Metal-aqua ions in solution

This question is about the chemistry of copper.

Deduce the number of unpaired electrons in a Cu²⁺ ion.

Describe how water acts as a ligand in the formation of [Cu(H₂O)₆]²⁺

A solution of sodium carbonate is added to a blue solution containing

State what is observed.

Give an equation for the reaction.

Equation

When a solution containing [Cu(H₂O)₆]²⁺ ions reacts with an excess of concentrated hydrochloric acid, a ligand exchange reaction occurs.

Blue Yellow

The shape and the colour of the [CuCl₄]^2– ion are different from the shape and the

Explain

• the shape of each complex ion and why these shapes are different

• how colour arises in complex ions

• why the [CuCl₄]^2– ion has a yellow colour, different from the blue colour of the

An excess of water, followed by an excess of concentrated aqueous ammonia, is added to a solution containing [CuCl₄]^2– ions.

State what is observed.

Give an equation for the overall change that occurs.

Equation

A solution contains M₂[Cu(C₂O₄)₂(H₂O)₂] where M is a metal.

A student does a titration to determine the identity of M.

• 2.52 g of solid M₂[Cu(C₂O₄)₂(H₂O)₂] are dissolved in dilute sulfuric acid.

• This solution is transferred to a volumetric flask and made up to 250 cm³ with dilute sulfuric acid.

• A 25.0 cm³ portion is pipetted into a conical flask.

• The mixture in the conical flask is heated to 60 °C and then titrated with 0.0200 mol dm^–3 KMnO₄ solution.

• Several titrations are done and the student’s results are shown in Table 3.

In this titration, only the C₂O₄^2– ions react with the MnO₄^– ions. 2 mol of MnO₄^– ions react with 5 mol of C₂O₄^2– ions.

Give an equation for the reaction between C₂O₄^2– ions and MnO₄^– ions in acidic solution.

Calculate the mean titre from the student’s results.

Calculate the M_r of M₂[Cu(C₂O₄)₂(H₂O)₂]

Identify M.

Draw the structure of two stereoisomers of the complex ion in M₂[Cu(C₂O₄)₂(H₂O)₂] and include the charge on each structure.

Structure 1
Structure 2

This question is about vanadium and some of its compounds.

State the block in the Periodic Table that contains vanadium.

Suggest why vanadium can be pulled into thin wires.

Vanadium(V) oxide is a catalyst in the Contact process.

Give two equations to show how vanadium(V) oxide acts as a catalyst in this process.

Equation 1

Equation 2

Table 6 shows some electrode half-equations and their standard electrode potentials.

Sn reduces VO₂⁺ in acidic solution.

Use the data in Table 6 to deduce an overall equation for the reaction that occurs.

Vanadium(III) sulfate is a pale yellow solid at room temperature.

Explain why vanadium(III) sulfate has a high melting point.

When vanadium(III) sulfate dissolves in water, the vanadium-containing species formed is acidic.

Give an equation to show how vanadium(III) sulfate dissolves in water to form the acidic vanadium-containing species.

Explain why the vanadium-containing species is acidic.

Equation

Compound Q is found in crude oil and has the molecular formula C₃₃H₃₄N₄VO₄

A sample of Q is ionised by electrospray ionisation in a time of flight (TOF) mass spectrometer. The spectrum produced shows that the

Give an equation to show how Q is ionised using electrospray ionisation.

Determine the m / z value of the molecular ion formed in this ionisation process.

Equation

A sample of vanadium contains only⁴⁹V and⁵¹V

The relative atomic mass of vanadium in this sample is 50.97

Calculate the percentage abundance of⁵¹V in this sample.

Which reaction produces an octahedral complex ion ?

This question is about aqueous ions of the metal iron.

When an aqueous [Fe(H₂O)₆]³⁺ ion reacts with ethanedioate ions, an iron(III) complex ion X is formed.

The only ligands in X are ethanedioate ions.

Draw the structure of X.

Include the charge.

The formation of X is an example of the chelate effect.

Explain the meaning of the chelate effect.

Outline how Fe²⁺ ions catalyse the reaction between S₂O₈^2– ions and I^– ions in aqueous solution.

In your answer you should include

• a sketch graph to show how the concentration of S₂O₈^2– ions changes over time

• an explanation of how Fe²⁺ ions catalyse the reaction, including equations

• an overall equation for the reaction.

A student adds dilute ammonia solution to a solution containing [Fe(H₂O)₆]²⁺ ions.

Give the formula of the precipitate that forms.

The student adds sodium carbonate solution to a solution containing

State one observation the student would make.

Give an equation for the reaction.

Equation

A solution containing [Fe(H₂O)₆]²⁺ ions changes to a yellow-brown colour after several hours in contact with air.

The student adds sodium carbonate to the yellow-brown solution.

Give an equation for the reaction with sodium carbonate.

Aqueous aluminium sulfate is added to aqueous sodium carbonate.

What are the formulas of the precipitate and the gas formed?

This question is about complexes containing the aluminium ion.

Give the electron configuration of the Al³⁺ ion.

When anhydrous aluminium sulfate, Al₂(SO₄)₃, is added to water a solution forms that contains the complex aluminium ion, [Al(H₂O)₆]³⁺

Give the equation for the reaction.

Explain why the solution containing [Al(H₂O)₆]³⁺ is acidic.

State why the concentration of aluminium sulfate solution can not be determined by

An excess of aqueous ammonia is added to a solution containing [Al(H₂O)₆]³⁺

Give an ionic equation for the reaction and state one observation.

Equation

An excess of dilute sulfuric acid is added to the products of the reaction in Question 07.5

Identify the aluminium species produced.

Figure 3 shows the structure of the EDTA^4– ion.

Atoms of two different elements in EDTA^4– can form co-ordinate bonds with an aluminium ion.

On Figure 3, draw circles around the atoms of two different elements that would link to an aluminium ion by a co-ordinate bond.

Hydrated aluminium sulfate, Al₂(SO₄)₃.xH₂O, is soluble in water.

The relative formula mass and value of x can be found from a titration experiment.

Aqueous [Al(H₂O)₆]³⁺ ions react to form a stable complex when treated with an excess

The excess of EDTA^4– ions is determined by titration with ZnSO₄ solution.

• Dissolve 1.036 g of Al₂(SO₄)₃.xH₂O in distilled water and make up to 250 cm³

• Add 25.0 cm³ of this solution to 50.0 cm³ of a solution containing EDTA^4– ions of concentration 0.0100 mol dm^–3

• Determine the excess of EDTA^4– ions by titrating with ZnSO₄ solution in the presence of an indicator.

The excess of EDTA^4– ions requires 18.00 cm³ of 0.0105 mol dm^–3 ZnSO₄ solution to

The equations for the reactions are

Use the information given to calculate the M_r of Al₂(SO₄)₃.xH₂O

Give your answer as an integer.

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A student is given two aqueous solutions, L and M, that both contain iron salts.

The student does a series of tests on the solutions.

Table 1 shows these tests and the observations.

Identify L and M using the results in Table 1.

In your answer:

• identify all precipitates

• explain why effervescence is seen in the reaction of sodium carbonate with L but not with M

• give ionic equations for all reactions.

Tschermigite is a hydrated, water-soluble mineral, with relative formula mass of 453.2

The formula of tschermigite can be represented as M.xH₂O, where M represents all the ions present.

Table 4 shows its composition by mass.

In an analysis, it is found that the mineral contains the ions NH₄⁺, Al³⁺ and SO₄²

Calculate the empirical formula of tschermigite and the value of x in M.xH₂O

Describe the tests, with their results, including ionic equations, that would confirm the identities of the ions present.

This question is about iron and its ions.

Discuss the role of iron as a heterogeneous catalyst in the Haber process.

Your answer should include:

• the meaning of the term heterogeneous catalyst

• how iron acts as a heterogeneous catalyst

• the factors that affect the efficiency and lifetime of the catalyst.

Fe²⁺ ions catalyse the reaction between peroxodisulfate(VI) ions and iodide ions in aqueous solution.

Explain why this reaction is slow before the catalyst is added. Give two equations to show how Fe²⁺ ions catalyse this reaction.

Why reaction is slow before catalyst added

Equation 1

Equation 2

Give a reason why Zn²⁺ ions do not catalyse the reaction in Question 04.2.

Iron reacts with dilute hydrochloric acid to form iron(II) chloride and hydrogen.

A 0.998 g sample of pure iron is added to 30.0 cm³ of 1.00 mol dm^–3 hydrochloric acid.

One of these reagents is in excess and the other reagent limits the amount of hydrogen produced in the reaction.

Calculate the maximum volume, in m³, of hydrogen gas produced at 30^oC and 100 kPa.

Give your answer to 3 significant figures.

In your answer you should identify the limiting reagent in the reaction.

The gas constant, R = 8.31 J K⁻¹ mol⁻¹

Figure 2 shows some reactions of iron ions in aqueous solution.

Identify A and state its colour.

Give the formula of B and state its colour.

Give an ionic equation for the reaction of [Fe(H₂O)₆]³⁺ with aqueous Na₂CO₃ to form B.

Ionic equation

Explain why an aqueous solution containing [Fe(H₂O)₆]³⁺ ions has a lower pH than an aqueous solution containing [Fe(H₂O)₆]²⁺ ions.

Some reactions of the [Al(H₂O)₆]³⁺(aq) ion are shown.

Give the formula of the white precipitate B.

State one other observation when Na₂CO₃(aq) is added to a solution containing

Give an equation for this reaction.

Equation

Give the formula of the complex ion C.

State one condition needed for the formation of C from [Al(H₂O)₆]³⁺(aq) and NaOH(aq).

Give an equation for this reaction.

Equation

Deduce the formula of the complex ion A.

Explain, with the use of an equation, why a solution containing [Al(H₂O)₆]³⁺ has a pH ˂7

Equation

Figure 3 shows some reactions of aqueous iron ions.

Give the formula of Precipitate J and state its colour. Give an equation for Reaction 1.

Equation

Give the formula of L and an equation for Reaction 2.

Equation

Suggest a reagent for Reaction 3.

Give the formula of Precipitate M and state its colour.

Transition metal complexes have different shapes and many show isomerism.

Describe the different shapes of complexes and show how they lead to different types of isomerism. Use examples of complexes of cobalt(II) and platinum(II).

You should draw the structures of the examples chosen.

When anhydrous aluminium chloride reacts with water, solution Y is formed that contains a complex aluminium ion, Z, and chloride ions.

Give an equation for this reaction.

Give an equation to show how the complex ion Z can act as a Brønsted–Lowry acid with water.

Describe two observations you would make when an excess of sodium carbonate solution is added to solution Y. Give an equation for the reaction. In your equation, include the formula of each complex aluminium species.

Equation

Aqueous potassium hydroxide is added, until in excess, to solution Y.

Describe two observations you would make. For each observation give an equation for the reaction that occurs. In your equations, include the formula of each complex aluminium species.

Equation 1

Equation 2