Amounts of substance in equations

This question is about making the explosive 2-methyl-1,3,5-trinitrobenzene, commonly known as TNT.

TNT can be made by reacting methylbenzene with concentrated nitric acid in the presence of concentrated sulfuric acid.

Give the overall equation for the reaction between methylbenzene and nitric acid.

The yield of TNT in this reaction is 42.5%.

Calculate the mass, in g, of TNT (M_r = 227.0) obtained from

Methylbenzene has density = 0.867 g cm^–3 and M_r = 92.0

In the mechanism for this reaction, concentrated nitric acid reacts with concentrated sulfuric acid to produce the nitronium ion O₂N⁺

Give an equation for the reaction to produce the nitronium ion.

State the role of the nitronium ion in the reaction with methylbenzene.

Outline the mechanism for the reaction of the nitronium ion with methylbenzene to give 2-methyl-1-nitrobenzene.

Equation

Role of nitronium ion

Mechanism

This question is about gas volumes.

Figure 9 shows some of the apparatus needed to determine an experimental value for the M_r of an unknown volatile liquid Y.

A student uses this method to determine an experimental value for the M_r of Y.

1. Record the volume of air in a gas syringe.

2. Collect a sample of Y in a hypodermic syringe.

3. Record the mass of the hypodermic syringe and Y.

4. Push the needle of the hypodermic syringe through the rubber cap on the gas syringe.

5. Inject a small amount of Y into the gas syringe.

6. Remove the hypodermic syringe from the gas syringe.

7. Record the mass of the hypodermic syringe and the remaining Y.

8. Record the volume of gas in the gas syringe.

9. Record the temperature in the oven and the atmospheric pressure.

Use the results to determine an experimental value for the M_r of Y.

The gas constant, R = 8.31 J K^–1 mol^–1

Show your working.

The percentage uncertainty in the volume of Y in the gas syringe is 0.95%

The percentage uncertainty in the temperature is 0.12%

The uncertainty in each balance reading is ± 0.0005 g

Assume that the uncertainty in the value for pressure is negligible.

Calculate the percentage uncertainty in the use of the balance in this experiment.

Use your answer and the percentage uncertainties for volume and temperature to calculate a range of values for the M_r of Y.

(If you were unable to calculate an experimental value for the M_r of Y in Question 08.1, assume it is 141. This is not the correct answer.)

A teacher suggests placing a seal over the needle of the hypodermic syringe after collecting the sample of liquid Y, and then replacing the seal after injecting the liquid into the gas syringe.

Give a reason why the teacher’s suggestion will improve the experiment.

A mixture of methane and propane has a volume of 40 cm³

This mixture needs exactly 170 cm³ of oxygen for complete combustion.

The equations for these reactions are

Calculate the volume

• of methane in the original mixture

• of propane in the original mixture.

All volumes are measured at the same temperature and pressure.

This question is about an experiment to determine the solubility of strontium hydroxide in water at 20 °C

Strontium hydroxide is slightly soluble in water. Strontium hydroxide solution reacts in a similar way to calcium hydroxide solution.

• Some solid strontium hydroxide is added to approximately 1 dm³ of distilled water in a stoppered flask.

• The mixture is kept at 20 °C. Every day, the mixture is checked. If no solid is present in the flask, more solid strontium hydroxide is added.

• On the day when no more solid needs to be added, the flask is opened and the mixture is filtered into another flask and stoppered.

• A 25.0 cm³ sample of the filtrate is transferred to a conical flask with a pipette and a few drops of indicator added.

• This sample is titrated with 0.100 mol dm^–3 hydrochloric acid.

• The titration is repeated several times with further samples of the filtrate. The results are shown in Table 1 on page 8.

Suggest why the solution is kept until no more solid needs to be added.

Suggest why it is important to remove the undissolved strontium hydroxide before the titration.

After the filtration, the solution is stored in a stoppered flask.

Suggest a reason for stoppering the flask.

The diagrams in Figure 2 show the part of a pipette with the graduation line.

Which diagram identifies the pipette that is correctly filled?

Tick (✓) one box.

Figure 2

Solubility can be quoted as ‘g of solute per 100 cm³ of solution’.

Table 1 shows the results of the titrations between strontium hydroxide and hydrochloric acid. These can be used to determine the solubility of strontium hydroxide.

Give the equation for the reaction between strontium hydroxide and hydrochloric acid.

Use the results in Table 1 to calculate the mean titre.

Use the mean titre to calculate the solubility of strontium hydroxide, in g per 100 cm³ of solution, at 20 °C

Equation

This question is about metals and their compounds.

State why the atomic radius of calcium is greater than the atomic radius of magnesium.

Magnesium reacts with steam.

Give an equation, including state symbols, for this reaction.

Similar-sized pieces of barium and magnesium are added to separate 100 cm³ samples of dilute sulfuric acid. In each case the sulfuric acid is in excess.

The barium reacts quickly at first. After a few minutes the reaction stops, even though there is still some unreacted barium in the flask.

The magnesium reacts more slowly than the barium, but the reaction continues until all the magnesium has reacted.

Explain why

• the barium initially reacts more quickly than the magnesium

• the barium reaction stops before all the barium has reacted.

A metal nitrate X(NO₃)₂ completely decomposes when heated.

A 0.832 g sample of X(NO₃)₂ decomposes on heating to produce a total of

Deduce the identity of metal X.

The ideal gas constant, R = 8.31 J K^–1 mol^–1

Identity of metal X

Sodium reacts with aluminium and hydrogen to form solid NaAlH₄

Give an equation for this reaction.

Suggest why NaAlH₄ has a high melting point.

Equation

Give the equation for the reaction between H₃PO₄ and an excess of NaOH

Lithium is an important metal used in cells to power mobile phones.

In a lithium cell, a lithium cobalt oxide electrode and a lithium electrode are used.

Give the equation for the reaction that occurs at the positive electrode.

Commercial electrochemical cells can be rechargeable or non-rechargeable.

State why lithium cells can be recharged.

This question is about hydrocarbons.

Eicosane (C₂₀H₄₂) can be cracked by heating to 700 K in the presence of a catalyst.

The products are

• an aromatic hydrocarbon C₈H₁₀

• an alkane C₆H₁₄

• another alkane.

Complete the equation for this reaction.

Give a suitable catalyst for this reaction.

Figure 2 shows the¹³C NMR spectrum for the aromatic hydrocarbon C₈H₁₀

Which of these is the structure of C₈H₁₀?

Tick (✓) one box.

Cracking can also be done without a catalyst, using a temperature of 1200 K and a pressure of 7000 kPa

State the type of product that is formed in high percentage in this type of cracking.

A sample of butane has a volume of 20 cm³ at room temperature and pressure.

The sample is burned completely in 1350 cm³ of air.

The final mixture is cooled to room temperature and pressure.

Calculate the total volume of gas in the final mixture. Assume that air contains 21% by volume of oxygen.

Natural gas is used in power stations to produce electricity.

Natural gas contains sulfur impurities. Sulfur dioxide forms when these impurities are burned.

State an environmental problem caused by sulfur dioxide.

Give the formula of a compound that is used to help remove sulfur dioxide from the combustion products.

Environmental problem

Formula of compound

The concentration of dilute hydrochloric acid can be found by titration using a standard solution of barium hydroxide.

Calculate the mass, in g, of solid barium hydroxide (M_r = 171.3) needed to prepare 250 cm³ of 0.100 mol dm^–3 barium hydroxide solution.

The mass of barium hydroxide from Question 06.1 is dissolved in a beaker containing

Describe how this solution is used to make 250 cm³ of the 0.100 mol dm^–3 barium hydroxide solution.

Before the first titration, the 25 cm³ pipette is rinsed with a small volume of the 0.100 mol dm^–3 barium hydroxide solution.

State why it is good practice to rinse the pipette in this way.

Hydrochloric acid is added to the burette using a funnel.

State why it is good practice to remove the funnel from the burette before the titration.

In a different experiment, 0.952 g of solid barium hydroxide is used to make 250 cm³ of standard barium hydroxide solution.

25.0 cm³ of this barium hydroxide solution reacts with exactly

Calculate the concentration of the hydrochloric acid.

The uncertainty in the 25.0 cm³ of solution from the pipette is ±0.05 cm³

The total uncertainty in the 24.50 cm³ of solution from the burette is ±0.15 cm³

Calculate the total percentage error in using the pipette and burette.

A gas syringe that does not have any graduations is calibrated using a known mass of propanone (boiling point = 56.2 °C).

The sealed gas syringe contains 0.146 g of propanone (M_r = 58.0) at a temperature of 95 °C and a pressure of 103 kPa

Calculate the volume, in cm³, of propanone in the gas syringe.

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

The gas syringe is then cooled to 75 °C, without changing the pressure.

Calculate the decrease in volume.

(If you were unable to calculate the volume in Question 07.1, you should use the volume 89 cm³. This is not the correct answer.)

The total uncertainty in using the balance to measure the mass of propanone in Question 07.1 is ±0.001 g

Calculate the uncertainty that this causes in the volume, in cm³, of propanone calculated in Question 07.1.

(If you were unable to calculate the volume in Question 07.1, you should use the volume 89 cm³. This is not the correct answer.)

A 600 cm³ sample of propanone is mixed with 2800 cm³ of oxygen in a container at 60 °C and 100 kPa. The mixture is ignited. When the reaction is complete, the remaining mixture of gases is cooled to 60 °C at 100 kPa

Calculate the total volume of the remaining gas mixture.

Ethyl ethanoate can be made by reacting ethanol with ethanoic acid in the presence of concentrated sulfuric acid.

1. A mixture of ethanol, ethanoic acid, and concentrated sulfuric acid, with anti-bumping granules, is heated under reflux for 10 minutes.

2. The apparatus is rearranged for distillation.

3. The mixture is heated to collect the liquid that distils between 70 and 85 C

4. The distillate is placed in a separating funnel. Aqueous sodium carbonate is added, and a stopper is placed in the funnel. The mixture is shaken, releasing pressure as necessary.

5. The lower aqueous layer is removed and the upper organic layer is placed in a small conical flask.

6. Anhydrous calcium chloride is added to the sample in the conical flask. The flask is shaken well and left for a few minutes.

7. The liquid from the flask is redistilled and the distillate is collected between

State the role of concentrated sulfuric acid in this reaction.

The reaction mixture is flammable.

Suggest how the reaction mixture should be heated in step 1.

Figure 1 shows how a student set up the apparatus for reflux in step 1. You should assume that the apparatus is clamped correctly.

Identify two mistakes the student made in setting up the apparatus. State the problem caused by each mistake.

State why sodium carbonate is added to the distillate in step 4.

Explain why there is a build-up of pressure in the separating funnel.

Give a reason why two layers form in the separating funnel.

Suggest why ethyl ethanoate forms the upper layer.

State why anhydrous calcium chloride is added in step 6.

A student uses the method to prepare some ethyl ethanoate.

The student adds 10.0 cm³ of ethanol (M_r = 46.0) to 5.25 g of ethanoic acid (M_r = 60.0) and obtains 5.47 g of ethyl ethanoate (M_r = 88.0).

For ethanol, density = 0.790 g cm^–3

Determine the limiting reagent.

Calculate the percentage yield of ethyl ethanoate.

Suggest a reason why the percentage yield is not 100%.

Calcium hydroxide is almost insoluble in water, but it reacts with dilute hydrochloric acid.

A student adds 100 cm³ of 0.100 mol dm^–3 hydrochloric acid to 0.600 g of solid calcium hydroxide.

Show, by calculation, that the calcium hydroxide is in excess.

The final mixture contains a saturated solution of Ca(OH)₂ at 293 K

At 293 K

• the solubility of Ca(OH)₂ in this solution is 0.400 g dm^–3

• K_w = 6.80 × 10^–15 mol² dm^–6

Calculate the pH of this solution. Give your answer to two decimal places.

Section B

all questions in this section.

This question is about the preparation of hexan-2-ol. Hexan-2-ol does not mix with water and has a boiling point of 140^oC

Hexan-2-ol can be prepared from hex-1-ene using this method.

a Measure out 11.0 cm³ of hex-1-ene into a boiling tube in an ice bath. b Carefully add 5 cm³ of concentrated phosphoric acid to the hex-1-ene. c After 5 minutes add 10 cm³ of distilled water to the mixture and transfer the boiling tube contents to a separating funnel.

d Shake the mixture and allow it to settle. e Discard the lower (aqueous) layer. f Add a fresh 10 cm³ sample of distilled water and repeat steps d and e. g Transfer the remaining liquid to a beaker. h Add 2 g of anhydrous magnesium sulfate and allow to stand for 5 minutes. i Filter the mixture under reduced pressure. j Distil the filtrate and collect the distillate that boils in the range 130–160^oC

It is important to wear eye protection and a lab coat when completing this experiment.

Suggest, with a reason, one other appropriate safety precaution for this experiment.

Give a reason for adding the distilled water in steps c and f.

Give a reason for adding anhydrous magnesium sulfate in step h.

Complete and label the diagram of the apparatus used to filter the mixture under reduced pressure in step i.

Identify the most likely organic impurity, other than hex-1-ene, in the distillate collected in step j.

Suggest one reason why it could be difficult to remove this impurity.

Calculate the mass, in g, of hexan-2-ol formed from 11.0 cm³ of hex-1-ene if the yield is 31.0%

Give your answer to 1 decimal place.

Density of hex-1-ene = 0.678 g cm⁻³

This question is about olive oil.

A sample of olive oil is mainly the unsaturated fat Y mixed with a small amount of inert impurity.

The structure of Y in the olive oil is shown. Y has the molecular formula C₅₇H₁₀₀O₆ (M_r = 880).

The amount of Y is found by measuring how much bromine water is decolourised by a sample of oil, using this method.

• Transfer a weighed sample of oil to a 250 cm³ volumetric flask and make up to the mark with an inert organic solvent.

• Titrate 25.0 cm³ samples of the olive oil solution with 0.025 mol dm⁻³ Br₂(aq).

A suitable target titre for the titration is 30.0 cm³ of 0.025 mol dm⁻³ Br₂(aq).

Justify why a much smaller target titre would not be appropriate.

Calculate the amount, in moles, of bromine in the target titre.

Calculate a suitable mass of olive oil to transfer to the volumetric flask using your answer to Question 09.1 and the structure of Y. Assume that the olive oil contains 85% of Y by mass.

(If you were unable to calculate the amount of bromine in the target titre, you should assume it is 6.25×10⁻⁴ mol. This is not the correct amount.)

The olive oil solution can be prepared using this method.

• Place a weighing bottle on a balance and record the mass, in g, to 2 decimal places.

• Add olive oil to the weighing bottle until a suitable mass has been added.

• Record the mass of the weighing bottle and olive oil.

• Pour the olive oil into a 250 cm³ volumetric flask.

• Add organic solvent to the volumetric flask until it is made up to the mark.

• Place a stopper in the flask and invert the flask several times.

Suggest an extra step to ensure that the mass of olive oil in the solution is recorded accurately.

Justify your suggestion.

State the reason for inverting the flask several times.

A sample of the olive oil was dissolved in methanol and placed in a mass spectrometer. The sample was ionised using electrospray ionisation. Each molecule gained a hydrogen ion (H⁺) during ionisation. The spectrum showed a peak for an ion with = 345 formed from an impurity in the olive oil. The ion with = 345 was formed from a compound with the empirical formula C₅H₁₀O

Deduce the molecular formula of this compound.

Show your working.

Molecular formula 12

Complete combustion of 0.0100 mol of an organic acid produced 0.0200 mol of carbon dioxide.

The same amount of the acid required 20 cm³ of 1.00 mol dm^–3 NaOH (aq) for neutralisation.

Which could be the formula of the acid?

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.

Coconut oil contains a triester with three identical R groups. This triester reacts with potassium hydroxide.

Complete the equation by drawing the structure of the other product of this reaction in the box.

Name the type of compound shown by the formula RCOOK

Give one use for this type of compound.

The triester in coconut oil has a relative molecular mass, M_r = 638.0 In the equation shown at the start of Question 01, R represents an alkyl group that

A 1.450 g sample of coconut oil is heated with 0.421 g of KOH in aqueous ethanol until all of the triester is hydrolysed. The mixture is cooled. The remaining KOH is neutralised by exactly 15.65 cm³ of 0.100 mol dm^–3 HCl

Calculate the percentage by mass of the triester (M_r= 638.0) in the coconut oil.

Suggest why aqueous ethanol is a suitable solvent when heating the coconut oil with KOH.

Give a safety precaution used when heating the mixture. Justify your choice.

Safety precaution

A student plans an experiment to investigate the yield of propanoic acid when a sample of propan-1-ol is oxidised.

Figure 4 shows the apparatus that the student plans to use for the experiment.

The student’s teacher says that the apparatus is not safe.

Give two reasons why the apparatus shown in Figure 4 is not safe.

Give one additional reagent that is needed to form any propanoic acid.

State two more mistakes in the way the apparatus is set up in Figure 4.

State the purpose of the small glass beads in the flask in Figure 4.

After correcting the mistakes, the student heats a reaction mixture containing 6.50 g of propan-1-ol with an excess of the oxidising agent. The propanoic acid separated from the reaction mixture has a mass of 3.25 g

State the name of the technique used to separate the propanoic acid from the reaction mixture.

Calculate the percentage yield of propanoic acid.

Which compound needs the greatest amount of oxygen for the complete combustion of 1 mol of the compound?

Nitration of 1.70 g of methyl benzoate (M_r = 136.0) produces methyl 3-nitrobenzoate

What mass, in g, of methyl 3-nitrobenzoate is produced?

Describe the instruction that is missing from step 4 of the method.

Justify why this step is necessary.

Suggest a suitable piece of apparatus to measure out the ethanoic anhydride in step 5.

Identify a hazard of using concentrated phosphoric acid in step 6.

Complete the equation for the reaction of salicylic acid with ethanoic anhydride to produce aspirin.

A 6.01 g sample of salicylic acid (M_r = 138.0) is reacted with

The density of ethanoic anhydride is 1.08 g cm^–3

Show by calculation which reagent is in excess.

Calculate the mass, in g, of aspirin (M_r = 180.0) produced.

Suggest two ways in which the melting point of the crude aspirin collected in step 9 would differ from the melting point of pure aspirin.

The crude aspirin can be purified by recrystallisation using hot ethanol (boiling point = 78 °C) as the solvent.

Describe two important precautions when heating the mixture of ethanol and crude aspirin.

The pure aspirin is filtered under reduced pressure. A small amount of cold ethanol is then poured through the Buchner funnel.

Explain the purpose of adding a small amount of cold ethanol.

A sample of the crude aspirin is kept to compare with the purified aspirin.

Describe one difference in appearance you would expect to see between these two solid samples.

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.

When heated, a sample of potassium chlorate(V) (KClO₃) produced 67.2 cm³ of oxygen, measured at 298 K and 110 kPa

What is the amount, in moles, of potassium chlorate(V) that has decomposed?

The gas constant, R = 8.31 J K^–1 mol^–1

A student rinsed the apparatus before starting an acid-base titration. The results of the titration showed that the volume of acid added from the burette was larger than expected.

Which is a possible reason for this?

This question is about periodicity, the Period 4 elements and their compounds.

State the meaning of the term periodicity.

Identify the element in Period 4 with the highest electronegativity value.

Identify the element in Period 4 with the largest atomic radius. Explain your answer.

The equations for two reactions of arsenic(III) oxide are shown.

Name the property of arsenic(III) oxide that describes its ability to react in these two

Complete the equation for the formation of arsenic hydride.

Sulfur trioxide decomposes on heating to form an equilibrium mixture containing sulfur dioxide and oxygen.

A sample of sulfur trioxide was heated and allowed to reach equilibrium at a given temperature. The equilibrium mixture contained 6.08 g of sulfur dioxide.

Calculate the mass, in g, of oxygen gas in the equilibrium mixture.

A different mass of sulfur trioxide was heated and allowed to reach equilibrium at 1050 K

The amounts of each substance in the equilibrium mixture are shown in Table 4.

For this reaction at 1050 K the equilibrium constant, K_p = 7.62 x 10⁵ Pa

Calculate the mole fraction of each substance at equilibrium. Give the expression for the equilibrium constant, K_p Calculate the total pressure, in Pa, of this equilibrium mixture.

K_p

For this reaction at 1050 K the equilibrium constant, K_p = 7.62 x 10⁵ Pa For this reaction at 500 K the equilibrium constant, K_p = 3.94 x 10⁴ Pa

Explain how this information can be used to deduce that the forward reaction is endothermic.

Use data from Question 07.3 to calculate the value of K_p, at 500 K, for the equilibrium represented by this equation.

A student prepared cyclohexene by heating cyclohexanol with concentrated phosphoric acid. The cyclohexene produced was distilled off from the reaction mixture.

Complete the diagram of the apparatus used to distil the cyclohexene from the reaction mixture at 83 °C.

The distillate was shaken with saturated sodium chloride solution. The cyclohexene was separated from the aqueous solution using a separating funnel.

State why cyclohexene can be separated from the aqueous solution using the separating funnel.

The cyclohexene separated in Question 02.2 was obtained as a cloudy liquid. The student dried this cyclohexene by adding a few lumps of anhydrous calcium chloride and allowing the mixture to stand.

Give one observation that the student made to confirm that the cyclohexene was dry.

In this preparation, the student added an excess of concentrated phosphoric acid to

Calculate the percentage yield of cyclohexene obtained. Give your answer to the appropriate number of significant figures.

Cyclohexene reacts with bromine.

Complete the mechanism for this reaction.

Paracetamol is a medicine commonly used to relieve mild pain. Traditionally, paracetamol has been made industrially in a three-step synthesis from

Name the mechanism of the reaction in Step 1.

Complete the equation for the reaction in Step 2.

In theory, either ethanoyl chloride or ethanoic anhydride could be used in Step 3.

Complete the mechanism for the reaction of 4-aminophenol with ethanoyl chloride. RNH₂ is used to represent 4-aminophenol in this mechanism.

In practice, ethanoic anhydride is used in the industrial synthesis rather than ethanoyl chloride.

Give one reason why ethanoyl chloride is not used in the industrial synthesis.

In Step 3 other aromatic products are formed as well as paracetamol.

Draw the structure of one of these other aromatic products.

Chemists have recently developed a two-step process to produce paracetamol from phenol. In the first step, phenol is oxidised to hydroquinone.

In the second step, hydroquinone reacts with ammonium ethanoate to form paracetamol.

Complete the equation for this second step.

Calculate the mass, in kg, of hydroquinone (M_r = 110.0) needed to produce 250 kg of paracetamol.

Sodium thiosulfate reacts with dilute hydrochloric acid as shown.

Give the simplest ionic equation for this reaction.

The gas SO₂ is a pollutant.

State the property of SO₂ that causes pollution when it enters rivers.

Give an equation to show the reaction of SO₂ with water.

Draw a diagram to show the shape of a molecule of H₂O Include any lone pairs of electrons.

State the HOH bond angle.

Explain this shape and bond angle.

Diagram

The initial rate of the reaction between sodium thiosulfate and hydrochloric acid can be monitored by measuring the time taken for a fixed amount of sulfur to be produced.

Describe an experiment to investigate the effect of temperature on the initial rate of this reaction.

Include

• a brief outline of your method

• how you will measure the time taken for a fixed amount of sulfur to be formed

• how you will present your results in graphical form

• a sketch of the graph that you would expect.

This question is about sulfuric acid and its salts.

Draw the displayed formula of a molecule of H₂SO₄

In aqueous solution, sulfuric acid acts as a strong acid. The H₂SO₄ dissociates to form HSO₄ ions and H⁺ ions.

The HSO₄ ions act as a weak acid and dissociate to form SO₄² ions and H⁺ ions.

Give an equation to show each stage in the dissociation of sulfuric acid in aqueous solution.

Include appropriate arrows in your equations.

A student is required to make 250 cm³ of an aqueous solution that contains an accurately measured mass of sodium hydrogensulfate (NaHSO₄).

Describe the method that the student should use to make this solution.

A solution that contains 605 mg of NaHSO₄ in 100 cm³ of solution has a pH of 1.72

Calculate the value of K_a for the hydrogensulfate ion (HSO₄) that is behaving as a weak acid. Give your answer to three significant figures.

Some sodium sulfate is dissolved in a sample of the solution from question 02.4.

Explain why this increases the pH of the solution.

The percentage by mass of iron in a steel wire is determined by a student.

The student

• reacts 680 mg of the wire with an excess of sulfuric acid, so that all of the iron in the

Give the equation for the reaction between iron and sulfuric acid.

The titration results are shown in Table 3.

Calculate the mean titre.

Give the overall ionic equation for the oxidation of Fe² by manganate(VII) ions, in acidic conditions.

State the colour change seen at the end point of the titration.

Name the piece of apparatus used for these stages of the method.

Adding the potassium manganate(VII) solution

The balance used to weigh the 680 mg of iron wire has an uncertainty of ±0.005 g

A container was weighed and its mass was subtracted from the total mass of the container and wire.

Calculate the percentage uncertainty in using the balance.

Which amount of sodium hydroxide would react exactly with 7.5 g of a diprotic acid,

Lead(II) nitrate and potassium iodide react according to the equation

In an experiment, 25.0 cm³ of a 0.100 mol dm^–3 solution of each compound are mixed together.

Which amount, in mol, of lead(II) iodide is formed?

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 s-block metals.

Give the full electron configuration for the calcium ion, Ca²⁺

Explain why the second ionisation energy of calcium is lower than the second ionisation energy of potassium.

Identify the s-block metal that has the highest first ionisation energy.

Give the formula of the hydroxide of the element in Group 2, from Mg to Ba, that is least soluble in water.

A student added 6 cm³ of 0.25 mol dm^–3 barium chloride solution to 8 cm³ of 0.15 mol dm^–3 sodium sulfate solution. The student filtered off the precipitate and collected the filtrate.

Give an ionic equation for the formation of the precipitate. Show by calculation which reagent is in excess. Calculate the total volume of the other reagent which should be used by the student so that the filtrate contains only one solute.

Total volume of other reagent

A sample of strontium has a relative atomic mass of 87.7 and consists of three

State why the isotopes of strontium have identical chemical properties. Calculate the percentage abundance of the⁸⁸Sr isotope in this sample.

Why isotopes of strontium have identical chemical properties

A time of flight (TOF) mass spectrum was obtained for a sample of barium that

Identify the ion with the longest time of flight.

A¹³⁷Ba⁺ ion travels through the flight tube of a TOF mass spectrometer with a

The Avogadro constant, L = 6.022 × 10²³ mol^–1

Calculate the length of the flight tube in metres. Give your answer to the appropriate number of significant figures.

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.

A student added 627 mg of hydrated sodium carbonate (Na₂CO₃.xH₂O) to 200 cm³ of 0.250 mol dm^–3 hydrochloric acid in a beaker and stirred the mixture. After the reaction was complete, the resulting solution was transferred to a volumetric flask, made up to 250 cm³ with deionised water and mixed thoroughly. Several 25.0 cm³ portions of the resulting solution were titrated with 0.150 mol dm^–3 aqueous sodium hydroxide. The mean titre was 26.60 cm³ of aqueous sodium hydroxide.

Show your working. Give your answer as an integer.

Cyclohexene (boiling point = 83 °C) can be prepared by the dehydration of cyclohexanol (boiling point = 161 °C) using concentrated phosphoric acid.

A student prepared cyclohexene by placing 10 cm³ of cyclohexanol (density = 0.96 g cm^–3) into a round-bottomed flask. 3 cm³ of concentrated phosphoric acid were then carefully added to the flask. The student added a few anti-bumping granules and set up the apparatus shown in Figure 3.

• The student heated the mixture and collected the liquid that distilled at temperatures below 100 °C

• The distillate was poured into a separating funnel and washed by shaking with sodium carbonate solution.

• Periodically, the separating funnel was inverted and the tap opened.

• The aqueous layer was discarded and the final organic product was dried using anhydrous calcium chloride.

• After the product was dried, the drying agent was removed by filtration under reduced pressure.

The student collected 5.97 g of cyclohexene in the experiment.

Calculate the percentage yield of cyclohexene.

Describe a test-tube reaction, on the product, to show that the cyclohexanol had been dehydrated. State what you would observe.

Suggest why sodium carbonate solution was used to wash the distillate.

Explain why it is important to open the tap of the separating funnel periodically.

Give a property of anhydrous calcium chloride, other than its ability to absorb water, that makes it suitable as a drying agent in this preparation.

Describe the apparatus used to remove the drying agent by filtration under reduced pressure. Your description of the apparatus can be either a labelled diagram or a description in words.

A sample of cyclohexene has been contaminated with cyclohexanol. The cyclohexene can be separated from the cyclohexanol by column chromatography. Silica gel is used as the stationary phase and hexane as the mobile phase.

Explain why cyclohexene has a shorter retention time than cyclohexanol.

Explain how an infrared spectrum would confirm that the cyclohexene obtained from the chromatography column did not contain any cyclohexanol.

A student carried out an experiment to find the temperature rise for a reaction between hydrochloric acid and sodium hydroxide solution.

• The student used a measuring cylinder to place 50 cm³ of 0.400 mol dm^–3 hydrochloric acid into a glass beaker.

• The student recorded the temperature at one-minute intervals for three minutes.

• At the fourth minute the student added 50 cm³ of 0.400 mol dm^–3 sodium hydroxide solution and stirred to mix the solutions, but did not record the temperature.

The student recorded the temperature at one-minute intervals for a further eight minutes.

The results are shown in Table 3.

Plot a graph of temperature against time on the grid opposite. Use your graph to find the temperature rise, ∆ T, at the fourth minute. Show your working on the graph by drawing suitable lines of best fit.

The uncertainty in each of the temperature readings from the thermometer used in this experiment was ±0.1° C

Calculate the percentage uncertainty in the value for the temperature rise.

Suggest a change to the experiment that would minimise heat loss.

Suggest and explain another change to the experiment that would decrease the percentage uncertainty in the use of the same thermometer.

A second student completed an experiment to determine the enthalpy of neutralisation for the reaction between ethanedioic acid solution (HOOCCOOH) and potassium hydroxide solution.

The student added 25 cm³ of 0.80 mol dm^–3 ethanedioic acid solution to 75 cm³ of 0.60 mol dm^–3 potassium hydroxide solution. The temperature increased by 3.2 ° C

Give an equation for the reaction between ethanedioic acid solution and potassium hydroxide solution. Calculate the enthalpy change (∆ H) per mole of water formed in this reaction. Assume that the specific heat capacity of the reaction mixture is 4.2 J K^–1g^–1 Assume that the density of the reaction mixture is 1.00 g cm^–3

In a similar experiment to that in Question 04.5, the enthalpy of neutralisation for the reaction between sulfuric acid and potassium hydroxide solution was found to be –57.0 kJ mol^–1 per mole of water formed.

Suggest an explanation for the difference between this value and your answer to Question 04.5. (If you were unable to obtain an answer to Question 04.5 you should assume a value of –28.5 kJ mol^–1. This is not the correct answer.)

Turn over for Section B

Figure 1 shows some compounds made from a halogenoalkane.

Draw the displayed formula of compound J.

Name the mechanism for Reaction 2 and give an essential condition used to ensure that CH₃CH₂CH₂NH₂ is the major product.

Name of mechanism

Calculate the mass, in grams, of CH₃CH₂CH₂NH₂ produced from 25.2 g of CH₃CH₂CH₂Br in Reaction 2 assuming a 75.0% yield.

Give your answer to the appropriate number of significant figures.

When Reaction 2 is carried out under different conditions, a compound with molecular formula C₉H₂₁N is produced. Draw the skeletal formula of the compound. Identify the functional group in the compound including its classification.

Skeletal formula

Identify the reagent and conditions used in Reaction 3.

Name and outline a mechanism for Reaction 3.

Name of mechanism

Mechanism

Give the full IUPAC name of isomer P.

A sample of P was mixed with an excess of oxygen and the mixture ignited. After cooling to the original temperature, the total volume of gas remaining was

When this gas mixture was passed through aqueous sodium hydroxide, the carbon dioxide reacted and the volume of gas decreased to 155 cm³

Both gas volumes were measured at 25 °C and 105 kPa

Write an equation for the combustion of P in an excess of oxygen and calculate the mass, in mg, of P used.

The gas constant R = 8.31 J K⁻¹ mol⁻¹

Mass of P used mg

Isomer Q (C₆H₁₀O₂) is a cyclic compound. The infrared spectrum of Q is shown in Figure 4 and the¹³C NMR spectrum of Q is shown in Figure 5.

Use these spectra and Tables A and C in the Data Booklet to deduce the structure of Q. In your answer, state one piece of evidence you have used from each spectrum.

Structure of Q.

Evidence from Figure 4

Evidence from Figure 5

Isomers R and S are shown.

Although the¹³C spectra of R and S both show the same number of peaks, the spectra can be used to distinguish between the isomers.

Justify this statement using Table C from the Data Booklet.

Give the number of peaks for each isomer.

Justification

Although the¹H spectra of R and S both show the same number of peaks, the spectra can be used to distinguish between the isomers.

Justify this statement using the splitting patterns of the peaks.

Give the number of peaks for each isomer.

Justification

The action of heat on 5-hydroxyhexanoic acid can lead to two different products.

On gentle heating, 5-hydroxyhexanoic acid loses water to form a cyclic

Under different conditions, 5-hydroxyhexanoic acid forms a polyester.

Draw the structure of T.

Draw the repeating unit of the polyester and name the type of polymerisation.

Structure of T

Repeating unit of polyester

Type of polymerisation

Isomer U is shown.

The polymer formed by U and the polymer formed by 5-hydroxyhexanoic acid in Question 10.6 both contain ester groups that can be hydrolysed.

Draw the repeating unit of the polymer formed by U.

Justify the statement that, although both polymer structures contain ester groups, the polymer formed by U is not biodegradable.

Repeating unit of polymer formed by U.

Justification