A2 AQA Chem5 - Transition Metals: Complexes | Colour | Colourimetry | Redox Titrations

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  • Created by: Jamila
  • Created on: 01-06-15 16:23
What makes transition metals, transition metals?
They can form at least one uon that has an incomplete set of d electrons/
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What is a complex?
A central metal ion bonded to one or more ligand.
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Which two metals are not classed as transition metals.
Scandium Sc and Zn because they only make Sc3+ ion which is 3d0 and Zn2+ which si 3d10 which have complete d subshell.
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Which two metals half fill their 4s orbital?
Copper and Chromium
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What is a ligand?
A ligand donates lone pair of electrons to form co-ordinate bonds with a metal ion.
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What is a co-ordidnate bond?
A coordinate bond is where both pairs of electrons in a covalent bond is donated fromt he same atom.
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What shape does a complex with six ligands make and what would the bond angle of shape be?
Octahedral witha bond angle of 90 degrees. E.g. water ligand and ammonia ligands would nomrall make six coordinate bonds with a central metal ion.
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What shape does a complex with four ligands makeand what would the bond angle of shape be?
Tetrahedral with bond angle of 109.5 degrees. Chlorine is a large ligand so only four can fit around a central metal ion.
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Which complex has a square planer shape and what is its use and disadvantage?
Cis-platin has two ammonia and chloride ligands attached to a cetral platinum complex. Cis-platin si used as a nti-cancer drug, by binding to DNA and stopping it from replicating. Disadvantage is that it attachs both cancer cells and healthy cells.
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Which complex has a linear shape and what is it called and its use?
Ag3+ attached to two NH3 ligands. It is knwon as Tollens' reagent which is used to test for aldehyde. It oxidises aldehyde and forms a silver mirror in the test tube.
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What is the co-ordination number of a complex?
It is the number of lone pairs of electrons bonded to the central ion.
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What are unidente ligands and give examples of this type of ligand?
They are ligands which can donate on pair of lone electrons. Examples include H2O, NH3, Cl-, SCN- and CN-.
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What are bidente ligands and give examples of this type of ligand?
They are ligands which can donate two lone pairs of electrons such as 1,2-diaminoethane, H2NCH2CH2NH2, and ethanedioate, C2O42-.
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What are bidente ligands and give examples of this type of ligand?
They are ligands that can donate more than two lone pairs of electrons to central metal ions, such as Pophyrin and EDTA4-/
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What are mulitdente ligands and give examples of this type of ligand?
They are ligands that have more than oen atom that can donat a lone pair of electrons to a central metal ion such as porphyrin which is tetradentate and EDTA4- which is hexadentate.
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What is pophyrin.
It is a planar tetrahedrate ligand that forms four co-ordinate bonds from its N atoms with Fe2+ and forms a haem. Fe2+ can get a co-ordination number of 6 by bonding to oxygen to form oxyhaemoglobin or water to form deoxyheamoglobin.
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Why is carbon monoxide poisonous?
Oxygen bonds weakly to Fe2+ where as carbon monoxide bonds to Fe2+ in the heamoglobin. If CO binds to heamoglobin it makes it poisonous as less oxygen is being carried in the blood.
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How are transition metals colored?
When electrons absorb visible light they can be promoted to a higher energy level. Coloured light is then transmitters. The colour of the light absorbed depends on the energy gap between the the levels.
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What determines the colour of a transition metal?
The oxidation state of the metal, co-ordination number and identity of ligand determines the colour of the complex.
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What is the relationship between energy gap and the frequency of the visible light?
Energy gap = frequency of visible light x Planck's constant.
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What does a colorimeter do?
It measures absorption of radiation by a coloured solution at a particular frequency?
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What can colorimetry be used for?
It can be used to determine the concentraition of a transition metal ion solution because the amount of radiation absorbed is proportional to the concentration of the solution being tested.
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What can be added to a transition metal solution if it can not be identified by a colorimeter because it has a pale colour?
A ligand can be added to intensify the colour e.g. thiocyanate ions, SCN-, can be added to Fe3+(aq)
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Ho can you identify a transition metal using a colorimeter once you get results?
Plot a calibration graph of the absorption by solutions of known concentrations and compare it to absoption of the solution of unknown concentration.
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What are redox titrations used for?
To determine unknown concentrations using a acid-base reaction
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What happes during Iron(II) / manganate(VII) redox titration where mixture goes from colourless ti pink?
MnO4- oxidises Fe2+ to Fe3+ and is reduced to Mn2+. H2SO4 is used to provide excess H+ ions for reduction process. Also, It does not interfere with redox reaction.
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Other cards in this set

Card 2

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What is a complex?

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A central metal ion bonded to one or more ligand.

Card 3

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Which two metals are not classed as transition metals.

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Preview of the front of card 3

Card 4

Front

Which two metals half fill their 4s orbital?

Back

Preview of the front of card 4

Card 5

Front

What is a ligand?

Back

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