AQA A Level Chemistry Paper 2 June 2022 question paper 7405/2

An acidified solution of butanone reacts with iodine as shown.

Draw the displayed formula for CH₃CH₂COCH₂I

Give the name of CH₃CH₂COCH₂I

Displayed formula

The rate equation for the reaction is

Table 1 shows the initial concentrations used in an experiment.

The initial rate of reaction in this experiment is 1.45×10⁻⁴ mol dm⁻³ s⁻¹

Calculate the value of the rate constant, k, for the reaction and give its units.

Calculate the initial rate of reaction when all of the initial concentrations are halved.

An experiment was done to measure the time, t, taken for a solution of iodine to react completely when added to an excess of an acidified solution of butanone.

Suggest an observation used to judge when all the iodine had reacted.

The experiment was repeated at different temperatures. Figure 1 shows how varied with temperature for these experiments.

Describe and explain the shape of the graph in Figure 1.

Deduce the time taken for the reaction at 35^oC

For a different reaction, Table 2 shows the value of the rate constant at different temperatures.

This equation can be used to calculate the activation energy, E_a

Calculate the value, in kJ mol⁻¹, of the activation energy, E_a

The gas constant, R = 8.31 J K⁻¹mol⁻¹

Name and outline the mechanism for the reaction of butanone with KCN followed by dilute acid.

Name of mechanism

Outline of mechanism

Tetrafluoroethene is made from chlorodifluoromethane in this reversible reaction.

A 2.00 mol sample of CHClF₂ is placed in a container of volume 23.2 dm³ and heated. When equilibrium is reached, the mixture contains 0.270 mol of CHClF₂

Calculate the amount, in moles, of C₂F₄ and of HCl in the equilibrium mixture.

Give an expression for K_c for this equilibrium.

Calculate a value for K_c

Give its units.

State and explain the effect of using a higher temperature on the equilibrium yield of tetrafluoroethene.

Chemists provided evidence that was used to support a ban on the use of chlorodifluoromethane as a refrigerant.

Many refrigerators now use pentane as a refrigerant.

State the environmental problem that chlorodifluoromethane can cause.

Give one reason why pentane does not cause this problem.

Environmental problem

This question is about 2-methylbut-1-ene.

Name the mechanism for the reaction of 2-methylbut-1-ene with concentrated sulfuric acid.

Outline the mechanism for this reaction to form the major product.

Outline of mechanism to form major product

Draw the structure of the minor product formed in the reaction in Question 03.1

Explain why this is the minor product.

Structure of minor product

Draw the skeletal formula of a functional group isomer of 2-methylbut-1-ene.

2-methylbut-1-ene can form a polymer.

State the type of polymerisation.

Draw the repeating unit for the polymer formed.

Type of polymerisation

Repeating unit

Proteins are polymers made from amino acids. Part of the structure of a protein is shown.

–Cys–Ser–Asp–Phe–

Each amino acid in the protein is shown using the first three letters of its name.

Identify the type of protein structure shown.

Tick (✓) one box.

Draw a structure for the –Cys–Ser– section of the protein. Use the Data Booklet to help you answer this question.

Name the other substance formed when two amino acids react together to form part of a protein chain.

The general structure of an amino acid is shown.

R represents a group that varies between different amino acids. R groups can interact and contribute to protein structure.

Explain why the strength of the interaction between two cysteine R groups differs from the strength of the interaction between a serine R group and an aspartic acid R group.

Use the Data Booklet to help you answer this question.

Deduce the type of interaction that occurs between a lysine R group and an aspartic acid R group.

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 compound X with the empirical formula C₂H₄O

Figure 2 shows the infrared spectrum of X.

Figure 3 shows the¹³C NMR spectrum of X.

The¹H NMR spectrum of X shows four peaks with different chemical shift values. Table 3 gives data for these peaks.

Show how information from Figure 2, Figure 3 and Table 3 can be used to deduce the structure of compound X.

The answer space for this question continues on the next page

This question is about esters.

Figure 4 shows an incomplete mechanism for the reaction of an ester with aqueous sodium hydroxide.

Add three curly arrows to complete the mechanism in Figure 4.

Name the type of reaction shown in Figure 4.

Deduce the role of the CH₃O⁻ ion in step 3 shown in Figure 4.

A triester in vegetable oil reacts with sodium hydroxide in a similar way.

Give a use for a product of this reaction.

Benzene reacts with methanoyl chloride (HCOC l) in the presence of a catalyst.

Give an equation for the overall reaction when benzene reacts with methanoyl chloride.

Name the organic product.

Identify the catalyst needed in this reaction.

Give an equation to show how the catalyst is used to form the electrophile, [HCO]⁺

Outline the mechanism for the reaction of benzene with the electrophile, [HCO]⁺

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

This question is about the reaction scheme shown.

State the reagents needed for step 1 and the reagents needed for step 2.

Give the name of the mechanism for the reaction in step 3.

Name the reagent for step 4.

State a necessary condition for step 4.

Amine A is formed in step 2 and amine B is formed in step 5.

Explain why the yield of B in step 5 is less than the yield of A in step 2.

Explain why amine B is a stronger base than amine A.