Transition Metals

Question 1

What’s a complex ion

Answer 1

A central metal ion surrounded by ligands

Question 2

What’s a ligand

Answer 2

Molecules/ ions which donate a pair of electrons forming coordinate bonds

Question 3

What’s a coordinate bond

Answer 3

One of the bonded atoms provide both electrons in the covalent bond

Question 4

What’s the vanadium colours and the oxidation states

Answer 4

+2, (V²⁺): purple
+3 (V³⁺): green
+4 (VO²⁺): blue
+5 (VO₄²⁻): yellow

You’d Better Getting Practicing

Question 5

What is haemoglobin

Answer 5

Haem is a multidentate ligand that is found in the molecule haemoglobin
It’s a protein and used to transport oxygen around the body in blood

Question 6

What happens when electrons absorb light

Answer 6

• They move from the group state to the excited state
• the side of the energy change depends on the central ion and oxidation state and the coordinate number

Question 7

Why are 3+ metal aqua ions more acidic than 2+ metal aqua ions

Answer 7

Because the metal aqua ion have a higher charge it’s more polarising to the surrounding bonds this makes it easier to loose the O - H bond in water

Question 8

What are the Chromium oxidation state colours

Answer 8

+2 : blue
+3 : green
+4 : colourless
+5 : colourless
+6 : orange

Question 9

What is tollens reagent

Answer 9

It contains the silver transition metal which forms a complex ion which is used to distinguish between aldehyde and ketones

Question 10

What are amphoteric metal hydroxides

Answer 10

Metal hydroxides that can act as an acid or base which means they are amphoteric

Question 11

What does adding ammonia to metal aqua ions do

Answer 11

Adding ammonia to a metal aqua ions which forms a metal hydroxide precipitate

Question 12

What does adding excess ammonia to metal aqua ions do

Answer 12

Leads to ligand exchange

Question 13

How does haemoglobin transport oxygen

Answer 13

Haemoglobin has a water molecule bonded to it which the oxygen molecule easily replaces and when it gets to where it needs to it breaks off

Question 14

Why is breathing carbon monoxide (CO) dangerous

Answer 14

The CO molecule replaces the water ligand on the haemoglobin and it bonds strongly to the haemoglobin so oxygen can’t easily replace it and so O2 can’t be transported

Question 15

test for cooper (II) ions

Answer 15

• ammonia
  add excess ammonia and a dark blue precipitate will form
  [Cu(NH3)4]+2(aq)
• sodium hydroxide
  by adding sodium hydroxide a light blue precitate will form
  Cu2+ + 2OH − →Cu(OH)2(s)

Question 16

when is a yellow precipitate formed with hexaaqua copper(II) ions

Answer 16

when hexaaqua copper(II) reacts with concentrated chloride to form tetrachloride copper(II) is formed

Question 17

what is ligand substitution

Answer 17

its where one ligand is replaced by another ligand

Question 18

how does different sized ligands affect a complex ion

Answer 18

if the ligand that is replacing another ligand is bigger there would be less coordinate bonds round the central metal
(e.g. chloro ligands can only bond 4 times to copper)

Question 19

what affects the amount of coordinate bonds

Answer 19

• the size of the ligand
• the amount of coordinate bonds a ligand can form (e.g. bidentate ligands)

Question 20

what makes affects feasibility in a ligand substitution reaction

Answer 20

• when ligands are replaced by those that form more co-ordinate bonds there is a significant increase in entropy
• when ligands are replaced by those that form less co-ordinate bonds there is a decrease in entropy
• if there is an entropy decrease the bonds wont be feasible as ΔH is most times negligible

Question 21

why do metal complex ion become harmless when reacted with EDTA

Answer 21

EDTA is a chelating agent these are good at bonding to metal ions and difficult to remove this makes the metal ions harmless as it cant bond to anything else

Question 21

what is a chelating agent

Answer 21

these are ligands that form more than one coordinate bond and are very good at bonding to metal ions

Question 22

what is the ΔH in many ligand substitution reactions and why

Answer 22

the ΔH is negligible in many of these reactions as the same number of bonds are being broken and formed

Question 23

what is the chelate affect

Answer 23

in general ligand substitution reactions where ligands are replaced by those that form more co-ordinate bonds the reaction is feasible and this is driven by an entropy increase

Question 24

why are complexes coloured

Answer 24

• in transition metals the 5d orbital do not all have the same energy
• the gap in energy between d orbitals correspond to the energy of UV/ visible light
• the electrons absorb UV/visible light tot provide the energy to promote electrons the a higher energy
• the gap between the higher and lower d orbitals are ΔE

Question 25

what factors affect the colour of transition metals and why

Answer 25

• the central metal ion
• oxidation state of the metal
• the ligands
• the coordinate number

this is beacsue the affect the size of the energy gap

Question 26

how does concerntration affect absorbancy

Answer 26

the more concerntrated the more light it absorbs

Question 27

a sample of ammonia vandate was mixed with HCL in a flask Zn was added a

what do you do when the colour of a complex is weak

Answer 27

you add a ligand such as “bipy” to increase the absorbancy so the colour is stronger