vacant d-orbital
• H20 , :CN- , :NH3

Question 19

complex ion

Answer 19

• central metal ion surrounded by ligands

Question 20

monodentate ligand

bidentate ligand

Answer 20

• donates one pair of e- to central metal ion

- donates 2 lone pairs of e- to the central metal ion

Question 21

when is a square planar complex formed

Answer 21

• t-metals with eight d-e- in d-sub shell
• Platinum(II) , palladium (II) and gold (III)
• bond angle 90
• cis-platin drug

Question 22

stereoisomer

Answer 22

• same structural formula but a different arrangement of atoms in space.

Question 23

what types of stereoisomerism can complex ions display

Answer 23

• cis-trans

- optical

Question 24

structural formula for 1,2-diaminoethane

Answer 24

NH2CH2CH2NH2

Question 25

cis platin as an anti-cancer drug

Answer 25

- during chemotherapy - an anti-cancer drug - colourless liquid - drip into vein - forms a platinum complex inside of cells - binds onto DNA of cancerous cells - prevents division - trans molecule is ineffective

Question 26

Cu2+ reaction with NH3

Answer 26

- [Cu(H20)6]2+ + 4NH3 = [Cu(NH3)4(H20)2]2+ + 4H20 - in ammonia = pale blue - excess ammonia = dark blue - 4 NH3 ligands replace 4H2O ligands - 2 H2O left over

Question 27

Cu2+ with HCL

Answer 27

- [Cu(H20)6]2+ - add conc HCl - 6 H2O replaced by 4 chloride ligands - pale blue to green intermediate to yellow - [Cu(H2O)6]2+ + 4Cl- = [CuCl4]2- + 6H20 -

Question 28

why do only 4 Cl- ligands bond with Cu

Answer 28

- chloride ligands are larger than water ligands | - fewer chloride can fit around central Cu2+ ion

Question 29

Cr3+ with ammonia

Answer 29

- [Cr(H2O)6]3+ undergoes ligand substitution with excess NH3 - first, grey ppt of Cr(OH)3 formed - Cr(OH)3 ppt dissolves in excess NH3 to form purple [Cr(NH3)6]3+ - [Cr(NH3)6]3+ = violet