Transition metal catalysts

Nitrogen dioxide gas is formed when magnesium nitrate is heated.

Table 4 shows some thermodynamic data.

Give the standard conditions indicated by the symbol in Δ_f and

Use the equation and the data in Table 4 to calculate the temperature at which this reaction becomes feasible.

Nitrogen dioxide can also be produced in a reaction between ammonia and oxygen.

Table 5 shows some bond enthalpy values.

Assume that the bonds between N and O in NO₂ are the same.

Calculate the mean bond enthalpy, in kJ mol^–1, for a bond between N and O in NO₂

An alloy of platinum and rhodium is used as a catalyst in the reaction.

What type of catalyst is this?

Some ammonia and oxygen are reacted and the mixture is left to reach equilibrium at a fixed temperature.

Explain why increasing the temperature of this equilibrium mixture decreases the mole fraction of NO₂ in the equilibrium mixture.

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.

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.

Which process does not involve a heterogeneous catalyst?

This question is about catalysis.

Zeolites are used as heterogeneous catalysts in the catalytic cracking of alkanes.

Tetradecane (C₁₄H₃₀) can be cracked to form octane and a cycloalkane.

Give an equation for this reaction.

State the meaning of the term heterogeneous.

Equation

A student determines the concentration of ethanedioate ions in an acidified solution by titration with potassium manganate(VII) solution.

The mixture is warmed before the addition of potassium manganate(VII) solution because the reaction is slow at first. When more potassium manganate(VII) solution is added, the mixture goes colourless quickly due to the presence of an autocatalyst.

Explain the meaning of the term autocatalyst.

Explain, using equations where appropriate, why the reaction is slow at first and then goes quickly.

The reaction between peroxodisulfate ions and iodide ions in aqueous solution can be

Table 6 gives relevant standard electrode potentials.

Use the electrode potential data to suggest how Co²⁺ catalyses the reaction.

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.

This question is about emissions of oxides of nitrogen from petrol and diesel engines.

Explain how oxides of nitrogen are formed in engines.

State why it is desirable to decrease emissions of oxides of nitrogen from vehicles.

Modern diesel vehicles use diesel exhaust fluids, such as AdBlue, to decrease emissions of oxides of nitrogen.

AdBlue reacts with water in the hot exhaust gases to form ammonia. In the presence of a catalyst the ammonia reacts with oxides of nitrogen to form nitrogen and water.

Give the oxidation state of nitrogen in each of NO₂, NH₃ and N₂

Complete the equation for the reaction between NO₂ and NH₃

Oxidation state of nitrogen in

Equation

Petrol vehicles have a catalytic converter which decreases emissions of oxides of nitrogen. Platinum in the catalytic converter acts as a heterogeneous catalyst.

State the meaning of the term heterogeneous catalyst.

Some carbon particulates are also formed in both diesel and petrol vehicles.

Explain why carbon particulates are formed.

This question is about oxides.

Sodium oxide forms a solution with a higher pH than magnesium oxide when equal amounts, in moles, of each oxide are added separately to equal volumes of water.

State why both oxides form alkaline solutions.

Suggest why sodium oxide forms a solution with a higher pH than the solution formed from magnesium oxide.

Give an equation for the reaction between phosphorus(V) oxide and water.

In the Contact process, sulfur(IV) oxide is converted into sulfur(VI) oxide using vanadium(V) oxide as a catalyst.

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

The equation for the reaction between ammonia and oxygen is shown.

Some standard entropies are given in Table 3.

Calculate the entropy change for the reaction between ammonia and oxygen.

Calculate a value for the Gibbs free-energy change (ΔG), in kJ mol^–1, for the reaction between ammonia and oxygen at 600 °C

(If you were unable to obtain an answer to Question 03.1, you should assume that the entropy change is 211 J K^–1 mol^–1. This is not the correct answer.)

The reaction between ammonia and oxygen was carried out at a higher temperature.

Explain how this change affects the value of Δ G for the reaction.

Platinum acts as a heterogeneous catalyst in the reaction between ammonia and oxygen. It provides an alternative reaction route with a lower activation energy.

Deduce the change in oxidation state of nitrogen, when NH₃ is oxidised to NO

When ammonia reacts with oxygen, nitrous oxide (N₂O) can be produced instead of NO

Give an equation for this reaction.

This question is about vanadium compounds and ions.

Use data from Table 4 to identify the species that can be used to reduce VO₂⁺ ions to VO²⁺ in aqueous solution and no further. Explain your answer.

Give the oxidation state of vanadium in [VO(H₂O)₅]²⁺

The [V(H₂O)₄Cl₂]⁺ ion exists as two isomers. One isomer is shown.

Draw the structure of the other isomer and state the type of isomerism.

Type of isomerism

Heating NH₄VO₃ produces vanadium(V) oxide, water and one other product.

Give an equation for the reaction.

Vanadium(V) oxide is the catalyst used in the manufacture of sulfur trioxide.

Give two equations to show how the catalyst is used and regenerated.

Which ion cannot catalyse the reaction between iodide (I^–) and peroxodisulfate (S₂O₈^2–)?

Use the data below to help you answer this question.