AQA A Level Chemistry Paper 3 November 2020 question paper 7405/3

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.

This question is about oxides.

Sodium oxide forms a solution with a higher pH than magnesium oxide when equal amounts, in moles, of each oxide are added separately to equal volumes of water.

State why both oxides form alkaline solutions.

Suggest why sodium oxide forms a solution with a higher pH than the solution formed from magnesium oxide.

Give an equation for the reaction between phosphorus(V) oxide and water.

In the Contact process, sulfur(IV) oxide is converted into sulfur(VI) oxide using vanadium(V) oxide as a catalyst.

Give two equations to show how the vanadium(V) oxide acts as a catalyst in this process.

Explain why complexes formed from transition metal ions are coloured.

The iron content of iron tablets can be determined by colorimetry.

Method:

• Dissolve a tablet in sulfuric acid.

• Oxidise all the iron from the tablet to Fe³⁺(aq).

• Convert the Fe³⁺(aq) into a complex that absorbs light of wavelength 490 nm

• Make the solution up to 250 cm³

• Measure the absorbance of light at 490 nm with a colorimeter.

• Use a calibration graph to find the concentration of the iron(III) complex.

Calculate the energy, in J, gained by each excited electron in the absorption at 490 nm

Energy gained by each electron
J

Describe how a calibration graph is produced and used to find the concentration of the iron(III) complex.

The concentration of iron(III) in the solution is 4.66 x 10^–3 mol dm^–3

Calculate the mass, in mg, of iron in the tablet used to make the 250 cm³ of solution.

Mass of iron in the tablet
mg

Cisplatin, [Pt(NH₃)₂Cl₂], is used as an anti-cancer drug.

Cisplatin works by causing the death of rapidly dividing cells.

Name the process that is prevented by cisplatin during cell division.

After cisplatin enters a cell, one of the chloride ligands is replaced by a water molecule to form a complex ion, B.

Give the equation for this reaction.

When the complex ion B reacts with DNA, the water molecule is replaced as a bond forms between platinum and a nitrogen atom in a guanine nucleotide. The remaining chloride ligand is also replaced as a bond forms between platinum and a nitrogen atom in another guanine nucleotide.

Figure 1 represents two adjacent guanine nucleotides in DNA.

Complete Figure 1 to show how the platinum complex forms a cross-link between the guanine nucleotides.

An experiment is done to investigate the rate of reaction in Question 04.2.

During the experiment the concentration of cisplatin is measured at one-minute intervals.

Explain how graphical methods can be used to process the measured results, to confirm that the reaction is first order.

In another experiment, the effect of temperature on the rate of the reaction in Question 04.2 is investigated.

Table 1 shows the results.

Complete Table 1.

The Arrhenius equation can be written in the form

Use the data in Table 1 to plot a graph of ln k against on the grid in Figure 2. Calculate the activation energy, E_a, in kJ mol¹

The gas constant, R = 8.31 J K¹ mol¹

A bomb calorimeter can be used for accurate determination of the heat change during combustion of a fuel.

A bomb calorimeter is a container of fixed volume that withstands the change in pressure during the reaction.

The fuel is mixed with pure oxygen in the calorimeter, ignited and the temperature change is recorded.

The total heat capacity (C_cal) of the calorimeter is calculated using a fuel for which the heat change is known.

In an experiment to calculate C_cal, 2.00 g of hexane (M_r = 86.0) is ignited. A temperature change (T) of 12.4 °C is recorded.

Under the conditions of the experiment, 1.00 mol of hexane releases 4154 kJ of energy when combusted.

The heat energy released in the calorimeter, q = C_calT

Calculate the heat capacity (C_cal) in kJ K¹

When the experiment is repeated with 2.00 g of octane (M_r = 114.0) the temperature change recorded is 12.2 °C

Calculate the heat change, in kJ mol¹, for octane in this combustion reaction.

If you were unable to calculate a value for C_cal in Question 05.1, use 6.52 kJ K¹ (this is not the correct value).

State why the heat change calculated from the bomb calorimeter experiment is not an enthalpy change.

The thermometer used to measure the temperature change of 12.2 °C in Question 05.2 has an uncertainty of 0.1 °C in each reading.

Calculate the percentage uncertainty in this use of the thermometer.

Suggest one change to this experiment that decreases the percentage uncertainty while using the same thermometer.

Standard electrode potentials are measured by comparison with the standard hydrogen electrode.

State the substances and conditions needed in a standard hydrogen electrode.

It is difficult to ensure consistency with the setup of a standard hydrogen electrode. A Cu²⁺(aq) /Cu(s) electrode ( = +0.34 V) can be used as a secondary standard.

A student does an experiment to measure the standard electrode potential for the TiO²⁺(aq)/Ti(s) electrode using the Cu²⁺(aq)/ Cu(s) electrode as a secondary standard.

A suitable solution containing the acidified TiO²⁺(aq) ion is formed when titanium(IV) oxysulfate (TiOSO₄) is dissolved in 0.50 mol dm³ sulfuric acid to make 50 cm³ of solution.

Describe an experiment the student does to show that the standard electrode potential for the TiO²⁺(aq) /Ti(s) electrode is 0.88 V

The student is provided with:

• the Cu²⁺(aq)/ Cu(s) electrode set up ready to use

• solid titanium(IV) oxysulfate (M_r = 159.9)

• 0.50 mol dm³ sulfuric acid

• a strip of titanium

• laboratory apparatus and chemicals.

Your answer should include details of:

• how to prepare the solution of acidified TiO²⁺(aq)

• how to connect the electrodes

• measurements taken

• how the measurements should be used to calculate the standard electrode potential for the TiO²⁺(aq)/Ti(s) electrode.

Give the half-equation for the electrode reaction in the TiO²⁺(aq)/Ti(s) electrode in acidic conditions.

Table 2 shows some electrode potential data.

Use the data in Table 2 to explain why copper does not react with most acids but does react with nitric acid.

Give an equation for the reaction between copper and nitric acid.

Equation

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

Which has a bond angle of 109.5°?

Which reaction has an enthalpy change equal to the standard enthalpy of formation of silver iodide?

In which conversion is the metal reduced?

The rate expression for the reaction between X and Y is

Which statement is correct?

Which statement about pH is correct?

A 0.10 mol dm^–3 aqueous solution of an acid is added slowly to 25 cm³ of a 0.10 mol dm^–3 aqueous solution of a base.

Which acid–base pair has the highest pH at the equivalence point?

In the test for a halide ion in aqueous solution, dilute nitric acid is added before the addition of silver nitrate solution.

Why is nitric acid added?

Which shows the major product(s) formed when chlorine reacts with cold, dilute, aqueous sodium hydroxide?

Which shows the electron configuration of an atom of a transition metal?

Which will not act as a ligand in the formation of a complex ion?

Which shows the correct oxidation state and co-ordination number of cobalt in

Which statement is not correct?

Which compound decolourises acidified potassium manganate(VII) solution?

Which has E - Z isomers?

Which is the mechanism for this conversion?

Which compound decolourises bromine water in the absence of sunlight?

Which compound reacts to form a ketone when warmed with an acidified solution of potassium dichromate(VI)?

Which does not contain an asymmetric carbon atom?

Which reaction involves addition-elimination?

Which compound reacts with hydrogen bromide to give 2-bromo-3-methylbutane as the major product?

Which forms a polymer with ClOC(CH₂)₈COCl?

Which structure shows the zwitterion of an amino acid?

What is the minimum volume, in cm³, of 0.02 mol dm^–3 KMnO₄ solution needed to

Which is the concentration of NaOH(aq), in mol dm^–3, that has pH = 14.30?

What are the units of the rate constant for a third order reaction?

What is the pH of 0.015 mol dm^–3 sulfuric acid?

Which compound is formed when phenyl benzenecarboxylate is hydrolysed under acidic conditions?

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?