Transition Metals and their Chemistry - exam practice
Transition Metals and their Chemistry
Question 1 of 21
Vanadium(V) oxide acts as a catalyst in the oxidation of sulfur dioxide in the Contact process.
State the meaning of the term heterogeneous as applied to catalysts.
Give two equations to describe how V2O5 acts as a catalyst in this process.
Explain why V2O5 can be described as a catalyst in this reaction.
Fe2+(aq) ions catalyse the reaction between iodide and peroxodisulfate ions:
S2O82-(aq) + 2I-(aq) ➔ 2SO42-(aq) + I2(aq)
Explain what type of catalysis is occuring this reaction.
Give two equations to describe how Fe2+(aq) ions act as a catalyst in this reaction.
This question is about catalytic converters in car exhaust systems.
When petrol is burnt in a car engine, pollutant gases including carbon monoxide and nitrogen monoxide are formed.
Write the equation for the reaction between these two polluting gases that takes place on the surface of a catalytic converter. State symbols are not required.
Describe the stages by which the reaction in part a) occurs in a catalytic converter.
State why a heterogeneous catalyst is suitable for a reaction in the gas phase.
Explain what is meant by the term transition element.
Draw electrons in the boxes below to show the electronic configurations of Cu, Cu+ and Cu2+.
Complete the table by predicting the appropriate metal ions, co-ordination numbers, formulae and charges for the complexes A-D.
Explain why complexes formed from transition metal ions are coloured.
This diagram represents the energy change that occurs when a d electron in a transition metal ion is excited by visible light.
The energy change shown in the diagram represents the energy of green light and results in a solution that appears violet.
Violet light has a higher frequency than green light.
Suggest how the energy change, ΔE,will differ for a transition metal ion that forms a green solution.
Explain your answer.
State 3 different features of transition metal complexes that cause a change in the value of ΔE.
The complex [Co(NH3)4Cl2]+ shows isomerism.
Suggest the type of isomerism shown in [Co(NH3)4Cl2]+ and draw 3D structures of the two isomers.
The diagram below shows the structure of ethane-1,2-diamine, en.
en is an example of a bidentate ligand.
Explain what is meant by the term bidentate ligand.
Ethanal is oxidised to ethanoic acid by oxygen. The equation for this reaction is:
2CH3CHO + O2 ➔ 2CH3COOH
This redox reaction is slow at room temperature but speeds up in the presence of cobalt compounds.
Explain why a cobalt compound is able to act as a catalyst for this process.
Steel pipelines carrying natural gas can corrode to form ‘green rust’, Fe(OH)2.
After some time, green rust can change into ‘black rust’ via the equation shown below.
3Fe(OH)2 ➔ Fe2+Fe3+2O4 + H2 + 2H2O
Use oxidation states to show that this is a redox reaction.
If seawater is present, the green rust is often oxidised to [FeCl4]- ions.
Draw diagrams to show two possible shapes for [FeCl4]-.
Name the shapes.
State the type of bonding between the chloride ligands and the iron ion in [FeCl4]-.
Cu+ also forms complexes with chloride ligands.
One example is the colourless complex [CuCl2]-.
Explain why [CuCl2]- ions are colourless.
Transition metals have characteristic properties due to their electron arrangements.
Give two characteristic properties of transition metals.
Give the electronic configurations of a chromium atom, a Cr2+ ion and a Cr3+ ion.
Explain why chromium has variable oxidation states.
Ammonium hexachloroplatinate, (NH4)2PtCl6, is a complex of platinum used in platinum plating. Ammonium hexachloroplatinate contains the hexachloroplatinate ion.
Draw a 3D diagram to show the shape of a hexachloroplatinate ion.
On your diagram, show:
- the name of the shape
- the charge on the ion
- the value of the bond angle.
Platin, Pt(NH3)2Cl2, is a neutral complex of platinum(II).
Explain why Pt(NH3)2Cl2 has no overall charge.
Pt(NH3)2Cl2, displays cis-trans isomerism.
Draw the structure of cis-platin. State its shape and give a value of the Cl-Pt-Cl bond angle.
The use of cis-platin can cause side effects so oxaliplatin has been developed.
The structure of oxaliplatin is shown below.
Draw the structures of the two bidentate ligands in oxaliplatin.
This question look at the ions and complexes of cobalt.
An octahedral complex ion Y, C9H30N6Co3+, exists as two optical isomers.
In complex ion Y, Co3+ is bonded to three molecules of a bidentate ligand L.
Write the molecular formula of the bidentate ligand L.
The diagram below shows the skeletal formula of L.
Explain how L is able to act as a bidentate ligand.
Draw a diagram that shows the shape of the complex ion Y and shows the type of bond between the ligand L and the cobalt.
The compounds [Co(NH3)5Br]SO4 and [Co(NH3)5SO4]Br are structural isomers.
Define the term structural isomer.
What is the oxidation number of cobalt in [Co(NH3)5Br]2+?
Some transition metals and their compounds act as catalysts. The catalysis can be classified as heterogeneous or homogeneous.
Complete the table below to indicate the type of catalysis in each reaction.
The oxidation of C2O42- ions by MnO4- ions in acidic solution is an example of a reaction that is autocatalysed.
State the meaning of the term autocatalysed.
Write 2 equations to show how the autocatalyst, Mn2+, is involved in this oxidation of C2O42- ions.
When NH3(aq) is added to Cu2+(aq), dropwise at first and then in excess, two chemical reactions occur as shown.
For each reaction:
- describe what you would see
- write an equation.
When complex ion B, [Cu(NH3)4(H2O)2]2+, reacts with 1,2-diaminoethane (en), the ammonia molecules but not the water molecules are replaced.
Write an equation for this reaction.
en = 1,2-diaminoethane.
Suggest why the enthalpy change for the reaction in part b) is approximately zero.
Explain why the reaction in part b) is spontaneous despite having an enthalpy change that is approximately zero.
The equation below represents the dissociation of [Fe(H2O)6]3+ ions in aqueous solution.
[Fe(H2O)6]3+(aq) ⇌ [Fe(H2O)5OH]2+(aq) + H+(aq)
The Ka for this dissociation is 6.00 × 10-3 mol dm-3
Calculate the pH of a 1.50 x 10-2 mol dm-3 solution of [Fe(H2O)6]3+.
Give your answer to 2 decimal places.
The diagram below shows some reactions of iron ions in aqueous solution.
Give the formulae of A and B and state their colours.
The green precipitate A, Fe(OH)2, turned brown on standing in air.
Explain why.
This question looks at the biological applications of transition metal complexes.
Red blood cells contain haemoglobin.
Explain using ligand substitutions:
- how haemoglobin transports oxygen around the body
- why carbon monoxide is toxic.
Cis-platin, Pt(NH3)2Cl2, is an effective anti-cancer drug.
Describe the action of cis-platin in this role.
The use of cis-platin can cause side effects so nedaplatin has been developed.
Nedaplatin can be synthesised from cis-platin, as shown below.
Name the type of reaction that is occuring.
When concentatd hydrochloric acid is added to aqueous Cu2+ ions, the following equilibirum is established.
[Cu(H2O)6]2+ + 4Cl- ⇌ [CuCl4]2- + 6H2O
State the colours of the [Cu(H2O)6]2+ and [CuCl4]2- complex ions.
Draw the shapes of the [Cu(H2O)6]2+ and [CuCl4]2- complex ions.
Give the name of the shape for each ion.
State the coordination numbers of the copper ion in [Cu(H2O)6]2+ and [CuCl4]2-.
Explain the change in coordination number in this equilibrium.
In aqueous solution, the [Cu(H2O)6]2+ ion reacts with an excess of ethane-1,2-diamine (en) to form the complex ion Z.
Write an equation for this reaction.
en = 1,2-diaminoethane
Explain, in terms of the chelate effect, why the complex ion Z is formed in preference to the [Cu(H2O)6]2+ complex ion.
Describe the reactions of [Cr(H2O)6]3+ complex ions with:
- aqueous sodium hydroxide
- excess aqueous ammonia
- hydrochloric acid In your answer you should link observations with ionic equations.
Describe the reactions of [Cu(H2O)6]2+ complex ions with:
- aqueous sodium hydroxide
- excess concentrated aqueous ammonia
- excess concentrated hydrochloric acid In your answer you should link observations with ionic equations.
Compound X is a green solid containing one cation and one anion. It dissolves in water to form a green solution.
Give the formula of two cations which could be responsible for the green colour in the solid.
A student adds dilute sodium hydroxide solution, drop by drop, to an aqueous solution of X.
A green precipitate forms, which dissolves in excess sodium hydroxide solution to form a dark green solution.
Give the formula of the cation in X.
Give a formula for the green precipitate.
Give a formula for the species present in the dark green solution.
The student adds a few drops of acidified potassium mangantate(VII) solution to another sample of a solution of X in a test tube.
State the colour change that occurs.
This question is about transition metal chemistry.
The amphoteric character of solid chromium(III) hydroxide is shown by the fact that it reacts separately with both dilute hydrochloric acid and dilute sodium hydroxide solution.
Write an ionic equation for the reaction of solid chromium(III) hydroxide with dilute hydrochloric acid, showing the formula of the complex ion formed.
Include state symbols in your answer.
Describe the changes you would see when the reaction in part a) is carried out.
Write an ionic equation for the reaction of solid chromium(III) hydroxide with dilute sodium hydroxide solution, showing the formula of the complex ion formed.
Include state symbols in your answer.
State the final appearance of the reaction mixture in part c).
The inorganic compounds A, B and C each contain one cation and one anion.
A is a green solid.
Two tests were carried out on separate portions of an aqueous solution of A:
- Test 1: A green precipitate formed when a few drops of NaOH(aq) were added to a sample of the solution of A. Upon addition of excess NaOH(aq), the precipitate dissolved to form a green solution.
- Test 2: A white precipitate formed when dilute HNO3(aq) and AgNO3(aq) were added to a sample of the solution of A.
Give the formulae of the cation and anion in A.
Give the formula of the anion responsible for the green colour of the final solution in test 1.
Write the ionic equation for the reaction in test 2. Include state symbols.
B is a pale pink solid.
Two tests were carried out on separate portions of an aqueous solution of B:
- Test 1: A light-brown precipitate formed when when NaOH(aq) was added to a sample of the solution of B. The precipitate darkened on standing in air.
- Test 2: A white precipitate formed when dilute HNO3(aq) and BaCl2(aq) were added to a sample of the solution of B.
Give the formulae of the cation and anion in B.
Identify the precipitate formed in test 1, and explain why it darkens.
Write the ionic equation for the reaction in test 2. Include state symbols.
A compound of a d-block element is dissolved in water to form a solution X.
A series of tests is carried out on separate 1 cm3 portions of solution X.
Complete the table.
Sulfur dioxide is passed through a sample of solution X. A redox reaction occurs in which the sulfur dioxide forms sulfate ions.
The solution Y which forms is no longer yellow-brown.
Excess dilute aqueous ammonia was added to a 1 cm3 solution of Y in a test tube. A precipitate is observed.
State the colour and formula of the precipitate.
State the formula of the cation in solution Y.
The mixture from part b) was left to stand for a few minutes. The surface of the precipitate turned brown.
State the formuala of the brown compound.
Complete the ionic equation for the reaction between the cation in solution X and sulfur dioxide to form solution Y.
State symbols are not required.
.......... + SO2 + 2H2O ➔ .......... + SO42- + ..........
A blue solid was given to a student who suggested, from its colour only, that it was copper(II) sulfate. Another student suggested that it was copper(II) hydroxide, which is also blue. The students proposed some tests to distinguish between these two blue solids.
Give the expected observations for copper(II) sulfate and copper(II) hydroxide.
A flame test was carried out on the blue solid, but the flame colour observed was not that expected for a blue solid containing copper(II) ions.
Therefore another student suggested that the blue solid could be anhydrous cobalt(II) chloride, which can easily be distinguished from copper(II) compounds by the addition of deionised water.
State the expected observation for the addition of deionised water to anhydrous cobalt(II) chloride.
Give the formula of the complex ion formed.
Cobalt(II) chloride can be distinguished from copper(II) sulfate and copper(II) hydroxide by testing for the anion. Describe a suitable test for the chloride ion, including the positive result.