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Chem > TM > Flashcards

TM Flashcards

1
Q

Define a transition metal+-

A

An element that forms at least one stable ion with a partially filled d-sub shell

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2
Q

Characteristic properties of TMs

A

3CV
complex ion
coloured ions
catalytic properties
variable oxidation states

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3
Q

what is a ligand

A

A molecule or ion that forms a co-ordinate bind with TM by donating a pair of electrons

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4
Q

what is a complex

A

A central metal atom or ion surrounded by ligands

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5
Q

What is coordination number

A

The number of coordinate bonds to the central metal atom or ion

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6
Q

what is a mondentate ligand and examples

A

each ligand forms one coordinate bond
H2O:
Cl:-
:NH3
-:CN

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7
Q

Property NH3 and H2O ligand and why is this important

A

Similar in size and are uncharged
Exchange of these two ligands occurs without change of coordination number

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8
Q

Property of Cl lignands

A

Larger than uncharged ligands so only got 4 around TMs
Have a -1 charge so involve a change in co-ordination number

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9
Q

what is a bidentate ligand and examples

A

Each ligand forms 2 coordinate bonds
Ethane-1,2-diamine/ 1,2-diaminoethane (bonds form from the two N atoms) (something called ‘en’ ligand)
Ethanedioate ( bonds form from the 2 O- atoms)

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10
Q

what is a multi dentists ligand and examples

A

Each ligand forms 2 or more coordinate bonds
EDTA4- (forms 6 coordinate bonds, 2 from the N atoms and 4 from the O- atoms)

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11
Q

what is ‘haem’ group

A

its an iron(ii) complex with a multidentate ligand

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12
Q

what is a ‘globin’

A

a 5th bond forms to the fe2+ below the ring to a protein which is the globin

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13
Q

what is haemoglobin

A

a molecule found in red blood cells used to transport oxygen around the body. made up of a central fe2+ ion which has a coordination number of 6. it forms 4 bonds to a ring system called porphyrin. square planar arrangment

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14
Q

how is oxygen transported in the blood

A

oxygen forms a co-ordinate bond to Fe(II) in haemoglobin

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15
Q

why is carbon monoxide toxic

A

because it replaces oxygen co-ordinately bonded to Fe(II) in hemoglobin

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16
Q

how does the chelate effect occur and is it

A

occurs when a monodentate ligand is subsistuted by a bidentate or multidentate ligand.
it results in a large increase in entropy as more moles on RHS of equation due to subsistution (this is the chelate effect)

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17
Q

what is due transition mental usually form with small lignads

A

octahedral complexes

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18
Q

examples of small ligands

A

H2O and NH3

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19
Q

what isomerism can octahedral complexes display with monodentate lignads

A

cis-trans isomerism

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20
Q

what isomerism can octahedral complexes display with bidentate lignads

A

optical isomerism

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21
Q

stereoisomerism definition

A

have the same structural formula but have a different arrangement of atoms in space

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22
Q

what is cis-trans isomerism

A

where ligands can be spaced in different positions relative to one another. its a special case of E-Z isomerism. for example if you have 4of one type of ligand and 2 of another the 2 ligands that are the same can be arranged either at 90 degrees (next to each other) which displays cis isomerism or 180 degrees (opposite) which displays trans isomerism.

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23
Q

what do transition metals commonly form with larger ligands

A

tetrahedral complexes

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24
Q

examples of larger ligands

A

cl-

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25
Q

what is less commonly formed by transistion metals with larger ligands

A

square planar complexes

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26
Q

what isomerism does square planar display

A

cis-trans isomerism

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27
Q

how to tell if trans isomer or cis isomer in sqaure planar complex

A

if alike ligands are opposite to one another then it is trans isomer
if alike ligands ligands are next to each other then its cis isomer

28
Q

what is cisplatin

A

cis isomer of [PtCl2(NH3)2]

29
Q

cisplatin use

A

very effective anti-cancer drug, it works by binding to the DNA in cancerous cells and stops cell replicating
the 2 Cl- ions on the cisplatin are substituted for the two N atoms on the adjacent Guanine bases

30
Q

when does the cis isomer display optical isomerism

A

when has at least 2 bidentate ligands

31
Q

what is tollens reagent complex ion

A

[Ag(NH3)2]+ Ag+ forms the linear complex

32
Q

how are transition metals identified

A

by thier colour

33
Q

how does colour arise in transistion metals

A

when some of the wavelengths of visible light are absorbed and the remaining wavelengths of light are transmitted or reflected

34
Q

what happens when light is absorbed in transition metals

A

d electrons move from the ground state to an exited state when light is absorbed

35
Q

what is the energy and length or wavelength of colors in white light

A

ROY = lower energy, longer wavelength
G
BIV- higher energy, shorter wavelength

36
Q

the frequency of light which provides the change in energy between 2 d subshells can be found by the formulas:

A

change in energy(J)= hf or = h(c/wavelength of light)
where
h= planck constant Js
and f = frequency of light s-1
c= speed of light

37
Q

if a transition metal compounds has a large energy change between d subshells then

A

BIG E BIV abs
high energy light(BIV)
will be absorbed to excite electrons
ROY will be reflected so compounds will look red/orange

38
Q

if a transition metal compounds has a small energy change between d subshells then

A

small E ROY abs
low energy light (ROY)
will be absorbed to exite electrons
BIV will be reflected by the compound
so compound will look blue/ pourple

39
Q

what changes can alter the colour of the TM compumd

A

LOCo
change in ligands
change in oxidation state of the metal
change in coordination number of the complex

40
Q

where is the absorption of visible light used

A

spectometry

41
Q

what is a simple colorimeter used for

A

to determine the concentration of coloured ions in the solution

42
Q

how to find the concentration of an unknown sample from the calibrations curve

A

measure the absorbance of known conc
plot graph absorbance v conc
read value conc for measured absorbance
from this graph

43
Q

lower oxidation states and higher oxidation states types of ions

A

lower oxidation states exist as simple ions
higher oxidation states only form as ‘polyatomic’ ions eg manganese in the (VII) exists as the manganate ion MnO4-

44
Q

reduction of vanadium species

A

vanadate(V) ion reduced to (VO3)- or (VO4)3- or (VO2)+
in acidic conditions by solid Zinc which itself is oxidised Zn —> Zn2+ +2e-

45
Q

what is the redox potential for transition metals ion changing from a higher to a lower oxidation state influenced by

A

pH (larger in acidic solutions, some need H+ to be reduced some others releases OH- when reduced) and by the ligand(different ligands may make the redox potential larger or smaller depending on how well they bind to a particular metal ion in a particular oxidation state)

46
Q

colour change Fe2+ to Fe3+

A

green to brown

47
Q

colour change MnO4- to Mn2+

A

purple to colourless

48
Q

(Cr2O7)2- to Cr3+ colour change

A

orange to green

49
Q

what is the redox potential of on ion or atom

A

how easily it is reduced to a lower oxidation state

50
Q

how does tollens reagent use redox to distinguish between aldehydes and ketones

A

prepared by adding just enough ammonia solution to silver nitrate solution to form colorless solution containing the complex ion [Ag(NH3)2]+ when added to aldehyde tollens reagent reacts to give a silver mirror, by the aldehyde is oxidized to carboxlilic acid and Ag+ ions are reduced to silver metal

51
Q

what is a catalyst

A

speeds up rate of reaction and doesn’t get used up in reaction. works by providing an alternative reaction pathway with a lower activation energy

52
Q

transition metals and their compounds can act as

A

heterogenous and homogenous catalysts

53
Q

what is a heterogeneous catalyst

A

is in a different phase from the reactants and the reaction occurs at the active site on the surface

54
Q

what is a homogenous catalyst

A

in the same phase as the reactants and reaction proceeds through an intermediate species

55
Q

mechanism steps of heterogeneous catalyst

A

reactants adsorb onto the surface of the catalyst on an active site
reaction occurs on the surface of the catalyst
products desorb from the surface of the catalyst

56
Q

how to make heterogenous catalyst more effecient

A

increase surface area
spread the catalyst over an inert support medium

57
Q

why don’t heterogeneous catalysts last forever and how increases time they last

A

posisoning can occur
impurities can block the active sites
this prevents the reactants from adsorbing
purifying the reactants if the best way to prevent to poisinging

58
Q

catalyst for making ammonia in Haber process and the eqaution

A

catalyzed by solid iron heterogenous
N2(g) + 3H2(g) <—> 2NH3(g)

59
Q

heterogenous catalyst for making sulphric acid in the contact process and the equations

A

heterogenous catlayste solid vandium(V) oxide - V2O5(s)
1- SO2(g) + V2O5(s) <—-> SO3(g) + V2O4(s)
2- 2V2O4(s) + O2(g) <—> 2V2O5(s)
overall- 2SO2(g) + O2(g) —> 2SO3(g)
sulfuric acids then formed by reacting SO3 and H2O

60
Q

catalyst for making methanol

A

Cr2O3
heterogenous

61
Q

why in homogenous catlyst is the activation energy of the uncataluysed reaction so high

A

the two negative ions repel

62
Q

catatlyse for reaction of I- and (S2O8)2-
eqautions and why

A

Fe2+ (homogenous) needs catalyst as both negative
(S2O8)2- (aq) + 2Fe2+(aq) –> 2(SO4)2-(aq) + 2Fe3+(aq)
2I-(aq) +2Fe3+(aq) —> I2(aq) + 2Fe2+(aq)
overall equation
(S2O8)2-(aq) + 2I- –> 2(SO4)2-(aq) +I2

63
Q

what is autocatalysis

A

unusual example of homogeneous catalysis, where one of the products of the reaction actually catalyses’ the reaction as it proceeds further

64
Q

autocatalysis example in oxidation of ethanedioic ions

A

by mangate(VII) ions

65
Q

explain with the aid of eqautions how reaction between manganite (VII) ions and ethanedioate ions are catalysed

A

Uncatalysed reaction very slow :
2MnO4- +16H+ + 5C2O4 2- —-> 2Mn2+ +8H2O + 10CO2
Quickens as reaction proceeds as Mn2+ formed acts as autocalyst, reacts with MnO4- ions to form Mn3+ as an intermediate species
4(Mn)2+(aq) + MnO4-(aq) + 8H+(aq) –> 5Mn3+(aq) + 4H2O(l)
which then reacts with C2O4 2- ions to reform Mn2+
2Mn3+ (aq) + (C2O4)2-(aq) —> 2CO2(g) + 2Mn2+(aq)

66
Q

describe and explain the conc vs time graph for reaction between MnO4- and C2O4 2

A

the rate starts off slow as there is no catalyst initially.
the 2 negatively charged reactants collide with a very high Ea
then as some Mn2+ is formed the rate increases as the reaction is being increasingly catalyzed.
the rate then decreases and levels off as the reactants get used up

Chem (33 decks)

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