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AQA MERGED QUESTION PAPER AND MARK SCHEME PAPER 2-7405/2 ORGANIC AND PHYSICAL CHEMISTRY FOR JUNE 2024
Typology: Exams
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For Examiner’s Use
Question Mark 1 2 3 4 5 6 7 8 9
10 11
TOTAL
Answer all questions in the spaces provided.
(^0 1) Propanone reacts with bromine in alkaline conditions.
CH 3 COCH 3 + Br 2 + OH–^ ⟶ CH 3 COCH 2 Br + Br –^ + H 2 O
The rate equation for this reaction is
Rate = k [CH 3 COCH 3 ] [OH–]
(^0 1). 1 Sketch a graph on the axes provided to show how, at constant temperature, the concentration of bromine changes during this reaction. [1 mark]
0 1. (^3) Figure 1 shows an incomplete mechanism for this reaction.
Figure 1
Complete the mechanism in Figure 1 by adding four curly arrows and any relevant lone pair(s) of electrons. [ 4 marks]
0 1. (^4) Use evidence from the rate equation to explain why Step 1 is the rate determining step. [1 mark]
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Do not write outside the 0 2. (^2) Give the expression for the equilibrium constant, K c^ box
Calculate the value of K c and deduce its units. [ 4 marks]
K c
Value of K c Units
(^0 2). 3 Explain why the amount of S increases when water is added to the equilibrium mixture. [ 2 marks]
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Do not write outside the (^0 3) This question is about hydrocarbons.^ box
(^0 3). 1 Eicosane (C 20 H 42 ) can be cracked by heating to 700 K in the presence of a catalyst.
The products are
C 20 H 42 ⟶ C 8 H 10 + C 6 H 14 +
Complete the equation for this reaction.
Give a suitable catalyst for this reaction. [2 marks]
Catalyst
0 3. (^2) Figure 2 shows the 13 C NMR spectrum for the aromatic hydrocarbon C 8 H 10
Figure 2
Do not write outside the 0 3. (^4) A sample of butane has a volume of 20 cm 3 at room temperature and pressure.^ box
The sample is burned completely in 1350 cm 3 of air.
The final mixture is cooled to room temperature and pressure.
1 2 O^2 ⟶^4 CO^2 + 5^ H^2 O
Calculate the total volume of gas in the final mixture. Assume that air contains 21% by volume of oxygen. [ 4 marks]
Total volume of gas remaining cm 3
(^0 3). 5 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. [2 marks]
Environmental problem
Formula of compound^10
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Do not write outside the 0 4. (^3) In Step 2 the reaction mixture from Step 1 is shaken with aqueous sodium carbonate.^ box
State the purpose of the sodium carbonate.
Suggest a precaution that should be taken while this mixture is shaken in the separating funnel.
Give a reason for your suggested precaution. [ 3 marks]
Purpose of sodium carbonate
Precaution
Reason
(^0 4). 4 Give the reason for the use of anhydrous magnesium sulfate in Step 3. [ 1 mark]
0 4. (^5) Suggest how the purity of the ester can be confirmed during the distillation in Step 4. [ 1 mark]
Do not write outside the (^0 6) Compounds V , W , X and Y are isomers with the molecular formula C 5 H 10 O 2^ box
Isomers V and W are carboxylic acids with formulas that can be written as C 4 H 9 COOH
0 6. (^1) Give an equation for the reaction of C 4 H 9 COOH with sodium hydrogencarbonate. [ 1 mark]
0 6. (^2) Isomer V has an asymmetric carbon atom.
Deduce the structure of V. [ 1 mark]
(^0 6). 3 Isomer W has four peaks in its 1 H NMR spectrum.
Deduce the structure of W.
Deduce the integration ratio for the four peaks in the 1 H NMR spectrum of W. [ 2 marks]
Structure
Integration ratio
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Do not write outside the 0 6. (^4) Isomer X has three singlets with integration ratio 1:3:6 in its 1 H NMR spectrum.^ box
Deduce the structure of X.
Explain why the peaks in the 1 H NMR spectrum are singlets. [ 2 marks]
Structure
Explanation
Question 6 continues on the next page
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Do not write outside the (^0 7) Compound L ( M r = 88.0) contains carbon, hydrogen and oxygen only.^ box
A 6.56 × 10–4^ mol sample of L burns completely in air to form 2.62 × 10–3^ mol of water and 2.62 × 10–3^ mol of carbon dioxide.
Deduce the formula of L. Show your working. [4 marks]
Formula of L 4
Do not write outside the (^0 8) This question is about an organic synthesis.^ box
0 8. (^1) Name the mechanism in Step 1.
State the reagent(s) used for Step 1. [ 2 marks]
Name of mechanism
Reagent(s)
(^0 8). 2 Identify compound J.
State the reagent(s) and conditions needed for Step 2. [ 2 marks]
Compound J
Reagent(s) and conditions
