AQA Chemistry A level Exam Guide
Latest Update 2026 Newest Version
Actual and Verified Answers
What makes transition metal characteristics - CORRECT ANSWERS-incomplete d sub-
level in atoms or ions
4 main characteristics of Transition metals - CORRECT ANSWERS-complex formation,
formation of coloured ions, variable oxidation state, catalytic activity
what is a complex - CORRECT ANSWERS-a central metal ion surrounded by ligands
what is a ligand - CORRECT ANSWERS-An atom, ion or molecule which can donate a
lone electron pair
what is a coordinate bond - CORRECT ANSWERS-Co-ordinate bonding is when the
shared pair of electrons in the covalent bond come from only one of the bonding atoms
what is coordination number - CORRECT ANSWERS-The number of co-ordinate bonds
formed to a central metal ion
why is carbon monoxide toxic - CORRECT ANSWERS-CO is toxic to humans as CO
can from a strong coordinate bond with haemoglobin. This is a stronger bond than that
made with oxygen and so it replaces the oxygen attaching to the haemoglobin
what is the chelate effect - CORRECT ANSWERS-The substitution of monodentate
ligand with a bidentate or a multidentate ligand leads to a more stable complex. This
chelate effect can be explained in terms of a positive entropy change in these reactions
as more molecules of products than reactants
type of isomerism shown in square planar/octahedral complexes - CORRECT
ANSWERS-E-Z
isomerism shown only in octahedral complexes - CORRECT ANSWERS-Complexes
with 3 bidentate ligands can form two optical isomers (non-superimposable mirror
images)
how do transition metals show colour - CORRECT ANSWERS-Colour arises from
electronic transitions from the ground state to excited states: between different d
orbitals.
A portion of visible light is absorbed to promote d electrons to higher energy levels. The
light that is not absorbed is transmitted to give the substance colour.
,what is the equation which links the colour and frequency of the light absorbed with the
energy difference between the split d orbitals - CORRECT ANSWERS-E = hv.
v = frequency of light absorbed (unit s-1 or Hz) h= Planck's constant 6.63 × 10-34 (J s)
E = energy difference between split orbitals (J)
how can you change colour of transition metals - CORRECT ANSWERS-Changing a
ligand or changing the coordination number will alter the energy split between the d-
orbitals, changing E and hence change the frequency of light absorbed
describe the method of spectroscopy - CORRECT ANSWERS-•Add an appropriate
ligand to intensify colour •Make up solutions of known concentration (dilution series)
•Measure absorption or transmission
•Plot graph of absorption vs concentration •Measure absorption of unknown and
compare
general trend of variable oxidation states - CORRECT ANSWERS-- Relative stability of
+2 state with respect to +3 state increases across the period
- Compounds with high oxidation states tend to be oxidising agents e.g MnO4--
Compounds with low oxidation states are often reducing agents e.g V2+ & Fe2+
four colour and symbol stages of Vanadium - CORRECT ANSWERS-VO2+ Oxidation
state +5 ( a yellow solution)
VO2+ Oxidation state + 4 (a blue solution)
V3+ Oxidation state + 3 (a green solution)
V2+ Oxidation state + 2 (a violet solution)
YOU BETTER GET VANADIUM
what is used to reduce vanadium - CORRECT ANSWERS-Addition of zinc to the
vanadium (V) in acidic solution will reduce the vanadium down through each successive
oxidation state, and the colour would successively change from yellow to blue to green
to violet
what is used in testing for aldehydes - CORRECT ANSWERS-[Ag(NH3)2]+ is used in
Tollen's reagent to distinguish between aldehydes and ketones . Aldehydes reduce the
silver in the Tollen's reagent to silver
why are dark colours of solutions difficult to measure - CORRECT ANSWERS-The
purple colour of manganate can make it difficult to see the bottom of meniscus in the
burette.
what acid is used for manganate titrations - CORRECT ANSWERS-Only use dilute
sulphuric acid for manganate titrations.
Insufficient volumes of sulphuric acid will mean the solution is not acidic enough and
MnO2 will be produced instead of Mn2+.
,Using a weak acid like ethanoic acid would have the same effect as it cannot supply the
large amount of hydrogen ions needed (8H+).
It cannot be conc HCl as the Cl- ions would be oxidised to Cl2
what is a heterogenous catalyst - CORRECT ANSWERS-in a different phase from the
reactants
what is a homogenous catalyst - CORRECT ANSWERS-in the same phase as the
reactants
what are standard conditions for heterogenous catalysts - CORRECT ANSWERS-
Heterogeneous catalysts are usually solids whereas the reactants are gaseous or in
solution. The reaction occurs at the surface of the catalyst.
how do heterogenous catalysts work - CORRECT ANSWERS-Adsorption of reactants
at active sites on the surface may lead to catalytic action. The active site is the place
where the reactants adsorb on to the surface of the catalyst. This can result in the
bonds within the reactant moleculesbecomingweaker,or themoleculesbeingheldin a
more reactive configuration. There will also be a higher concentration of reactants at the
solid surface so leading to a higher collision frequency.
how does the strength of adsorption help to determine the effectiveness of the catalytic
activity. - CORRECT ANSWERS-Some metals e.g. W have too strong adsorption and
so the products cannot be released.
Some metals e.g. Ag have too weak adsorption, and the reactants do not adsorb in high
enough concentration.
what is the effect of increasing surface area - CORRECT ANSWERS-Increasing the
surface area of a solid catalyst will improve its effectiveness. A support medium is often
used to maximise the surface area and minimise the cost (e.g. Rh on a ceramic support
in catalytic converters).
contact process equation (manufacture of sulphuric acid) - CORRECT ANSWERS-
V2O5 is used as a catalyst in the Contact Process. Overall equation : 2SO2 + O2 -->
2SO3 step1 SO2 +V2O5 --> SO3 + V2O4
step 2 2V2O4 + O2 --> 2V2O5
what are the effects of catalytic poisoning - CORRECT ANSWERS-Poisoning has a
cost implication e.g. poisoning by sulphur in the Haber Process and by lead in catalytic
converters in cars means that catalysts lose their efficiency and may need to be
replaced.
reaction between iodide and persulphate ions - CORRECT ANSWERS-The reaction
between I- and S2O82- catalysed by Fe2+
, The uncatalysed reaction is very slow because the reaction needs a collision between
two negative ions. Repulsion between the ions is going to hinder this - meaning high
activation energy.
Both of the individual stages in the catalysed mechanism involve collision between
positive and negative ions and will have lower activation energies.
overall S2O82- + 2I- --> 2SO42- + I2
Catalysed alternative route
stage 1 S2O82- + 2Fe2+ --> 2SO42- + 2Fe3+
stage2 2I- + 2Fe3+ --> 2Fe2+ + I2
Autocatalytic Reaction between Ethanedioate and Manganate ions - CORRECT
ANSWERS-overall 2MnO4- + 5C2O42- + 16H+ --> 2Mn2+ + 10CO2 + 8H2O
Catalysed alternative route
Step 1 4Mn2+ + MnO4- + 8 H+ --> 5Mn3+ + 4 H2O Step 2 2Mn3+ + C2O42- --> 2Mn2+
+ 2 CO2
what is autocatalysis - CORRECT ANSWERS-when the product of a reaction acts as a
catalyst
what is a lewis acid - CORRECT ANSWERS-electron pair acceptor (metal ion)
what is a lewis base - CORRECT ANSWERS-electron pair donor (ligand)
colour of hexaaqua iron (II) - CORRECT ANSWERS-green
colour of hexaaqua copper (II) - CORRECT ANSWERS-blue
colour of hexaaqua aluminium (III) - CORRECT ANSWERS-colourless (not a transition
metal)
colour of hexaaqua iron (III) - CORRECT ANSWERS-violet
what is a hydrolysis/acidity reaction - CORRECT ANSWERS-addition of water/removal
of a hydrogen
[M(H2O)6]2+ + H2O --> [M(H2O)5(OH)]+ + H3O+
why are 3+ ions more acidic than 2+ - CORRECT ANSWERS-The acidity of
[M(H2O)6]3+ is greater than that of [M(H2O)6]2+ in terms of the greater polarising
power (charge/size ratio) of the 3+ metal ion. The greater the polarising power, the more
strongly it attracts the water molecule. This weakens the O-H bond so it breaks more
easily.
Precipitate of Copper (II) with hydroxide or NH3 (deprotonation acid-base reaction) -
CORRECT ANSWERS-blue
Latest Update 2026 Newest Version
Actual and Verified Answers
What makes transition metal characteristics - CORRECT ANSWERS-incomplete d sub-
level in atoms or ions
4 main characteristics of Transition metals - CORRECT ANSWERS-complex formation,
formation of coloured ions, variable oxidation state, catalytic activity
what is a complex - CORRECT ANSWERS-a central metal ion surrounded by ligands
what is a ligand - CORRECT ANSWERS-An atom, ion or molecule which can donate a
lone electron pair
what is a coordinate bond - CORRECT ANSWERS-Co-ordinate bonding is when the
shared pair of electrons in the covalent bond come from only one of the bonding atoms
what is coordination number - CORRECT ANSWERS-The number of co-ordinate bonds
formed to a central metal ion
why is carbon monoxide toxic - CORRECT ANSWERS-CO is toxic to humans as CO
can from a strong coordinate bond with haemoglobin. This is a stronger bond than that
made with oxygen and so it replaces the oxygen attaching to the haemoglobin
what is the chelate effect - CORRECT ANSWERS-The substitution of monodentate
ligand with a bidentate or a multidentate ligand leads to a more stable complex. This
chelate effect can be explained in terms of a positive entropy change in these reactions
as more molecules of products than reactants
type of isomerism shown in square planar/octahedral complexes - CORRECT
ANSWERS-E-Z
isomerism shown only in octahedral complexes - CORRECT ANSWERS-Complexes
with 3 bidentate ligands can form two optical isomers (non-superimposable mirror
images)
how do transition metals show colour - CORRECT ANSWERS-Colour arises from
electronic transitions from the ground state to excited states: between different d
orbitals.
A portion of visible light is absorbed to promote d electrons to higher energy levels. The
light that is not absorbed is transmitted to give the substance colour.
,what is the equation which links the colour and frequency of the light absorbed with the
energy difference between the split d orbitals - CORRECT ANSWERS-E = hv.
v = frequency of light absorbed (unit s-1 or Hz) h= Planck's constant 6.63 × 10-34 (J s)
E = energy difference between split orbitals (J)
how can you change colour of transition metals - CORRECT ANSWERS-Changing a
ligand or changing the coordination number will alter the energy split between the d-
orbitals, changing E and hence change the frequency of light absorbed
describe the method of spectroscopy - CORRECT ANSWERS-•Add an appropriate
ligand to intensify colour •Make up solutions of known concentration (dilution series)
•Measure absorption or transmission
•Plot graph of absorption vs concentration •Measure absorption of unknown and
compare
general trend of variable oxidation states - CORRECT ANSWERS-- Relative stability of
+2 state with respect to +3 state increases across the period
- Compounds with high oxidation states tend to be oxidising agents e.g MnO4--
Compounds with low oxidation states are often reducing agents e.g V2+ & Fe2+
four colour and symbol stages of Vanadium - CORRECT ANSWERS-VO2+ Oxidation
state +5 ( a yellow solution)
VO2+ Oxidation state + 4 (a blue solution)
V3+ Oxidation state + 3 (a green solution)
V2+ Oxidation state + 2 (a violet solution)
YOU BETTER GET VANADIUM
what is used to reduce vanadium - CORRECT ANSWERS-Addition of zinc to the
vanadium (V) in acidic solution will reduce the vanadium down through each successive
oxidation state, and the colour would successively change from yellow to blue to green
to violet
what is used in testing for aldehydes - CORRECT ANSWERS-[Ag(NH3)2]+ is used in
Tollen's reagent to distinguish between aldehydes and ketones . Aldehydes reduce the
silver in the Tollen's reagent to silver
why are dark colours of solutions difficult to measure - CORRECT ANSWERS-The
purple colour of manganate can make it difficult to see the bottom of meniscus in the
burette.
what acid is used for manganate titrations - CORRECT ANSWERS-Only use dilute
sulphuric acid for manganate titrations.
Insufficient volumes of sulphuric acid will mean the solution is not acidic enough and
MnO2 will be produced instead of Mn2+.
,Using a weak acid like ethanoic acid would have the same effect as it cannot supply the
large amount of hydrogen ions needed (8H+).
It cannot be conc HCl as the Cl- ions would be oxidised to Cl2
what is a heterogenous catalyst - CORRECT ANSWERS-in a different phase from the
reactants
what is a homogenous catalyst - CORRECT ANSWERS-in the same phase as the
reactants
what are standard conditions for heterogenous catalysts - CORRECT ANSWERS-
Heterogeneous catalysts are usually solids whereas the reactants are gaseous or in
solution. The reaction occurs at the surface of the catalyst.
how do heterogenous catalysts work - CORRECT ANSWERS-Adsorption of reactants
at active sites on the surface may lead to catalytic action. The active site is the place
where the reactants adsorb on to the surface of the catalyst. This can result in the
bonds within the reactant moleculesbecomingweaker,or themoleculesbeingheldin a
more reactive configuration. There will also be a higher concentration of reactants at the
solid surface so leading to a higher collision frequency.
how does the strength of adsorption help to determine the effectiveness of the catalytic
activity. - CORRECT ANSWERS-Some metals e.g. W have too strong adsorption and
so the products cannot be released.
Some metals e.g. Ag have too weak adsorption, and the reactants do not adsorb in high
enough concentration.
what is the effect of increasing surface area - CORRECT ANSWERS-Increasing the
surface area of a solid catalyst will improve its effectiveness. A support medium is often
used to maximise the surface area and minimise the cost (e.g. Rh on a ceramic support
in catalytic converters).
contact process equation (manufacture of sulphuric acid) - CORRECT ANSWERS-
V2O5 is used as a catalyst in the Contact Process. Overall equation : 2SO2 + O2 -->
2SO3 step1 SO2 +V2O5 --> SO3 + V2O4
step 2 2V2O4 + O2 --> 2V2O5
what are the effects of catalytic poisoning - CORRECT ANSWERS-Poisoning has a
cost implication e.g. poisoning by sulphur in the Haber Process and by lead in catalytic
converters in cars means that catalysts lose their efficiency and may need to be
replaced.
reaction between iodide and persulphate ions - CORRECT ANSWERS-The reaction
between I- and S2O82- catalysed by Fe2+
, The uncatalysed reaction is very slow because the reaction needs a collision between
two negative ions. Repulsion between the ions is going to hinder this - meaning high
activation energy.
Both of the individual stages in the catalysed mechanism involve collision between
positive and negative ions and will have lower activation energies.
overall S2O82- + 2I- --> 2SO42- + I2
Catalysed alternative route
stage 1 S2O82- + 2Fe2+ --> 2SO42- + 2Fe3+
stage2 2I- + 2Fe3+ --> 2Fe2+ + I2
Autocatalytic Reaction between Ethanedioate and Manganate ions - CORRECT
ANSWERS-overall 2MnO4- + 5C2O42- + 16H+ --> 2Mn2+ + 10CO2 + 8H2O
Catalysed alternative route
Step 1 4Mn2+ + MnO4- + 8 H+ --> 5Mn3+ + 4 H2O Step 2 2Mn3+ + C2O42- --> 2Mn2+
+ 2 CO2
what is autocatalysis - CORRECT ANSWERS-when the product of a reaction acts as a
catalyst
what is a lewis acid - CORRECT ANSWERS-electron pair acceptor (metal ion)
what is a lewis base - CORRECT ANSWERS-electron pair donor (ligand)
colour of hexaaqua iron (II) - CORRECT ANSWERS-green
colour of hexaaqua copper (II) - CORRECT ANSWERS-blue
colour of hexaaqua aluminium (III) - CORRECT ANSWERS-colourless (not a transition
metal)
colour of hexaaqua iron (III) - CORRECT ANSWERS-violet
what is a hydrolysis/acidity reaction - CORRECT ANSWERS-addition of water/removal
of a hydrogen
[M(H2O)6]2+ + H2O --> [M(H2O)5(OH)]+ + H3O+
why are 3+ ions more acidic than 2+ - CORRECT ANSWERS-The acidity of
[M(H2O)6]3+ is greater than that of [M(H2O)6]2+ in terms of the greater polarising
power (charge/size ratio) of the 3+ metal ion. The greater the polarising power, the more
strongly it attracts the water molecule. This weakens the O-H bond so it breaks more
easily.
Precipitate of Copper (II) with hydroxide or NH3 (deprotonation acid-base reaction) -
CORRECT ANSWERS-blue
