transition metals

Question 1

what feature do transition metals have in terms of their orbitals

Answer 1

they contain a partially full d-orbital (d sub-shell)

Question 2

uses of iron

Answer 2

vehicle bodies, to reinforce concrete

Question 3

use of titanium

Answer 3

jet parts

Question 4

use of copper

Answer 4

water pipes

Question 5

chemical properties of transition metals

Answer 5

-variable oxidation states
-form coloured complexes
-form complex ions
-act as catalysts

Question 6

define the term complex ion

Answer 6

central transition metal ion surrounded by ligands that are datively (co-ordinately) bonded to it

Question 7

give some examples of transition metal catalysts and the process they catalyse

Answer 7

-haber process, iron
-contact process, vanadium
-permanganate, decomposition of hydrogen peroxide

Question 8

define the term ligand

Answer 8

an ion or molecule with at least one lone pair of electrons that can be donated to the central transition metal ion via a co-ordinate bond

Question 9

define bidenetate and multidentate ligands

Answer 9

bidentate, forms two co-ordinate bonds with the central transition metal ion
-multidentate, can form 3 or more co-ordinate bonds with the central transition metal ion

Question 10

give some examples of monodentate ligands

Answer 10

water, ammonia, chloride

Question 11

define the term co-ordination number

Answer 11

the number of co-ordinate bonds the central transition metal ion has made with its ligands

Question 12

what is the chelate effect

Answer 12

chelate complexes with multidentate ligands are favoured over monodentate ligands

Question 13

explain the chelate effect in terms of entropy and thermodynamics

Answer 13

-number of molecules increases when multidentate ligands such as EDTA displace other ligands that form fewer co-ordinate bonds per molecule
-increase in entropy so the value of gibbs free energy decreases to become more negative, so reaction becomes more pheasible
-a more stable complex is formed

Question 14

what shape does a complex with 4 ligands usually exist as

Answer 14

tetrahedral

Question 15

name an exception for a complex that doesn’t form a tetrahedral shape and give the shape it forms

Answer 15

-platin
-exists as square planar
-forms cisplatin

Question 16

what types of isomerism can complexes display

Answer 16

-can display geometric (E/Z or cis/trans) isomerism depending on the location of ligands in octahedral and square planar molecules
-optical isomerism only exists in cis bidentate or cis multidentate complexes

Question 17

what happens when replacing monodentate ligands in a complex with chloride ions

Answer 17

co-ordination number decreases from 6 to 4 as the chloride ligand is much larger

Question 18

what is haem and its features

Answer 18

molecule that makes up protein chains, made from a Fe2+ ion with 6 co-ordinate bonds
-4 of these bonds are in a porphyrin ring system

Question 19

how does haemoglobin carry oxygen around the body

Answer 19

forms a weak co-ordinate bond to the Fe2+ ion
-carried around body, then bond is broken once oxygen reaches target cell

Question 20

why is carbon monoxide toxic

Answer 20

CO also co–ordinately bonds to the central Fe2+
-CO is a better ligand than oxygen so prevents oxygen binding to haemoglobin

Question 21

how are transition metal complexes coloured

Answer 21

-absorbs all colours, reflects certain ones, which we see
-partially filled d sub-shells allow electrons to move between energy levels
-electrons can absorb photons of light and become excited and move up energy levels
-electrons then de-excite and release thermal energy
-colour corresponding to the frequency of the energy change are missing from spectrum, so we see a combination of colours that aren;t absorbed

Question 22

what can you use to reduce vanadium

Answer 22

zinc ( in acid, i.e HCl)

Question 23

what colour is Fe2+ aqua ions

Answer 23

green

Question 24

what colour is Fe3+ aqua ions

Answer 24

brown

Question 25

what colour are permanganate ions

Answer 25

deep purple

Question 26

what colour is Mn2+ ions

Answer 26

pink

Question 27

define a catalyst

Answer 27

-a substance that speeds up a chemical reaction without being used up itself

Question 28

how does a catalyst work

Answer 28

-provides an alternate pathway with lower activation energy

Question 29

what is catalytic poisoning

Answer 29

unwanted impurities adsorb onto the catalyst’s surface and blocks the active site of the catalyst’s surface

Question 30

what are all the colours for the different oxidation states of vanadium

Answer 30

vanadium (II), purple
vanadium (III), green
vanadium (IV), blue
vanadium (V), yellow