AQA A Level Chemistry Paper 3 June 2019 question paper 7405/3

Sodium thiosulfate reacts with dilute hydrochloric acid as shown.

Give the simplest ionic equation for this reaction.

The gas SO₂ is a pollutant.

State the property of SO₂ that causes pollution when it enters rivers.

Give an equation to show the reaction of SO₂ with water.

Draw a diagram to show the shape of a molecule of H₂O Include any lone pairs of electrons.

State the HOH bond angle.

Explain this shape and bond angle.

Diagram

The initial rate of the reaction between sodium thiosulfate and hydrochloric acid can be monitored by measuring the time taken for a fixed amount of sulfur to be produced.

Describe an experiment to investigate the effect of temperature on the initial rate of this reaction.

Include

• a brief outline of your method

• how you will measure the time taken for a fixed amount of sulfur to be formed

• how you will present your results in graphical form

• a sketch of the graph that you would expect.

This question is about sulfuric acid and its salts.

Draw the displayed formula of a molecule of H₂SO₄

In aqueous solution, sulfuric acid acts as a strong acid. The H₂SO₄ dissociates to form HSO₄ ions and H⁺ ions.

The HSO₄ ions act as a weak acid and dissociate to form SO₄² ions and H⁺ ions.

Give an equation to show each stage in the dissociation of sulfuric acid in aqueous solution.

Include appropriate arrows in your equations.

A student is required to make 250 cm³ of an aqueous solution that contains an accurately measured mass of sodium hydrogensulfate (NaHSO₄).

Describe the method that the student should use to make this solution.

A solution that contains 605 mg of NaHSO₄ in 100 cm³ of solution has a pH of 1.72

Calculate the value of K_a for the hydrogensulfate ion (HSO₄) that is behaving as a weak acid. Give your answer to three significant figures.

Some sodium sulfate is dissolved in a sample of the solution from question 02.4.

Explain why this increases the pH of the solution.

Figure 1 represents the cell used to measure the standard electrode potential for the

Name the piece of apparatus labelled A.

State the purpose of A.

Name the substance used as electrode B in Figure 1.

Complete Table 1 to identify C, D and E from Figure 1. Include the essential conditions for each.

The standard electrode potential, , for the Fe³/Fe² electrode is 0.77 V

Give the ionic equation for the overall reaction in the cell in Figure 1.

State the change that needs to be made to the apparatus in Figure 1 to allow the cell reaction to go to completion.

A student sets up a cell as shown in the cell representation.

The student measures the cell EMF, E_cell, with several different concentrations of

The results are shown in Table 2.

Complete Table 2 to show the value missing from experiment 4.

Plot a graph of E_cell against ln ([Zn²]/[Cu²]) on the grid.

This equation shows how E_cell varies with concentration for this reaction.

This equation is in the form of the equation for a straight line, y = mx + c

Calculate the gradient of your plotted line on the graph in question 03.6. You must show your working.

Use your gradient to calculate the temperature, T, at which the measurements of E_cell were taken. (If you were unable to calculate a gradient you should use the value 0.016 V This is not the correct value.)

In experiment 2 in Table 2 the electrode potential of the Cu²/Cu electrode is +0.33 V

Use data from Table 2 in question 03.6 to calculate the electrode potential for the

Give one reason why your calculated value is different from the standard electrode potential for Zn²/Zn electrode.

Ethanal reacts with potassium cyanide, followed by dilute acid, to form 2-hydroxypropanenitrile.

Name the mechanism for the reaction between potassium cyanide and ethanal.

The 2-hydroxypropanenitrile formed by the reaction in question 04.1 is a mixture of equal amounts of two isomers.

State the name of this type of mixture.

Explain how the structure of ethanal leads to the formation of two isomers.

Draw 3D representations of the two isomers to show the relationship between them.

3D representations

2-Hydroxypropanenitrile can be used in the synthesis of the monomer,

Suggest a suitable reagent and conditions for the conversion of 2-hydroxypropanenitrile into acrylonitrile.

Draw a section of the polymer polyacrylonitrile, showing three repeating units.

The percentage by mass of iron in a steel wire is determined by a student.

The student

• reacts 680 mg of the wire with an excess of sulfuric acid, so that all of the iron in the

Give the equation for the reaction between iron and sulfuric acid.

The titration results are shown in Table 3.

Calculate the mean titre.

Give the overall ionic equation for the oxidation of Fe² by manganate(VII) ions, in acidic conditions.

State the colour change seen at the end point of the titration.

Name the piece of apparatus used for these stages of the method.

Adding the potassium manganate(VII) solution

The balance used to weigh the 680 mg of iron wire has an uncertainty of ±0.005 g

A container was weighed and its mass was subtracted from the total mass of the container and wire.

Calculate the percentage uncertainty in using the balance.

Which amount of sodium hydroxide would react exactly with 7.5 g of a diprotic acid,

Lead(II) nitrate and potassium iodide react according to the equation

In an experiment, 25.0 cm³ of a 0.100 mol dm^–3 solution of each compound are mixed together.

Which amount, in mol, of lead(II) iodide is formed?

Nitrogen dioxide is produced from ammonia and air as shown in these equations

What is the enthalpy change (in kJ mol^–1) for the following reaction?

Which change leads to a higher concentration of SO₃ in this equilibrium mixture?

The results of an investigation of the reaction between P and Q are shown in this

The rate equation is: rate = k [P] [Q]²

What is the initial concentration of Q in experiment 2?

The equation for the reaction between sulfur dioxide and oxygen is shown.

In an experiment, 2.00 mol of sulfur dioxide are mixed with 2.00 mol of oxygen. The total amount of the three gases at equilibrium is 3.40 mol

What is the mole fraction of sulfur trioxide in the equilibrium mixture?

Nitrogen reacts with hydrogen in this exothermic reaction

Which change increases the equilibrium yield of ammonia but has no effect on the value of the equilibrium constant K_p?

The values for two electrodes are shown.

What is the EMF of the cell Fe(s)|Fe²⁺(aq)||Cu²⁺(aq)|Cu(s)?

Which atom has the greatest first ionisation energy?

What is the correct observation when barium metal is added to an excess of water?

An aqueous solution of a salt gives a white precipitate when mixed with aqueous silver nitrate and when mixed with dilute sulfuric acid.

Which could be the formula of the salt?

Which statement is not correct about the trends in properties of the hydrogen halides from HC l to HI ?

What is observed when concentrated hydrochloric acid is added to an aqueous solution of CuSO₄ until no further change occurs?

What is the most suitable reagent for detecting the presence of carbonate ions in the presence of an excess of sulfate ions?

Methylbenzene reacts with a mixture of concentrated nitric acid and concentrated sulfuric acid.

What is the name of the mechanism for this reaction?

A possible synthesis of a compound found in jasmine flower oil is shown.

Which mechanism is not used in this synthesis?

Which compound is formed when 1-phenylethanol reacts with acidified potassium dichromate(VI)?

Three reagents are added separately to four organic compounds.

Which row shows the correct observations?

Which compound is formed by acid hydrolysis of phenylmethyl ethanoate?

A student is required to dry a liquid sample of pentanoic acid.

Which drying agent is suitable?

The reaction between propanoyl chloride and benzene is an example of acylation.

Which is a correct representation of part of the mechanism of this reaction?

Methylamine reacts with bromoethane by substitution to produce a mixture of products.

Which compound is not a possible product of this reaction?

Which polymer has hydrogen bonding between its chains?

Which structure shows part of a peptide link in a protein?

Two strands of DNA are linked together by hydrogen bonding between bases on each strand. Which row shows the number of hydrogen bonds between the pair of bases? Use the Data Booklet to help you answer this question.

Which is not responsible for conduction of electricity?

In the UK industrial ethanol is now produced by the direct hydration of ethene. This process has largely replaced the fermentation method.

Which is a likely reason for this change of method?

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

Which compound can be purified by forming a hot aqueous solution that recrystallises on cooling?

Use the Data Booklet to help you answer this question

Which is the main aspartic acid species present in an aqueous solution at pH = 14?