topic 15- transition metals

Question 1

d block elements

Answer 1

less sharp differences
similarities across periods are greater

Question 2

chromium and copper

Answer 2

fills d orbital before s
arrange so have the lowest energy
less repulsion

Question 3

ion formation

Answer 3

when loose or gain an electron it is lost/gained from 4s first so it is written second rather than first

Question 4

what are transition metals
-def
-characteristics

Answer 4

dblock element which forms one or more stable ions with incomplete d orbitals
-hard solids
-high melting and boiling
-catalst
-coloured ions and compounds

Question 5

ligands

Answer 5

species bonded to the metal ion by co-ordiate bonds (dative)
donate a pair of electrons to metal ions
transition metals with ligins are complex ions that carry a charge

Question 6

coordination number

Answer 6

number of cooridinate bonds from the ligands to the central metal ions

Question 7

types of ligands

Answer 7

monodentate - single lone pair
bidentate - two lone pairs
-1,2-diaminoethane
multidentate - multpiple lone pairs
-EDTA (ethylenediaminetetraacetic acid)

Question 8

chelates

Answer 8

transition metals held in claw - the bond

Question 9

naming complex ions

Answer 9

number of ligins prefix
-mono di tetra
name the ligands ending in o for ions
- chloro hydroxo
amine for NH3 and aqua for H2O
name the central metal ion
neutral and positive - naomal name
negative - latinaised name + ate
add oxidation number for central metal

Question 10

octahedral

Answer 10

coordination number of 6

Question 11

tetrahedral

Answer 11

4

Question 12

sqaure planar

Answer 12

4
cistrans isomerism
e.g cis-platin trans-platin
-cis can be used in cancer treatment but trans cannot

Question 13

linear

Answer 13

2

Question 14

equation linking energy and frequency of light

Answer 14

ΔE = h𝝂
where ΔE = change of energy
h = Planck’s constant
𝝂 = frequency

Question 15

what makes colours of transition metals

Answer 15

d orbitals split due to ligands
electrons absorb light in the visible region of the spectrum
to promote electrons to higher energy levels
the unabsorbed light is the colour shown/reflected

Question 16

stability of complexes

Answer 16

comparison of stabilities of two complexes where the number of ligands has changed

Question 17

types of reaction of ligands

Answer 17

redox
acid base
ligand exchange
coordination number change

Question 18

types of reaction of ligands
-redox

Answer 18

the oxidation number of the transition metal ion changes
-Fe+ (aq) is pale green but when exposed to air turns yellow
+2 to +3

Question 19

types of reaction of ligands
-acid base reaction

Answer 19

one or more of the ligands gains or looses a hydrogen ion
-hexaaquacopper ions react with hydroxide ions OH- remove hydrogen ions from water ligands attached to copper in acid base
isoluble neutral complex formed - blue precipitate

Question 20

types of reaction of ligands
-ligand exchange

Answer 20

one or more of the ligands around the central transition metal is replaced by a different ligand
-when excess amonia is added to hexaaquacopper ions ligand exchange occurs deep blue solution of tetraaminediaquacopper formed

Question 21

types of reaction of ligands
-coordination number change

Answer 21

the number of ligands changes
-conc hcl added to hexaaquacopper the six water are replaced by four chlorine
blue to green to yellow
coordiantion 6-4

Question 22

haemaglobin

Answer 22

in a haem group 4 n atoms hold Fe2+ ion by forming dative bonds in the square planar structure
fifth dative bond from protein to Fe2+ ion
oxygen binds by becoming ligand to Fe2+
-reversible reaction as bond is weak

Question 23

carbon monoxide

Answer 23

lone pair on carbon that forms ligand
strong bond between carbon and oxygen so takes oxygen from Fe2+
-ligand substitution
non reversible reaction

Question 24

amphoteric reaction

Answer 24

ability of a species to react with both acid and bases

Question 25

cobalt complexes reaction with alkali

Answer 25

sodium hydroxide to hexaaquacobalt -pink solution forms blue precipitate -acidbase reaction -two hydroxide removed two hydrogen from water ligands and converted into water molecules ammonia and hexaaquacobalt -same reaction -when ammonia used in excess the precipitate dissolves to form brown solution - ligand exchange

Question 26

cobalt complexes with hcl

Answer 26

conc hcl and hexaaquacobalt pink to blue -ligand exchange -change in coordination number

Question 27

iron ii complex with alkali

Answer 27

sodium hydroxide to hexaaquairon(ii) -pale green sol forms green precipitate -acid base -water mol that lost hydrogen ions are now hydroxide ligands ammonia to hexaaquairon(ii) -same observations -when left standing the green gradualy changes to brown

Question 28

reaction of iron iii complexes with alkalis

Answer 28

sodium hydroxide to hexaaquairon(iii) ion -yellow-brown sol forms brown precipitate acid base oh- remvoes 3 water ligands and converted into water molecules -now hydroxide ligand aqueous ammonium to hexaaquairon(iii) -same observations

Question 29

shapes of ligand complexes

Answer 29

no of dative bonds shape move to minimise repulstion

Question 30

cromium ion with water

Answer 30

hydrogen ion is lost from a water ligand forms hexaaquachromium water is a base complex ion is acid

Question 31

chromium ion with hydroxide

Answer 31

hydroxide remove H+ from water ligands three hydrogens removed forms complex ion with no charge -neutral complex insoluble in water and precipitate formed reaction will continue

Question 32

chromium with ammonia

Answer 32

ammonia acts as a base and a ligand green sol > green precip > violet solution

Question 33

oxidation of chromium iii to chromium vi

Answer 33

excess of sodium hydroxide added to hexaaquachromium iii to form green hexahydroxochromate iii ions then oxidised by warming with hydrogen peroxide sol forms bright yellow sol of chromate vi ions

Question 34

chromium vi to hexahydroxochromate

Answer 34

add dilute sulfuric acid to yellow to form orange

Question 35

equilibrium shift

Answer 35

increae hydrogen - side with least gas particles increase hydroxide -side with most hydrogen ions as reacts with them so moves to replace

Question 36

drichromate vi with zinc and acid

Answer 36

e.g pottasium dichromate can be reduced to chromium iii to chromium ii needs to allow hydrogen out but stop oxygen getting in -can use cotton wool

Question 37

pottasium dichromate is used for

Answer 37

seconadary alcohols to keytones primary alcohols to aldehydes primary alcohols to carboxylic acids

Question 38

oxidation states of vanadium

Answer 38

+5-yellow/-VO2^+ green as mixture of yellow and blue +4-blue-VO^2+ +3-green-V^3+ +2-violet-V^2+

Question 39

reduction agent vanadium

Answer 39

has to be more negative than all the steps in order to occur

Question 40

hetrogenous catalyst

Answer 40

reactions adsorbed onto surface on active sites weaken bonds change orientation products deadsorb can have too high or too low adsorbtion

Question 41

catalyst poisioning

Answer 41

other substances adsorb onto surface blocking active sites hard to remove

Question 42

homogenous catalysts

Answer 42

mostly reactions in solution catalyst reacts to form intermediate forms a product faster than the original and regenerates catalyst

Question 43

transition metal catalysts

Answer 43

works by varying oxidation state