Transition metals

This question is about reactions of compounds of iron and copper.

Complete the electron configuration of

an Fe atom: 1s²........

a Cu²⁺ ion: 1s²........

Solutions of iron(II) sulfate, FeSO₄, and copper(II) sulfate, CuSO₄, can be distinguished by adding aqueous sodium hydroxide.

Describe what would be observed when NaOH(aq) is added to each solution.

Observation with FeSO₄(aq)........

Observation with CuSO₄(aq)........

The cyclic organic compound pyridine, C₅H₅N, can act as a monodentate ligand.

The structure of pyridine is shown below.

What is meant by a monodentate ligand ?

Aqueous copper(II) sulfate reacts with salicylic acid to form a complex ion which has two stereoisomers.

One isomer of the complex ion is shown:

Draw the other stereoisomer of the complex.

Identify the type of stereoisomerism shown by the complexes.

Type of stereoisomerism........

Calculate the percentage by mass of CuSO₄•5H₂O in Mixture A.

Give your answer to 3 significant figures.

Percentage of CuSO₄•5H₂O in Mixture A =........ %

The student repeats their method, but after carrying out Step 1 they leave the solution exposed to the air for a few days. Some of the iron(II) sulfate is oxidised to iron(III) sulfate.

The student then continues with Step 2, Step 3 and Step 4 of the method.

This mean titre is greater than 31.15 cm³.

Suggest why this mean titre is greater than 31.15 cm³.

This question is about transition elements.

Suggest the formulae of A, B and C.

Complex ion A:........

Solid B:........

Complex ion C:........

Cobalt (III) forms an octahedral complex ion D, which contains both ammonia and chloride ligands.

Complex ion D has a molar mass of 197.9 g mol^–1.

Determine the formula and charge of complex ion D.

Red blood cells contain haemoglobin which transports oxygen around the body.

For efficient transportation of oxygen, healthy human blood must be maintained at a pH value between 7.35 and 7.45.

Human blood acts as a buffer due to the presence of carbonic acid, H₂CO₃, and hydrogencarbonate, HCO₃^–, ions as shown below.

• Explain, using ligand substitution, how haemoglobin transports oxygen around the body.

• Determine whether a sample of blood with a [HCO₃^–]: [H₂CO₃] ratio of 8.5:1 is healthy.

This question is about the d-block elements in Period 4 of the periodic table (Sc to Zn).

* Explain, with examples from Period 4, what is meant by the terms d-block element and transition element.

Explain why some d-block elements are not transition elements.

Use electron configurations to support your explanations.

Describe precipitation reactions using either copper or chromium ions as examples.

Include equations.

Describe ligand substitution reactions using either copper or chromium ions as examples.

Include equations.

The ethanedioate ion, C₂O₄^2–, is a bidentate ligand.

A complex ion of cobalt(III) contains two ethanedioate ligands and two water ligands.

Determine the charge of this complex ion and the coordination number of cobalt in the complex ion.

Charge of complex ion........

Coordination number of cobalt........

An acidified solution containing Cr₂O₇^2– ions reacts with vanadium(III) ions in a redox reaction to form a solution containing Cr³⁺ ions and VO₂⁺ ions.

Construct the overall equation for this reaction.

The three elements that, when in a molecule, can form hydrogen bonds with other suitable molecules.

An element that is a solid at RTP with a simple molecular lattice structure.

The two elements with atoms containing five unpaired electrons.

The element in Period 3 that exists in the solid state as a network of atoms bonded by strong covalent bonds.

The p-block element in Period 3 that forms a compound with fluorine with octahedral molecules.

The element that forms 1– ions most readily.

The element with an average atomic mass of 1.244 10^–22 g.

Which ion(s) contain(s) one or more unpaired electrons?

1 Mn³⁺

2 V³⁺

3 Cu +

A 1, 2 and 3

B Only 1 and 2

C Only 2 and 3

D Only 1

Your answer

This question is about d-block elements.

Most d-block elements are also classified as transition elements.

Explain why scandium and zinc are classified as d-block elements but are not also transition elements.

Your explanations should include full electron configurations.

What is meant by a bidentate ligand ?

* Determine the formulae of A and B. Write the ionic equation for the ligand substitution and show 3D structures for the three stereoisomers of B.

Which property/properties is/are correct for a transition element?

1 The element has atoms with a partially filled d sub-shell.

2 The existence of more than one oxidation state in its compounds.

3 The formation of coloured ions.

A 1, 2 and 3

B Only 1 and 2

C Only 2 and 3

D Only 1

Your answer

This question is about reactions of ions and compounds of transition elements.

A student carries out two experiments on a solution containing [Cr(H₂O)₆]³⁺(aq).

Experiment 1 The student adds an excess of aqueous ammonia to a solution containing [Cr(H₂O)₆]³⁺ until a purple solution is formed.

Experiment 2 The student carries out the following reaction sequence.

Step 1 NaOH(aq) is added slowly to a solution containing [Cr(H₂O)₆]³⁺(aq) in a boiling tube. A grey–green precipitate forms.

Step 2 An excess of NaOH(aq) is added to the boiling tube. The precipitate dissolves and a green solution forms containing a 6 coordinate complex ion.

Step 3 H₂O₂ is added to the mixture and the boiling tube is heated. A yellow solution forms.

Step 4 The solution in the boiling tube is acidified. The solution now contains Cr₂O₇²⁻(aq).

What is the formula of the complex ion in the purple solution that forms in Experiment 1

Suggest an equation for the reaction in Experiment 2, Step 1. Include state symbols.

Draw a 3-D diagram for the shape of the complex ion that forms in Experiment 2, Step 2 Include the charge of the ion.

What is the formula of the ion that causes the yellow colour in Experiment 2, Step 3

State the colour of the solution that forms in Experiment 2, Step 4.

Vanadium ions have four common oxidation states. Table 18.1 shows the colours of the ions in aqueous solution.

Complete the electron configuration of a V³⁺ ion.

The student adds excess iron to a solution containing VO²⁺(aq) ions, and observes that the colour of the solution changes from blue to green and then to violet.

Use the relevant standard electrode potentials shown in Table 18.2 to explain these observations.

Construct an equation for the first colour change from blue to green.

Iron(II) gluconate, C₁₂H₂₂FeO₁₄, is the active ingredient in some brands of iron supplements.

A student carries out an experiment to determine the mass of iron(II) gluconate in one tablet of an iron supplement, using the method below.

Stage 1 The student crushes two tablets and dissolves the powdered tablets in dilute sulfuric acid.

Stage 2 The student makes up the solution from Stage 1 to 250.0 cm³ in a volumetric flask.

Stage 3 The student then titrates 25.0 cm³ portions of the solution obtained in Stage 2 with 0.00200 mol dm⁻³ potassium manganate(VII).

The student obtains a mean titre of 13.50 cm³.

In this titration, 1 mol of manganate(VII) ions reacts with 5 mol of iron(II) ions.

Explain why the student used 0.00200 mol dm⁻³ potassium manganate(VII) solution for this titration, rather than the more usual concentration of 0.0200 mol dm⁻³ used in manganate(VII) titrations.

Use the student’s results to determine the mass, in mg, of iron(II) gluconate in one tablet.

Give your answer to 3 significant figures.

This question is about some reactions of d block elements and their ions.

Table 21.1 shows standard electrode potentials which will be needed within this question.

Complete the electron configuration of

a Ni atom: 1s²........

a Ni²⁺ ion: 1s²........

A standard cell is set up in the laboratory with the cell reaction shown below.

Draw a labelled diagram to show how this cell could be set up to measure its standard cell potential.

Include details of apparatus, solutions and the standard conditions required.

Standard conditions........

Predict the standard cell potential of this cell.

Use the information in Table 21.1 to help you answer both parts of this question.

Write the overall equation for the oxidation of Fe²⁺ by acidified H₂O₂.

Zinc reacts with acidified Cr₂O₇^2– ions to form Cr²⁺ ions in two stages.

Explain why this happens in terms of electrode potentials and equilibria.

Include overall equations for the reactions which occur.

* Three different reactions of copper compounds are described below.

Reaction 1: Aqueous copper(II) sulfate reacts with excess aqueous ammonia in a ligand substitution reaction. A deep-blue solution is formed, containing an octahedral complex ion, C, which is a trans isomer.

Reaction 2: Copper(I) oxide reacts with hot dilute sulfuric acid in a disproportionation reaction. A blue solution, D, and a brown solid, E are formed.

Reaction 3: Copper(II) oxide reacts with warm dilute nitric acid in a neutralisation reaction, to form a blue solution. Unreacted copper(II) oxide is filtered off, and the solution is left overnight in an evaporating basin. A hydrated salt, F, crystallises, with the percentage composition by mass: Cu, 26.29%; H, 2.48%; N, 11.59%; O, 59.63%.

Identify C – F by formulae or structures, as appropriate.

Include equations, any changes in oxidation number, and working.

This question looks at reactions of hydrogen peroxide and of cobalt(II) ions.

Aqueous hydrogen peroxide decomposes as shown in equation 2.1.

The reaction is catalysed by manganese(IV) oxide, MnO₂.

A student investigates the decomposition of a hydrogen peroxide solution as outlined below.

• The student adds 50.00 cm³ of H₂O₂(aq) to a conical flask.

• The student adds a small spatula measure of MnO₂ and quickly connects the flask to a gas syringe.

• The student measures the volume of oxygen every 200 seconds.

The student allows the reaction in equation 2.1 to proceed until no more gas is evolved. The volume of O₂ in the syringe is now 55 cm³, measured at RTP.

Calculate the initial concentration of the H₂O₂.

Give your answer to two significant figures.

initial concentration of H₂O₂ =........ mol dm^–3

Hydrogen peroxide can act as an oxidising agent or as a reducing agent.

Some standard electrode potentials are shown below.

Use this information to write an equation for a reaction in which hydrogen peroxide acts as a reducing agent.

Cobalt(II) forms complex ions with water ligands and with chloride ligands.

• With water ligands, cobalt(II) forms a pink octahedral complex ion, [Co(H₂O)₆]²⁺.

• With chloride ligands, cobalt(II) forms a blue tetrahedral complex ion.

A student dissolves cobalt(II) sulfate in water in a boiling tube. A pink solution forms.

Experiment 1 The student places the boiling tube in a water bath at 100 °C. Concentrated hydrochloric acid is added dropwise. The colour of the solution changes from pink to blue.

Experiment 2 The student places the boiling tube from experiment 1 in an ice/water bath at 0 °C. The colour of the solution changes from blue to pink.

Write the equilibrium equation for the reaction that takes place when the colour of the solution changes.

Explain the observations and predict whether the formation of the blue colour is exothermic or endothermic.

This question is about two compounds used in medicine.

Cis-platin, PtCl₂(NH₃)₂, is a complex of platinum which is used in cancer treatment.

What is the oxidation number of platinum in cis-platin?

Cis-platin is prepared in a ligand substitution reaction which takes place in multiple steps.

The equation for the final step forming cis-platin is shown below.

cis-platin

In the box, outline the mechanism for the formation of cis-platin from [PtCl₃(NH₃)]^–. Use curly arrows and lone pairs where appropriate.

cis-platin

Paracetamol is a solid organic compound used in tablets as a painkiller.

Name the functional groups present in paracetamol.