Catalysts

Hydrogen peroxide decomposes to form water and oxygen.

This decomposition is shown in the equation.

Give the test for oxygen gas.

The rate of reaction is increased by adding a suitable catalyst.

Describe how a catalyst increases the rate of a reaction.

A student uses this apparatus to investigate the rate of decomposition of hydrogen peroxide solution.

The student adds 100 cm³ of hydrogen peroxide solution at 20 °C to the apparatus labelled A.

The student records the volume of oxygen gas collected every minute for 16 minutes.

The graph shows the student’s results.

Name the pieces of apparatus labelled A and B.

Determine the volume of oxygen gas produced in the first 4 minutes.

Show on the graph how you obtain your answer.

Determine the rate of reaction at 8 minutes by drawing a suitable tangent to the curve.

Include the units for the rate of reaction.

This is the equation for the decomposition of hydrogen peroxide.

The rate of reaction increases when a catalyst of manganese(IV) oxide is added.

Describe how a catalyst increases the rate of a reaction.

A student adds 50 cm³ of hydrogen peroxide solution to a glass container and then adds 1.0 g of manganese(IV) oxide.

The diagram shows the apparatus the student uses.

Name the glass container the student uses.

The student waits until the hydrogen peroxide solution completely decomposes.

Describe how the student could then show that the manganese(IV) oxide was a catalyst and not a reactant.

A student uses this apparatus to investigate the decomposition of hydrogen peroxide solution.

This is the equation for the reaction.

Give the test for oxygen.

Complete the dot‑and‑cross diagram for a molecule of hydrogen peroxide.

Show outer electrons only.

H O O H

The student measures the volume of oxygen collected at regular intervals until the reaction stops.

The table shows the student’s results.

Plot the student’s results on the grid.

Draw a curve of best fit.

Explain in terms of particle collision theory how decreasing the concentration affects the rate of a reaction.

The student repeats the experiment using the same volume of hydrogen peroxide solution but with half the original concentration.

All other conditions are kept the same.

On the grid, draw the curve you would expect the student to obtain.

In this reaction, the manganese(IV) oxide acts as a catalyst.

Explain how a catalyst works.

A student uses this apparatus to investigate the rate of reaction when hydrogen peroxide solution decomposes.

This is the equation for the reaction.

Give a reason why the gas that collects in the gas syringe is not pure oxygen.

The rate of reaction can be increased by adding a catalyst to the hydrogen peroxide solution.

Describe how a catalyst increases the rate of a reaction.

These solids catalyse the decomposition of hydrogen peroxide solution.

• lead(IV) oxide

• manganese(IV) oxide

Describe a method that the student could use to find out which solid is the more effective catalyst.

A student investigates the decomposition of a solution of hydrogen peroxide at different temperatures.

The graph shows how the total volume of oxygen collected in the syringe changes with time when the solution is at a temperature of 20 °C.

On the grid, draw the curve the student would obtain at a temperature of 40 °C when all other conditions are kept the same.

Zinc reacts with dilute hydrochloric acid to form zinc chloride and hydrogen gas.

This is the equation for the reaction.

In an experiment, 20 cm³ of hydrochloric acid containing 0.0036 mol are reacted with 1.3 g of zinc granules at a temperature of 30 °C.

Show by calculation that the zinc is in excess.

The volume of hydrogen collected is measured at regular time intervals.

Curve A shows the results of this experiment.

The experiment is repeated using 1.3 g of zinc powder instead of zinc granules.

All other conditions are kept the same.

On the grid, draw the curve you would expect to obtain.

In the original experiment, 20 cm³ of hydrochloric acid containing 0.0036 mol were reacted with 1.3 g of zinc granules at a temperature of 30 °C and curve A was obtained.

The student does two more experiments and obtains curves B and C.

In one of these experiments the student repeats the original method but at a temperature of 20 °C.

Explain in terms of particle collision theory why the curve obtained could be curve B.

In the other experiment the student repeats the original method but uses 20 cm³ of hydrochloric acid containing 0.0018 mol.

Explain why curve C shows the results the student obtained.

Catalysts can be used to speed up reactions.

Describe how a catalyst works.

When ethanoic acid reacts with ethanol in the presence of concentrated sulfuric acid, one of the products is ester A.

This is the equation for the reaction.

ethanoic acid
ethanol
water

Draw a circle around the functional group in ethanoic acid.

Give the displayed formula of ester A.

Name ester A.

The reaction mixture is kept in a sealed container until dynamic equilibrium is reached.

State what is meant by the term dynamic equilibrium.

During the reaction, the number of moles of ethanoic acid in the reaction mixture decreases, but the number of moles of concentrated sulfuric acid does not change.

Give a reason why the number of moles of concentrated sulfuric acid does not change.

A student does a titration to find the accurate volume of sodium hydroxide solution needed for complete neutralisation.

The student starts by using a pipette to transfer 25.0 cm³ of the reaction mixture to a conical flask.

Describe how the student should complete the titration.

This question is about rates of reaction.

A student uses this method to investigate the rate of reaction between iron(III) nitrate solution and sodium thiosulfate solution.

• pour 50 cm³ of iron(III) nitrate solution into a conical flask

• add one drop of catalyst solution

• add 50 cm³ of sodium thiosulfate solution to the conical flask

• record the time for the mixture to become colourless

The student repeats the method using different catalysts and also with no catalyst.

The table shows the student’s results.

Explain which is the best catalyst for the reaction.

Explain how a catalyst increases the rate of a reaction.

The rate of a reaction can also be altered by changing the temperature or by changing the concentration of solutions.

Explain, using the particle collision theory, how increasing the temperature affects the rate of a reaction.

Explain why using a solution of a lower concentration decreases the rate of reaction.

In the presence of an iron catalyst, nitrogen reacts with hydrogen to form ammonia.

The reaction conditions used are a temperature of 450C and a pressure of 200 atmospheres.

This is the equation for the reaction.

State what the symbol represents.

Give the reason for using a catalyst.

The reaction mixture is kept at a pressure of 200 atmospheres, but the

Explain the effect of this change on the yield of ammonia at equilibrium.

The reaction mixture is kept at a temperature of 450C, but the pressure is increased to 300 atmospheres.

Explain the effect of this change on the yield of ammonia at equilibrium.

Draw an energy level diagram for the reaction between nitrogen and hydrogen.

Include the reactants, products and Δ H in your diagram.

QUESTION 7 CONTINUES ON NEXT PAGE

At the start of the reaction, 48 dm³ of nitrogen is added to 120 dm³ of hydrogen at rtp.

[molar volume of any gas at rtp = 24 dm³]

Show by calculation that the nitrogen is in excess.

The yield of ammonia at equilibrium is 20 %.

Calculate the volume, in dm³, of ammonia formed from 120 dm³ of hydrogen.

Hydrogen peroxide solution decomposes to give water and oxygen gas.

The equation for this reaction is

Three different solids are catalysts for the decomposition of hydrogen peroxide solution.

A student is given hydrogen peroxide solution and a sample of each of the solid catalysts.

The student has a timer, a measuring cylinder, a balance and the apparatus shown in the diagram.

Describe a method the student could use to find which of the three solids is the most effective catalyst for the decomposition of hydrogen peroxide solution.

The diagram shows the reaction profile for the decomposition of hydrogen peroxide without a catalyst.

Label the diagram to show the activation energy (E_a) and the enthalpy change (Δ H) for this reaction.

On the diagram, draw a curve to show the reaction profile for the same reaction when a catalyst is used.

This question is about three stages in the manufacture of sulfuric acid.

In stage 1, sulfur is burned in oxygen to form sulfur dioxide gas.

State one environmental problem caused by the release of sulfur dioxide into the atmosphere.

A mass of 6.4 tonnes of sulfur is burned to produce sulfur dioxide gas.

Calculate the maximum volume, in dm³, of sulfur dioxide gas that can be produced at rtp.

[molar volume of sulfur dioxide gas at rtp = 24 dm³]

[1 tonne = 10⁶g]

Give your answer in standard form.

In stage 2, sulfur dioxide is reacted with oxygen to form sulfur trioxide gas.

The yield of sulfur trioxide is approximately 98%.

A catalyst is used in this reaction.

Explain how a catalyst increases the rate of a reaction.

The temperature is kept constant.

Give a reason why increasing the pressure would increase the yield of sulfur trioxide.

Suggest why it is not necessary to increase the pressure in stage 2.

In stage 3, the sulfur trioxide is reacted with concentrated sulfuric acid to form a liquid called oleum, H₂S₂O₇

The oleum is then added to water to form concentrated sulfuric acid.

Complete the chemical equations for these two reactions.

Sulfuric acid reacts with ammonia to form ammonium sulfate, (NH₄)₂SO₄

Calculate the percentage by mass of nitrogen in ammonium sulfate.

[M_r of (NH₄)₂SO₄ = 132]

Hydrogen peroxide solution decomposes slowly at room temperature to form water and oxygen.

The equation for the reaction is

A catalyst increases the rate of this reaction.

State one other property of a catalyst.

A student has samples of three solids, X, Y and Z.

The student uses this apparatus to find out which solids act as catalysts in the decomposition of hydrogen peroxide solution.

Describe the method that the student should use to find out which solids act as catalysts.

The decomposition of hydrogen peroxide solution is exothermic.

On the diagram, draw and label the reaction profiles for the reaction

without a catalyst

with a catalyst

The equation for the reaction can be shown using displayed formulae.

The table gives the bond energies for two of the bonds.

Use this information to calculate the total amount of energy needed to break all the bonds in two moles of H₂O₂

Use this information to calculate the total amount of energy released when all the bonds in two moles of H₂O are formed.

Use the value of ΔH and your answers for (i) and (ii) to calculate the bond energy, in kJ/mol, for the O O bond.

bond energy =_........ kJ/mol

A solution of hydrogen peroxide decomposes when a catalyst of manganese(IV) oxide is added.

The products of the reaction are water and oxygen.

Complete the chemical equation for this reaction.

Give a test for oxygen.

State the reason for adding a catalyst.

A student investigates how changing the concentration of the hydrogen peroxide solution affects the rate of this reaction.

She uses this apparatus.

The student records the volume of oxygen that collects every 2 minutes for 16 minutes.

The table shows her results.

Plot the student’s results on the grid.

Draw a circle on the grid around the anomalous result.

Draw a curve of best fit through the points, ignoring the anomalous result.

Suggest a mistake that the student might have made to cause the anomalous result.

Determine the volume of oxygen collected during the first 3 minutes.

Show on your graph how you obtain your answer.

The student repeats the experiment using hydrogen peroxide solution of half the concentration of the original solution.

She keeps the volume of the hydrogen peroxide solution and all other conditions the same.

Draw on the grid the curve you would expect the student to obtain.

Explain how using hydrogen peroxide solution of half the concentration affects the rate of the reaction.

Refer to particle collision theory in your answer.

Complete the chemical equation for the reaction in stage 1.

Give the meaning of the symbol

State the purpose of the platinum catalyst.

Give a chemical equation for the reaction of nitrogen monoxide and oxygen in stage 2.

The equation for the reaction in stage 3 is

Calculate the maximum mass, in tonnes, of nitric acid that could be produced in this reaction from 11.5 tonnes of nitrogen dioxide.

mass of nitric acid =_........ tonnes

Suggest what use can be made of the nitrogen monoxide gas formed in stage 3.

When copper(II) oxide reacts with dilute nitric acid, copper(II) nitrate is produced.

The equation for the reaction is

0.200 mol of nitric acid reacts with excess copper(II) oxide.

A mass of 15.3 g of copper(II) nitrate is produced.

Calculate the percentage yield of copper(II) nitrate.

[M_r of copper(II) nitrate = 187.5]

Oxygen can be prepared from hydrogen peroxide using a catalyst.

Which is a correct statement about oxygen?

Explain how a catalyst increases the rate of a reaction.

The equation for the preparation of oxygen from hydrogen peroxide is

This equation can also be written using displayed formulae to show all the covalent bonds in the molecules.

The table gives the bond energies for these bonds.

Use the values in the table to calculate the enthalpy change, Δ H, for the reaction.

Include a sign in your answer.

Complete the energy level diagram to show the position of the products and the enthalpy change, Δ H, for the reaction.

This question is about ethane and ethene.

Ethane can be obtained from crude oil.

Describe the industrial process used to separate crude oil into fractions.

The equation for the reaction between ethene gas and hydrogen gas is

The rate of this reaction can be increased by increasing the pressure.

Explain why increasing the pressure increases the rate of this reaction.

The rate of this reaction can also be increased by using a catalyst.

Explain how using a catalyst increases the rate of a reaction.

Give one other way that the rate of reaction between ethene gas and hydrogen gas can be increased.

The reaction between ethene and hydrogen is exothermic.

Complete the reaction profile diagram, including labels for the activation energy and the enthalpy change, H.

The reaction between ethene and hydrogen can be represented using displayed formulae.

H H H H

Use the bond energies in the table to calculate the enthalpy change, H, in kJ/mol for this reaction.

H =_........ kJ/mol