AQA GCE AS Level Chemistry Paper 2 June 2023 question paper 7404/2

This question is about the analysis of organic compounds.

For each pair of compounds in Questions 01.1 and 01.2, give a reagent (or combination of reagents) that could be added separately to each compound in a single reaction to distinguish between them.

State what is observed in each case.

CH₃CH₂CH₂CHO and CH₃CH₂CH(OH)CH₃

Observation with CH₃CH₂CH₂CHO

Observation with CH₃CH₂CH(OH)CH₃

Cyclohexane and cyclohexene

Observation with cyclohexane

Observation with cyclohexene

Table 1 gives the precise relative molecular masses (M_r) of some organic compounds measured using high resolution mass spectrometry.

Use these data to find the relative atomic masses (A_r) of hydrogen and carbon. Give your answers to 4 decimal places.

Use these calculated A_r values to find the relative molecular mass (M_r) of C₆H₆ Give your answer to 4 decimal places.

This question is about fuels.

Crude oil is separated into fractions by fractional distillation.

State the meaning of the term ‘fraction’ in this context.

Petrol for cars contains branched and cyclic alkanes produced by catalytic cracking.

Identify the catalyst used in this process.

3-Ethyl-4-methylhexane is a branched alkane in petrol.

Draw the skeletal formula of this alkane.

Give the equation for the complete combustion of 3-ethyl-4-methylhexane. Use the molecular formula for 3-ethyl-4-methylhexane in your equation.

Carbon dioxide is a product from the combustion of petrol in cars. Carbon dioxide acts as a greenhouse gas when it absorbs infrared radiation.

Give one reason why carbon dioxide absorbs infrared radiation.

Nitrogen monoxide (NO) is formed when petrol is burned in cars.

State one environmental problem that NO causes.

State what is used to remove NO from the exhaust gases formed in petrol-fuelled cars.

Environmental problem

Petrol sold in the UK contains 10% bioethanol. Bioethanol is ethanol made from crops by fermentation and is considered to be carbon-neutral.

State what is meant by the term ‘carbon-neutral’.

This question is about reactions of halogenoalkanes with hydroxide ions.

Outline the mechanism for the nucleophilic substitution reaction of 1-bromobutane with sodium hydroxide.

A student investigated the rate of nucleophilic substitution of halogenoalkanes with hydroxide ions.

Identical concentrations of 1-bromobutane and 1-iodobutane were reacted separately with sodium hydroxide solution under the same conditions.

The concentration of halide ions was monitored during each experiment.

Figure 1 shows the student’s results.

State how Figure 1 shows that the rate of reaction of 1-iodobutane is faster than the rate of reaction of 1-bromobutane.

State why the rates are different.

1-Methylcyclohexene and limonene are cyclic alkenes with a citrus smell. 1-Methylcyclohexene is manufactured and used in the chemical industry. Limonene is found naturally in orange peel.

1-Methylcyclohexene reacts with HBr to form two structural isomers. The major product is 1-bromo-1-methylcyclohexane.

Name and outline the mechanism for the formation of this major product.

Outline of mechanism

Draw the skeletal formula of the minor product formed in the reaction in Question 04.1

Explain why the products are formed in different amounts.

Skeletal formula

Draw the structure of the major product when an excess of HBr reacts with limonene.

A student is provided with a 0.0300 mol sample of an alcohol. The student decides to identify the alcohol using an experiment to determine its enthalpy of combustion.

Figure 2 shows the apparatus used.

The student finds that when all the alcohol is burned, the temperature of the water increases from 18.9 °C to 78.1 °C

Calculate the enthalpy of combustion, in kJ mol^–1, for the alcohol. The specific heat capacity of water, c = 4.18 J g^–1 K^–1

Enthalpy of combustion
kJ mol

Table 2 shows the enthalpies of combustion of some alcohols.

Explain how your answer to Question 05.1 suggests that the alcohol is butan-1-ol.

(If you have been unable to obtain an answer for Question 05.1, assume that the

The equation for the complete combustion of gaseous pentan-1-ol is shown.

Table 3 shows some bond enthalpy data.

Use data from Table 3 to calculate a value for the mean C–C bond enthalpy in pentan-1-ol.

C–C bond enthalpy
kJ mol

The energy stored in fuels can be compared using energy density values

Calculate the energy density of butan-1-ol.

enthalpy of combustion of butan-1-ol = –2676 kJ mol^–1

Energy density
kJ dm

This question is about intermolecular forces in some organic compounds.

Table 4 gives some information about three organic compounds.

Suggest why tetrachloromethane molecules are non-polar.

Explain why tetrachloromethane has a higher boiling point than dichloromethane.

Propan-1-ol has a higher boiling point than the other two compounds because of hydrogen bonding.

Describe the hydrogen bonding in propan-1-ol.

This question is about the preparation of 2,3,3-trimethylbut-1-ene.

The preparation is done by heating the alcohol with concentrated phosphoric acid, that acts as a catalyst.

Figure 3 shows the apparatus used.

The distillate is collected in the range 77–82 °C

Explain why the water should enter the condenser at the bottom and not at the top.

Name and complete the mechanism for this reaction.

Name of mechanism

In a similar experiment, 12.0 cm³ of 2,3,3-trimethylbutan-1-ol (M_r = 116.0) produces 6.12 g of 2,3,3-trimethylbut-1-ene.

Calculate the percentage yield.

Draw the Maxwell–Boltzmann distribution curves for a fixed mass of a gas at two different temperatures. This gas decomposes when heated.

By reference to these distribution curves, explain why the rate of decomposition of this gas increases at higher temperatures.

Only one answer per question is allowed.

Do not use additional sheets for this working.

Which monomer forms this polymer?

Which equation represents a propagation step in the chlorination of methane?

Which is the overall equation for the reaction of CCl₃CH₂CCl₃ with an excess of chlorine in ultraviolet radiation?

Most scientists believe that ozone in the upper atmosphere should not be allowed to become depleted.

Which is a valid reason for this belief?

Which is not a possible product of the reaction of this compound with

The infrared spectrum of an organic compound is shown.

Which compound could produce this spectrum?

Which reaction results in an overall change in shape around a carbon atom?

Which statement about the industrial production of ethanol from ethene at 300 °C is correct?

What is the minimum volume, in dm³, of air needed for the complete combustion of

Assume that air contains 20% of oxygen by volume.

Assume that all volumes are measured at the same temperature and pressure.

Which is the IUPAC name for this compound?

Magnesium reacts with an acid to form hydrogen gas.

Line X on the graph shows how the volume of hydrogen gas varies with time when 50 cm³ of 0.50 mol dm^–3 acid reacts with an excess of magnesium.

The reaction is repeated under the same conditions but using 25 cm³ of 1.50 mol dm^–3 acid. The magnesium is in excess.

Which line represents this second reaction?

Which compound has the greatest M_r?

Which compound has the empirical formula C₂H₄O?

The alcohol CH₃CH₂CH₂OH can be oxidised.

Which compound cannot be produced by oxidation of this alcohol?

What is the atom economy for the formation of ethylamine in this reaction?