AQA A Level Chemistry - Paper 3

AQA A Level Chemistry - 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 electro