AQA A-LEVEL CHEMISTRY 7405/3 Paper 3
what colour is {Fe(H2O)6}2+ - ANSWER pale green
Transition Metal definition - ANSWER D block elements that form at least one stable
ion with a partially filled d orbital
Classic elements which are not transition metals despite being D-Block elements -
ANSWER Scandium and Zinc
properties of transition metals which are NOT shared by other metals - ANSWER -
multiple oxidation states
-coloured ions in solution
-great catalysts
-form complexes with ligands
ligand - ANSWER a molecule which forms a dative bond with a transition metal
complex ion - ANSWER A transition metal ion bonded to one or more ligands by
coordinate bonds
co-ordination number - ANSWER The number of co-ordinate bonds formed to a
central metal ion
What is an example of incomplete ligand substitution? - ANSWER [Cu(NH3)6]2+ to
[Cu(NH3)4(H2O)2]2+
why does the coordination number not change when substituting water for
ammonia ? - ANSWER because they are of a similar size
Why does incomplete ligand substitution usually occur? - ANSWER when
substituting ligands of a different size
Denticity - ANSWER the number of dative bonds that can be formed with a
transition metal by one ligand
bidentate - ANSWER When a ligand can form two co-ordinate bonds in a complex
ion.
monodentate (or unidentate) - ANSWER A ligand that can form one bond
Multidentate - ANSWER A ligand that can form multiple bonds
Chelate effect - ANSWER the ability of multidentate ligands to form more stable
metal complexes than those formed by similar monodentate ligands
Why is the chelate effect a largely entropic effect? - ANSWER As you the number of
moles of molecules in the products of the reaction increase. This leads to a large
increase in entropy and this brings the Gibbs free energy below zero for the change.
, Why is enthalpy change negligible in ligand substitution? - ANSWER The (dative)
bonds being broken and made are the same strength, amount and type.
Why is carbon monoxide toxic? - ANSWER CO can from a strong dative bond with
haemoglobin. This is a stronger bond than that made with oxygen and so it replaces
the oxygen attaching to the haemoglobin. This can starve the body of oxygen.
Ligand exchange/substitution - ANSWER when one ligand in a complex ion is
replaced by a different ligand
What are the four main geometries for complex ions? - ANSWER Octahedral,
Tetrahedral, Square planar, Linear
What ligands tend to form octahedral complexes? - ANSWER water and ammonia
What ligands tend to form tetrahedral complexes? - ANSWER Chloride
What ligands tend to form square planar complexes? - ANSWER Nickel, Palladium,
Platinum
What ligands tend to form linear complexes? - ANSWER Copper, silver and gold
What type of isomerism can square planar complexes exhibit? - ANSWER cis-trans
isomerism
What does cisplatin look like? - ANSWER
What does transplatin look like? - ANSWER
Formula for Tollens' reagent and what does it test for? - ANSWER (Tests for
aldehydes and forms a silver mirror)
what type of isomerism is cis-trans isomerism - ANSWER Stereoisomerism
What type of isomerism can octahedral molecules with three bidentate ligands
show? - ANSWER Optical isomerism
factors affecting shape of ligand - ANSWER -central metal ion present
-ligands
In the presence of ligands, what happens to electrons? - ANSWER The orbitals will
split. Some of them gain energy, and some of them lose energy.
What is delta E in transition metals? - ANSWER The difference in energy of the
excited state and the ground state of the electron
What happens if an electron absorbs energy equal to the energy gap of delta E? -
ANSWER it can move to occupy the higher energy orbitals. This is called an excited
electronic state.
what colour is {Fe(H2O)6}2+ - ANSWER pale green
Transition Metal definition - ANSWER D block elements that form at least one stable
ion with a partially filled d orbital
Classic elements which are not transition metals despite being D-Block elements -
ANSWER Scandium and Zinc
properties of transition metals which are NOT shared by other metals - ANSWER -
multiple oxidation states
-coloured ions in solution
-great catalysts
-form complexes with ligands
ligand - ANSWER a molecule which forms a dative bond with a transition metal
complex ion - ANSWER A transition metal ion bonded to one or more ligands by
coordinate bonds
co-ordination number - ANSWER The number of co-ordinate bonds formed to a
central metal ion
What is an example of incomplete ligand substitution? - ANSWER [Cu(NH3)6]2+ to
[Cu(NH3)4(H2O)2]2+
why does the coordination number not change when substituting water for
ammonia ? - ANSWER because they are of a similar size
Why does incomplete ligand substitution usually occur? - ANSWER when
substituting ligands of a different size
Denticity - ANSWER the number of dative bonds that can be formed with a
transition metal by one ligand
bidentate - ANSWER When a ligand can form two co-ordinate bonds in a complex
ion.
monodentate (or unidentate) - ANSWER A ligand that can form one bond
Multidentate - ANSWER A ligand that can form multiple bonds
Chelate effect - ANSWER the ability of multidentate ligands to form more stable
metal complexes than those formed by similar monodentate ligands
Why is the chelate effect a largely entropic effect? - ANSWER As you the number of
moles of molecules in the products of the reaction increase. This leads to a large
increase in entropy and this brings the Gibbs free energy below zero for the change.
, Why is enthalpy change negligible in ligand substitution? - ANSWER The (dative)
bonds being broken and made are the same strength, amount and type.
Why is carbon monoxide toxic? - ANSWER CO can from a strong dative bond with
haemoglobin. This is a stronger bond than that made with oxygen and so it replaces
the oxygen attaching to the haemoglobin. This can starve the body of oxygen.
Ligand exchange/substitution - ANSWER when one ligand in a complex ion is
replaced by a different ligand
What are the four main geometries for complex ions? - ANSWER Octahedral,
Tetrahedral, Square planar, Linear
What ligands tend to form octahedral complexes? - ANSWER water and ammonia
What ligands tend to form tetrahedral complexes? - ANSWER Chloride
What ligands tend to form square planar complexes? - ANSWER Nickel, Palladium,
Platinum
What ligands tend to form linear complexes? - ANSWER Copper, silver and gold
What type of isomerism can square planar complexes exhibit? - ANSWER cis-trans
isomerism
What does cisplatin look like? - ANSWER
What does transplatin look like? - ANSWER
Formula for Tollens' reagent and what does it test for? - ANSWER (Tests for
aldehydes and forms a silver mirror)
what type of isomerism is cis-trans isomerism - ANSWER Stereoisomerism
What type of isomerism can octahedral molecules with three bidentate ligands
show? - ANSWER Optical isomerism
factors affecting shape of ligand - ANSWER -central metal ion present
-ligands
In the presence of ligands, what happens to electrons? - ANSWER The orbitals will
split. Some of them gain energy, and some of them lose energy.
What is delta E in transition metals? - ANSWER The difference in energy of the
excited state and the ground state of the electron
What happens if an electron absorbs energy equal to the energy gap of delta E? -
ANSWER it can move to occupy the higher energy orbitals. This is called an excited
electronic state.
