transition metals

Question 1

what is a transition metal

Answer 1

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

Question 2

what 4 key features do transition metals display

Answer 2

1) form complex ions
2) coloured ions- transition metal compounds are diffrent colours
3) catalytic properties- transition elements and compounds formed from transition events can act as catalysts
4) variable oxidation states
transition elements form compounds in which the metal can have different oxidation states

Question 3

what is a coordinate bond

Answer 3

shared pared of electrons that come from the same ion

Question 4

what is a ligand

Answer 4

an ion or molecule with a lone pair of electrons that can from a coordinate bong

Question 5

what is a bidentate ligand

Answer 5

2 coordinate bonds in a ligand

Question 6

coordination number

Answer 6

number of coordiante bonds

Question 7

what is a complex ion

Answer 7

centeral atom surrounded by ligands

Question 8

multi dente ligand

Answer 8

2 or more coordinate bonds formed

Question 9

name 5 monodente ligands

Answer 9

water H2O:
ammonia :NH3
hydroxide -:OH
chloride Cl:-
cynaide -:CN

Question 10

name two bidentate ligands

Answer 10

ethane-1,2-diamine
:NH2CH2CH2NH3:

ethanedioate ion
C2O4-2

Question 11

why does chloride ligands only fit 4 around

Answer 11

relatively large

Question 12

how many coordinate bonds can EDTA4- form

Answer 12

6
2 form N atoms
4 from O atoms

Question 13

when does the chelate effect occur

Answer 13

when a monodente ligand is substituted by and bidente ligand or multi dente ligand
AND THERE IS A LARGE INCREASE IN ENTROPY

Question 14

explain why ligand substation reactions are feasible

Answer 14

more moles of products then reactants
so increase in entropy/disorder
same amount of bonds broken as formed
^H IS APPROXIMATELY ZERO
^G is less then or exalt to zero making reaction feasible

Question 15

how is suffocation caused by coordinate bonds

Answer 15

O2 forms a coordinate bond to Fe2+
in hameoglobin enabling oxygen to be transported in the blood
CO is toxic because CO bonds more strongly to Fe2+ in hameglobin
this prevents O2 from forming bonds causing suffocation

Question 16

want is a stereoisomer

Answer 16

same structural formula but a diffrent arrangement in space

Question 17

trans isomer

Answer 17

2 ligands arranged opposite to each other

Question 18

what is a cis isomer

Answer 18

two ligands arranged next to each other

Question 19

why is Cis platin an anti cancer drug

Answer 19

binds to the DNA in cancer cells and stops cell replication
preventing growth and spread of cancer cells

Question 20

how do you find out which optical isomer is present

Answer 20

optical isomers rotate a plane of polarised light in opposite directions

Question 21

describe the energy of diffrent colours of light

Answer 21

ROY -low energy
G
BIV- high in energy

Question 22

why do transition metal compounds appear coloured

Answer 22

they have partially filled 3d subshells
in a transition metals all d orbitals are equal in energy (GROUND STATE)
the presence od other atoms causes the d orbitals to have slightly diffrent energies
this enables electrons to be excited from one d subshel to another
when an electron moves from a low energy subshel to a higher one the energy needed to make the transition is taken from white light
the colour of the light absorbed is then missing from the light which is reflected
the colours are transmitted give the compound is colour

Question 23

change in E can be found using what formula

Answer 23

^E=hv
^E is change in energy gained by the excited electron
h is planks constant
v is frequency of light

Question 24

explain big E BIV absorption

Answer 24

large increase in energy between d sub shells
high energy light absorbed to excite electrons
red orange yellow reflected
so looks red orange

Question 25

what things can alter the colour of a compound

Answer 25

change in ligands oxidation state coordination number shape of a complex

Question 26

what does colorimetry do

Answer 26

determine the unknown concentration of transition metal ions by measuring the amount of lights transmitted threw a sample

Question 27

describe the experimental method

Answer 27

an appropriate ligand is added to solution in order to intensify colour a range of solutions of same complex ion are made of known concentrations one at a time they are tested in a colorimeter the transmission is measured a graph is plotted of conc vs transmission and line of best flirt drawn the transmission of unknown solution is measured in a colorimeter and it’s concentration is determined by a reading off the calibration curve

Question 28

what affects the amount absorption in the experimental method of measuring absorpion

Answer 28

length of container the solution is in diluted filters used in the colorimeter which allows one colour of light threw the sample

Question 29

how do you calibrate in order to measure absorption of unknown solution

Answer 29

cuvette is filled with water and put in the colorimeter and set to zero this ensure accuracy and negated absorbsnce due to solution

Question 30

what is a catalyst

Answer 30

a substance that increases the rate of a chemical reaction without being used up

Question 31

how does a catalyst work

Answer 31

provides an alternative reaction pathway with a lower activation energy

Question 32

what is a heterogeneous catalyst

Answer 32

diffrent phase to reactant

Question 33

what is a homogeneous catalyst

Answer 33

same phase an the reactants

Question 34

how do heterogenous catalysts work

Answer 34

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

Question 35

how do you make a catalyst most effectent

Answer 35

increase surface area spread the catalyst over an inert support medium

Question 36

how can poison of catalyst occur

Answer 36

impurities blocking the active sites prevents the reactants from adsorbing purifying the reactants in the best way to prevent poisoning

Question 37

name 3 heterogeneous catalyst examples

Answer 37

making ammonia in the haber process catalysed by solid iron making sulfuric acid in the contact process catalysed by solid vandium oxide manufacturing of methanol catalysed by solid chromium oxide

Question 38

why can transition metals act as catalysts and group 1 metals can’t

Answer 38

they have variable oxidation states

Question 39

example of homogenous catalyst you must no

Answer 39

peroxodisulfate ions oxsdise iodide ions to iodine the uncatalyzed reaction has high activation energy as the 2 negative ions repel each other Fe2+ catalyses it in a 2 step process S2O8 + 2Fe2+ -> 2SO42- + 2Fe3+ 2I- + 2Fe3+ -> I2 + 2Fe2+ both steps then are between positive and negative ions in the second step the catalyst is regenerated

Question 40

what is an autocatalyst

Answer 40

a homogeneous catalyst where one of the products of the reaction actually catalyses the reaction as it proceeds further e.g oxidation of ethanedioic acid and managaate ions

Question 41

describe the oxidation of ethanedioic acid by magnate ions

Answer 41

the rate starts of slow as there is no catalyst intially 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 catalysed the rate then decreases and levels off as the reactants get used up

Question 42

why is the titration of Fe2+ and MnO4 self indicating

Answer 42

as the MnO4- reactants to form Mn2+ it turns from deep purple to colourless as the MnO4- is added to the Fe2+ solution it decolourises as it reacts as soon as all the Fe2+ is reacted the reaction mixture will start to turn pale pink as the MnO4- has nothing to react with purple (MnO4-) + (Fe2+) pale green goes pink Fe3+ ?