The transition metals
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- Created by: r98
- Created on: 24-04-16 15:24
What are some physical properties of the elements from titanium to copper?
They're metals, they're good conductors of heat and electricity. They're hard, strong, shiny, and have high melting & boiling points.
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Do transition metals have high or low chemical reactivity?
Fairly low chemical reactivity.
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What is the electronic configuration of Chromium, Cr? (using the noble gas configuration)
[Ar] 3d^5 4s^1.
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What is the electronic configuration of Copper, Cu? (using the noble gas configuration)
[Ar] 3d^10 4s^1.
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With all transition elements, which electrons are lost first? Why?
The 4s electrons, because they are of the highest energy.
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What is the definition of a transition element?
It's one that forms at least one stable ion with a part full d-shell of electrons.
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What are the four main features of transition metals?
Variable oxidation states, colour, catalysis, & complex ion formation.
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How is a complex ion formed?
It's formed when a transition metal ion is surrounded by ions or other molecules (ligands), which are bonded to it by co-ordinate bonds.
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What does the term 'ligand' mean?
An ion or molecule with a lone pair of electrons that forms a co-ordinate bond with a transition metal.
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How are the co-ordinate (dative) bonds formed between metals ions and ligands?
Metal ions can accept electron pairs from other ions or molecules, forming a co-ordinate bonds.
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When ligands bond to a single transition metal ion, what is the resulting species called?
A complex ion.
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What does the term 'co-ordination number' refer to?
The number of co-ordinate to ligands that surround the transition metal ion.
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Usually, what is the shape of ions with a co-ordination number of six?
Usually octahedral.
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Usually, what is the shape of ions with a co-ordination number of four?
Usually tetrahedral.
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What does the term 'multidentate ligand' mean?
The ligand has more than one lone pair of electrons which can bond to a transition metal ion.
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How many co-ordinate bonds can ethane-1,2,-diamine (aka 1,2-diaminoethane), & benzene-1,2-diol form with a transition metal ion? What do we call these type of ligands?
2 co-ordinate bonds each. They're bidentate ligands.
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How many co-ordinate bonds can the ion ethylenediaminetetracetate (EDTA^4-) form with a transition metal ion? What in the name of this type of ligand?
6 co-ordinate bonds. It's a multidentate (hexadentate) ligand.
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What are complex ions with polydentate ligands called?
Chelates.
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What can chelates be used for?
To remove d-block metal ions from solution.
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Why can fewer chloride ion ligands fit around the central metal ion, than ammonia molecules?
Because the chloride ion is a larger ligand than the ammonia molecule.
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Apart from tetrahedral, what other shape can complex ions with a co-ordination number of four have?
Square planar shape.
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Do complex ions always have a positive charge?
No, complex ions can have a positive or a negative charge.
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How does cis-platin work?
By bonding to (forming co-ordinate bonds with) DNA so that it prevents the replication of cancerous cells, as it prevents the double helix unwinding.
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Why are transition metal complexes coloured?
They have part-filled d-orbitals,e-'s can move from one d-orbital to another. Other atoms nearby make the d-orbitals have different energies,when e-'s move to a higher energy d-orbital they absorb energy in the visible region of spectrum.
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What does the colour of a transition metal complex depend on?
The oxidation state of the metal and also the ligands (and therefore shape of the complex ion as well).
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What is the colour of the [Fe(H2O)6]^2+ complex ion?
Green.
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What is the colour of the [Fe(H2O)6]^3+ complex ion?
Very pale violet.
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What is the colour of the [Cr(H2O)6]^2+ complex ion?
Blue.
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What is the colour of the [Cr(H2O)6]^3+ complex ion?
Red-violet.
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What is the colour of the [Co(NH3)6]^2+ complex ion?
Brown.
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What is the colour of the [Co(NH3)6]^3+ complex ion?
Yellow.
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In acidic solution, will potassium manganate(VII) act as an oxidising or reducing agent?
It acts as an oxidising agent.
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What is the half equation for the reduction of Mn(VII) to Mn(II)?
MnO4^-(aq) + 5e- + 8H+(aq) -----> Mn^2+(aq) + 4H2O(l)
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What is the half equation for the oxidation of iron(II) to iron(III)?
Fe^2+(aq) -----> Fe^3+(aq) + e-
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What is the overall equation for the redox reaction between acidified potassium manganate(VII) with Fe^2+(aq)?
5Fe^2+(aq) + MnO4^-(aq) + 8H+(aq) -----> 5Fe^3+(aq) + Mn^2+(aq) + 4H2O(l)
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What is the half equation for the reduction of dichromate(VI) to chromate(III)?
Cr2O7^2-(aq) + 14H+(aq) + 6e- -----> 2Cr^3+(aq) + 7H2O(l)
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What is the overall equation for the redox reaction between acidified potassium dichromate(VI) with Fe^2+(aq)?
Cr2O7^2-(aq) + 6Fe^2+(aq) + 14H+(aq) -----> 6Fe^3+(aq) + 2Cr^3+(aq) + 7H2O(l)
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Why does oxidation of lower oxidation states of transition metal ions tend to happen in alkaline solution?
Becuase in alkaline solution, there's a tendency to form negative ions.
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What is often first added, when oxidising a transition metal to a high oxidation state?
First add alkali, followed by an oxidising agent.
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In aqueous solution what does Cr(VI) exists as? What are the colours of each species?
Either the chromate(VI) ion, CrO4^2- (yellow), or as the dichromate(VI) ion Cr2O7^2- (orange).
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What is formed when sodium hydroxide is added to a solution of a chromium(III) salt? How about when the sodium hydroxide is in excess?
A green precipitate is formed, this dissolves in excess sodium hydroxide to give a green solution.
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What is the equation for the reaction between sodium hydroxide and a solution of chromium(III) salt?
[Cr(H2O)6]^3+(aq) + 3OH-(aq) -----> [Cr(OH)3(H2O)3](s) + 3H2O(l)
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What's the equation for the reaction between [Cr(OH)3(H2O)3](s) and sodium hydroxide?
[Cr(OH)3(H2O)3](s) + 3OH-(aq) -----> [Cr(OH)6)]^3-(aq) + 3H2O(l)
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What are the four forms that chromium can exist in? What are their colours?
Cr2O7^2- (orange), CrO4^2- (yellow), Cr^3+ (green), Cr^2+ (blue).
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What is the overall equation for the reduction of chromium(VI) by zinc in acid solution?
Cr2O7^2-(aq) + 14H+(aq) + 3Zn(s) -----> 2Cr^3+(aq) + 7H2O(l) + 3Zn^2+(aq)
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What is the equation for the oxidation of [Cr(OH)6]^3-(aq) using hydrogen peroxide? What is the colour of the resulting solution?
2[Cr(OH)6]^3-(aq) + 3H2O2(aq) -----> 2CrO4^2-(aq) + 2OH-(aq) + 8H2O(l)
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What's the equation for the oxidation of cobalt(II) to cobalt(III) using hydrogen peroxide?
2[Co(OH)6]^4-(aq) + H2O2(aq) -----> 2[Co(OH)6]^3-(aq) + 2OH-(aq)
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What is the equation for the reaction of [Co(H2O)6]^2+(aq) with ammonia solution?
[Co(H2O)6]^2+(aq) + 2OH-(aq) -----> Co(H2O)4(OH)2(s)
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What is the equation for the reaction of Co(H2O)4(OH)2(s) with excess ammonia? What colour is the resulting complex?
Co(H2O)4(OH)2(s) + 6NH3(aq) -----> [Co(NH3)6]^2+ + 2OH-(aq) + 4H2O(l). The complex ion is a brownish colour.
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What ion is produced when [Co(NH3)6]^2+ is oxidised by air? What is the colour of this ion?
[Co9NH3)6]^3+. It's yellow.
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What is the equation for the aerial oxidation of [Co(NH3)6]^2+?
4[Co(NH3)6]^2+(aq) + O2(g) + 2H2O(l) -----> 4[Co(NH3)6]^3+(aq) + 4OH-(aq)
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What is the colour of Co^2+?
Pink.
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What 2 groups can catalysts be divided into?
Heterogeneous & homogeneous.
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What are heterogeneous catalysts?
They are catalysts that are present in a reaction in a different phase (solid, liquid or gas) than the reactants.
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What phase are heterogenous catalysts usually in? Where does their catalytic action occur on?
They're usually present as solids, while the reactants may be gases or liquids. Their catalytic action occurs on the solid surface.
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What are two ways of making catalysts more efficient?
Increase their surface area & spread the catalyst onto an inert support medium (increases the surface-to-mass ratio)
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What 2 things can happen to catalysts over time?
They can be poisoned; the surface may become covered with unwanted impurities. Also, the finely divided catalyst may gradually be lost from the suppor medium.
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What type of catalyst is used in the Haber process? What happens to this catalyst over time?
An ifon catalyst (heterogeneous). It lasts about five years before it becomes poisoned by impurities (e.g. sulfur compounds) in the gas stream.
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Does the Contact process use a heterogeneous or homogeneous catalyst?
Heterogeneous catalyst.
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What does the Contact process produce?
Sulfuric acid.
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What is the equation for the Contact process?
2SO2 + O2 2SO3
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What is the catalyst in the Contact process?
Vanadium(V) oxide.
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What is the equation of the reaction between vanadium(V) oxide and sulfur dioxide? What is oxidised and what is reduced?
SO2 + V2O5 -----> SO3 + V2O4. Sulfur dioxide is oxidised to sulfur trioxide, vanadium(V) oxide is reduced to vanadium(IV) oxide.
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What's the equation for the reaction between vanadium(IV) oxide and oxygen?
2V2O4 + O2 -----> 2V2O5
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What is vanadium(V) oxide also known as?
Vanadium pentoxide.
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What is the equation for the production of synthesis gas from methane and steam?
CH4(g) + H2O(g) -----> CO(g) + 3H2(g)
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What is the equation for the reaction of synthesis gas to produce methanol? What can catalyse this reaction?
CO(g) + 2H2(g) -----> CH3OH(g). Chromium oxide, Cr2O3, or a mixture of copper, zinc oxide and aluminium oxide can catalyse this reaction.
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What is a homogeneous catalyst?
When the catalyst is in the same phase as the reactant, an intermediate species is formed.
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What is the equation for the overall reaction between peroxodisulfate ions, S2O8^2-, and iodide ions? What is the catalysts in this reaction?
S2O8^2-(aq) + 2I-(aq) -----> 2SO4^2-(aq) + I2(aq). The catalyst is Fe^2+ ions.
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What is the equation for the reaction in which peroxodisulfate ions oxidise iron(II) to iron(III)?
S2O8^2-(aq) + 2Fe^2+(aq) -----> 2SO4^2-(aq) + 2Fe^3+(aq).
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What is the equation for the reaction in which Fe^3+ oxidises iodide ions?
2Fe^3+(aq) + 2I-(aq) -----> 2Fe^2+(aq) + I2(aq)
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Why does the uncatalysed reaction between peroxodisulfate ions, S2O8^2-, and iodide ions have a high activation energy?
Because the reaction takes place between two ions of the same charge (both negative), which repel. Whereas, both steps of the catalysed reaction involve reactions between oppositely charged ions.
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What is autocatalysis?
When one of the products of the reaction is a catalyst for the reaction.
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How does the rate of reaction change during an autocatalysed reaction?
The reaction starts slowly at the uncatalysed rate. As the conc of one of the products (which is also a catalyst) builds up, the reaction speeds up to the catalysed rate. It now behaves like a normal reaction, slowing down as reactants are used up.
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What is the overall equation for the autocatalysed reaction between ethanedioic acid and acidified potassium manganate(VII)?
2MnO4^-(aq) +16H+(aq) + 5C2O4^2-(aq) -----> 2Mn^2+(aq) + 8H2O(l) + 10CO2(g)
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What is the intermediate formed in the autocatalysed reaction between ethanedioic acid and acidified potassium manganate(VII)? How is this intermediate formed? What does this intermediate react with?
The intermediate is Mn^3+. Once a little Mn^2+ has formed, it can react with MnO4-ions to form Mn^3+ as an intermediate species, which then reacts with C2O4^2- ions to reform Mn^2+.
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What is the equation for the formation of Mn^3+ ions in the autocatalysed reaction between ethanedioic acid and acidified potassium manganate(VII)?
4Mn^2+(aq) + MnO4^-(aq) + 8H+(aq) -----> 5Mn^3+(aq) + 4H2O(l)
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What is the equation for the reaction of Mn^3+ ions with C2O4^2- ions?
2Mn^3+(aq) + C2O4^2-(aq) -----> 2CO2(g) + 2Mn^2+(aq)
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What is the colour of the MnO4^- ion?
Purple.
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Other cards in this set
Card 2
Front
Do transition metals have high or low chemical reactivity?
Back
Fairly low chemical reactivity.
Card 3
Front
What is the electronic configuration of Chromium, Cr? (using the noble gas configuration)
Back
Card 4
Front
What is the electronic configuration of Copper, Cu? (using the noble gas configuration)
Back
Card 5
Front
With all transition elements, which electrons are lost first? Why?
Back
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