Chemistry · Edexcel 9CH0 · Paper 2: Advanced Organic and Physical Chemistry · June 2018
This question is about alkanes.
The reaction of ethane and chlorine in UV radiation produces chloroethane.
This reaction is classified as
(1)
The black smoke produced from the incomplete combustion of alkane fuels is
(1)
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This question is about how catalysts work.
Gaseous reactants attach to the catalytic surface by the process of
(1)
Catalytic converters of car exhaust systems have internal honeycomb structures as shown.
Explain why the honeycomb structure is used in a car exhaust system.
(2)
Chromatography is a technique used to separate the components of a mixture.
A sample of a tripeptide was hydrolysed and then placed on a thin layer chromatography (TLC) plate. Samples of possible amino acids present were also placed on the TLC plate for reference. A simplified diagram of the developed TLC plate is shown.
Calculate the Rf value for the amino acid lysine. Give your answer to an appropriate number of significant figures.
(1)
Identify by name the two amino acids present in the tripeptide, giving a reason for the lack of a third spot.
(3)
Give two reasons why different amino acids have different Rf values.
(2)
In chromatography, a ‘locating’ reagent is often used when the components in a mixture are colourless.
Which reagent is used to locate the amino acid spots?
(1)
Gas chromatography can be used both to separate the components in a mixture and to determine the amount of each present.
State why argon and nitrogen are suitable carrier gases for gas chromatography.
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A mixture containing one part substance X, two parts substance Y and one part substance Z was separated by gas chromatography.
Substance X has a retention time of 10 seconds, substance Y of 15 seconds and substance Z of 40 seconds.
Complete the sketch of this chromatogram.
(3)
Many vehicles are fitted with airbags which provide a gas-filled safety cushion to protect the occupant of the vehicle if there is a crash.
The first reaction in airbags is the thermal decomposition of sodium azide, NaN3, to form sodium and nitrogen gas.
Write the equation for this decomposition of sodium azide. State symbols are not required.
(1)
In the reaction in (a)(i), a typical airbag is inflated by about 67 dm3 of gas. Calculate the minimum mass of sodium azide, in grams, needed to produce this volume of gas. Use the Ideal Gas Equation and give your answer to an appropriate number of significant figures.
For the purpose of this calculation, assume that the temperature is 300 °C and the pressure is 140 000 Pa.
(4)
The second reaction in the airbag is between the sodium produced in the reaction (a)(i) and potassium nitrate.
Balance the above equation, justifying your answer in terms of the changes in oxidation numbers.
(3)
The third reaction in the airbag is between the metal oxides and silicon dioxide.
State the type of reaction taking place and justify why this reaction is necessary.
(3)
The Maxwell-Boltzmann distribution diagram shows the molecular energies for the gaseous system immediately after the airbag has been deployed.
What is the change in shape of the curve when the airbag cools ?
(1)
Some alcohols can be oxidised by acidified sodium dichromate(VI), Na2Cr2O7.
Balance the ionic half-equation for the reduction of the dichromate(VI) ion. Give the colours of all of the species involved, or state colourless if appropriate.
(2)
Reflux apparatus can be used to carry out the oxidation of alcohols.
This Liebig condenser has been set up incorrectly. Add shading to the diagram to show the water in the condenser, illustrating the effect of the incorrect water flow.
(1)
State how the granules prevent bumping.
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Using the apparatus for distillation instead of reflux is not an efficient way to produce ethanoic acid from ethanol. Explain why.
(2)
This is a question about the hydrolysis of halogenoalkanes.
Devise an experiment, giving outline details only, that would enable the relative rates of hydrolysis of halogenoalkanes to be compared.
(5)
Explain the trend in the rates of hydrolysis of 1-chlorobutane, 1-bromobutane and 1-iodobutane.
(2)
The product of the hydrolysis of 2-bromobutane is butan-2-ol. Both molecules are chiral.
State what is meant by the term chiral, using three-dimensional diagrams of the enantiomers of butan-2-ol to illustrate your answer.
(3)
*(d) Compare and contrast the mechanism of hydrolysis, using aqueous potassium hydroxide, of the primary halogenoalkane, RCH2X, with that of the tertiary halogenoalkane, R3CX. Include diagrams of any intermediate or transition state.
Curly arrows are not required.
(6)
Phenylethene, commonly known as styrene, is an important substance in the production of polystyrene which is used for some types of plastic packaging. Phenylethene can be made from benzene in a three-step synthesis.
Some of the following compounds can be used to make phenylethene from benzene.
Selecting only from these compounds, devise a synthetic pathway for converting benzene into phenylethene, clearly identifying compounds A and B and stating the appropriate conditions for each step.
(5)
Which reagent could produce a diol from phenylethene?
(1)
Draw a section of the polymer, polystyrene, showing two repeat units.
(1)
Give one advantage and one disadvantage of the disposal of polystyrene by incineration.
(2)
Calculate the percentage by mass of carbon in phenylethene, giving your answer to an appropriate number of significant figures.
(2)
Phenol is a feedstock in the production of many organic molecules.
Phenol reacts with bromine water.
Complete the equation for the reaction of phenol with excess bromine water, using the skeletal formula of the organic product.
(2)
Compare and contrast the bromination of phenol with the bromination of benzene.
(3)
Phenol can be nitrated to produce 4-nitrophenol.
The mechanisms of the nitration of phenol and of benzene are similar. Complete the diagram, using curly arrows, to show a possible mechanism for the reaction between the electrophile, NO2+, and phenol to produce 4-nitrophenol.
(3)
What is the mass, in grams, of 4-nitrophenol produced from 0.94 g of phenol if the yield of this isomer is 15%?
(1)
Draw two structural isomers of 4-nitrophenol which have a benzene ring.
(1)
This question is about the reaction kinetics of an ‘iodine clock’ reaction.
One example of an ‘iodine clock’ reaction that involves the iodate(V) ions and iodide ions in acidic solution is
State why the order of reaction with respect to iodide ions cannot be five, even though 5 mol of iodide ions are shown in the equation.
(1)
A series of experiments was carried out by a student to determine the order of reaction with respect to iodate(V) ions. The concentrations of the iodide ions and the acid were in large excess and the volume of the iodate(V) solution was varied. The total volume of the reaction mixture was kept constant by the addition of suitable volumes of deionised water. The following results were obtained:
| Experiment Number | 1 | 2 | 3 | 4 | 5 | 6 |
| Volume of iodate(V) solution / cm3 | 10.0 | 7.0 | 5.0 | 3.0 | 2.0 | 1.0 |
| Time (t) / s | 180 | 260 | 357 | 606 | 900 | 800 |
| (1000/t) / s−1 | 5.56 | 1.11 | 1.25 |
In experiment 6, the student forgot to add deionised water to keep the total volume the same for each experiment. State why the total volume should be kept the same.
(1)
Complete the table and use the results from experiments 1, 2, 3, 4 and 5 to plot a graph of 1000/t against volume of iodate(V) ions.
(4)
Deduce the order of reaction with respect to the iodate(V) ions. Justify your answer.
(2)
A different version of the ‘iodine clock’ reaction involves mixing hydrogen peroxide with aqueous solutions of potassium iodide, sodium thiosulfate and starch.
The main reaction is
The reaction is first order with respect to hydrogen peroxide and iodide ions but zero order with respect to hydrogen ions.
In one experiment, the following data were obtained:
| Reactants | Initial concentration / mol dm−3 |
| H2O2(aq) | 1.50 × 10−3 |
| I−(aq) | 2.10 × 10−3 |
| H+(aq) | 2.10 × 10−3 |
Initial rate = 1.24 × 10−3mol dm−3s−1
Write the rate equation and hence deduce the value of the rate constant, k, from these data. Include units and give your answer to an appropriate number of significant figures.
(2)
Explain the purpose of the starch present in the reaction mixture when starch is neither in the rate equation, nor in the reaction equation.
(2)
Another ‘iodine clock’ reaction produced data that enabled the following graph of ln k against 1/ T to be drawn.
The Arrhenius equation can be expressed as
From the gradient of the graph, determine the activation energy, Ea, for this reaction.
Include a sign and units in your answer.
(3)
Give a reason for the point at ln k = −7 not being included in the line drawn on the graph.
(1)
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