Variable oxidation states of 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.

Which statement(s) about elements in the periodic table is/are correct?

1 The position of an element is determined by its relative atomic mass.

2 The elements in a group have similar chemical properties.

3 Transition elements are used as catalysts in the manufacture of chemicals.

A 1, 2 and 3

B Only 1 and 2

C Only 2 and 3

D Only 1

Your answer

This question is about the analysis of organic compounds.

Determine the R_f value of propan-1-ol.

Show your working.

Write an equation for the alkaline hydrolysis of 1-bromopropane.

Show structures of organic compounds.

A student investigates the alkaline hydrolysis of 1-chloropropane using the same method as for 1-bromopropane.

Predict, with reasons, how the appearance of the reaction mixture in the chromatogram produced after 20 minutes would be different when 1-chloropropane is used instead of 1-bromopropane.

Suggest why propan-1-ol is run alongside the reaction mixture.

Write the formula of the species causing the colours after refluxing with acidified dichromate(VI

Green solution........

Orange solution........

* The student is provided with further information about compounds F– I.

• They all have the molecular formula C₅H₁₀O.

• One of the compounds is alicyclic.

• The other compounds are unbranched.

Use this further information and the student’s observations in Table 5.1 to answer the following.

• How do the observations provide evidence for the possible functional groups in compounds F– I ?

• Suggest a possible structure for each of the compounds F– I.

Show your reasoning.

This question is about reactions of transition metal compounds.

Explain why ethane-1,2-diamine can act as a bidentate ligand.

The iron(III) ion, Fe³⁺, forms a complex ion A with two ethane-1,2-diamine ligands and two chloride ligands.

Complex ion A has cis and trans stereoisomers. One of these stereoisomers exists as optical isomers.

Determine the empirical formula, with charge, of complex ion A and draw the 3-D structures of the three stereoisomers.

Empirical formula with charge........

Structures

Aqueous sodium hydroxide is added to an aqueous solution of iron(II) sulfate. A pale green precipitate forms which turns brown when left to stand in air.

Write an ionic equation for the formation of the pale green precipitate.

* This question is about copper and copper compounds.

Experiment 1 Hydrochloric acid, HCl (aq), is added to an aqueous solution containing [Cu(H₂O)₆]²⁺ complex ions. A yellow-green solution forms containing complex ion B.

Experiment 2 A piece of copper metal is heated with concentrated sulfuric acid. A reaction takes place forming a pale blue solution C and 45 cm³ of a gas D, measured at RTP. The mass of gas D is 0.12 g.

Experiment 3 An excess of copper(II) oxide is heated with dilute nitric acid. The resulting mixture is filtered. The filtrate is a blue solution E. Aqueous potassium iodide, K I (aq), is added to the blue solution E. A white precipitate F and a brown solution G form.

Determine the formulae of B – G. Construct equations for the reactions taking place, include any changes in oxidation number,

and show your working where appropriate.

In Step 1, the student observed that bubbles of gas were produced.

Suggest the formula of the copper(II) compound which reacted with HNO₃ to form the gas, and write a full equation for the reaction.

Formula:........

Equation:........

Write an ionic equation, including state symbols, for the reaction in Step 3.

Suggest a suitable indicator for this titration and state the colour change at the end point in Step 4.

Indicator:........

Colour from........ to........

Determine the percentage, by mass, of copper in the copper ore. Give your answer to an appropriate number of significant figures.

Explain whether the calculated percentage by mass of copper would be higher, lower or the same if the following changes were made to the method.

The potassium iodide was not in excess, in Step 3.

The burette readings were read from the top of the meniscus, in Step 4.

The student then modifies the method in order to obtain a more accurate value for the percentage by mass of copper in the ore. The student decides to use 25.00 g of the copper ore in Step 1.

What further modifications should the student make to produce a more accurate value for the percentage by mass of copper in the ore?

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 reactions of iron compounds.

In the boxes, write the formulae of A and B.

The student thinks that the reaction of iron(II) sulfide with H⁺ / H₂O is a redox reaction.

Explain, with reasons, whether the student is correct.

Write the equation for the reaction of [Fe(H₂O)₆]²⁺(aq) with Cl₂(g).

Construct an equation for the reaction of H₂S(g) with H⁺(aq)/MnO₄⁻(aq).

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.