OCR A Level Chemistry A Periodic table, elements and physical chemistry June 2019 question paper H432/01

In the diagrams below, each box represents an orbital and each electron is shown as an arrow.

Which diagram shows the correct arrangement of electrons in an atom of carbon?

Your answer

Which statement about the reactions of halogens with halide ions is correct?

A I₂(aq) can oxidise Br⁻(aq).

B Cl₂(aq) can reduce Br⁻(aq).

C Br⁻(aq) can reduce Cl₂(aq).

D Cl⁻(aq) can oxidise I₂(aq).

Your answer

One molecule of a gas has a mass of 2.658 × 10⁻²³ g.

What is a possible formula of the gas?

A CH₄

B O₂

C SO₂

D SO₃

Your answer

In the laboratory, acid spills can be cleaned up and made safe by spreading anhydrous sodium carbonate over the spill to neutralise the acid.

A student accidentally spills 50.0 cm³ of 2.00 mol dm⁻³ HCl (aq) on the bench.

What is the minimum mass of anhydrous sodium carbonate required to neutralise the acid?

A 4.15 g

B 5.30 g

C 8.30 g

D 10.6 g

Your answer

What is the oxidation number of N in Mg(NO₂)₂•3H₂O?

A +2

B +3

C +4

D +5

Your answer

Which reaction is a redox reaction?

A NaCl + AgNO₃ AgCl + NaNO₃

Your answer

Which set of elements in the solid state contain a simple molecular lattice, a giant covalent lattice and a giant metallic lattice?

A S, Si, A l

B P, Si, C

C S, P, Si

D Mg, P, S

Your answer

3.528 g of a Group 2 metal, M, is reacted with an excess of chlorine. The reaction forms 9.775 g of a chloride.

What is metal M ?

A magnesium

B calcium

C strontium

D barium

Your answer

Which statement is not correct for Group 2 hydroxides?

A Mg(OH)₂ can be used to treat indigestion.

B Ca(OH)₂ is used in agriculture to neutralise alkaline soils.

C The anion in Sr(OH)₂ contains 10 electrons.

D Ba(OH)₂ is a product from the reaction of barium and water.

Your answer

Radical reactions are responsible for the catalysed breakdown of the ozone layer.

The overall equation is shown below.

The molar gas volume in the ozone layer is approximately 2.5 m³ mol⁻¹.

What is the energy released, in kJ, during the breakdown of 1.0 m³ of ozone in the ozone layer?

A 56.8

B 113.6

C 355

D 710

Your answer

A graph of ln k against Tin K) for a reaction has a gradient with the numerical value of −4420. What is the activation energy, in kJ mol⁻¹, for this reaction?

A −532

B −36.7

C +36.7

D +5.32 × 10⁵

Your answer

The equation shows the dissociation of the acid H₃AsO₄ in water.

Which pair is a conjugate acid–base pair?

A H₃AsO₄ and H₂O

B H₂AsO₄⁻ and H₃O⁺

C H₃AsO₄ and H₃O⁺

D H₃O⁺ and H₂O

Your answer

What is the number of stereoisomers that Ni(H₂NCH₂CH₂NH₂)₂Cl₂ can form?

A 2

B 3

C 4

D 6

Your answer

Which property/properties is/are correct for a transition element?

1 The element has atoms with a partially filled d sub-shell.

2 The existence of more than one oxidation state in its compounds.

3 The formation of coloured ions.

A 1, 2 and 3

B Only 1 and 2

C Only 2 and 3

D Only 1

Your answer

Sir Humphry Davy discovered several elements including sodium, potassium, magnesium, calcium and strontium.

Explain which block in the Periodic Table sodium and magnesium belong to.

A sample of magnesium, A_r= 24.305, is found to consist of three isotopes. The accurate relative isotopic masses and % abundances of two of the isotopes are shown in the table.

Determine the relative isotopic mass of the third isotope of magnesium in the sample.

Give your answer to 5 significant figures.

A student adds an excess of calcium oxide to water in a test tube. In a separate test tube, the student adds an excess of strontium oxide to water.

Write the equation for the reaction of calcium oxide with water.

State symbols are not required.

Suggest the approximate pH of the two solutions formed in the test tubes.

pH with calcium oxide........

pH with strontium oxide........

The table below shows enthalpy changes involving potassium, oxygen and potassium oxide,

The incomplete Born–Haber cycle below can be used to determine the lattice enthalpy of potassium oxide.

In the boxes, complete the species present in the cycle. Include state symbols for the species.

Calculate the lattice enthalpy of potassium oxide.

lattice enthalpy =........ kJ mol⁻¹

A similar Born–Haber cycle to potassium oxide in (d) can be constructed for sodium oxide.

The first ionisation energy of sodium is more endothermic than that of potassium.

Explain why.

The lattice enthalpy of sodium oxide is more exothermic than that of potassium oxide.

Explain why.

Healthy human blood needs to be maintained at a pH of 7.40 for the body to function normally.

Red blood cells contain haemoglobin.

Explain using ligand substitutions:

• how haemoglobin transports oxygen around the body

• why carbon monoxide is toxic.

This question is about reactions of ions and compounds of transition elements.

A student carries out two experiments on a solution containing [Cr(H₂O)₆]³⁺(aq).

Experiment 1 The student adds an excess of aqueous ammonia to a solution containing [Cr(H₂O)₆]³⁺ until a purple solution is formed.

Experiment 2 The student carries out the following reaction sequence.

Step 1 NaOH(aq) is added slowly to a solution containing [Cr(H₂O)₆]³⁺(aq) in a boiling tube. A grey–green precipitate forms.

Step 2 An excess of NaOH(aq) is added to the boiling tube. The precipitate dissolves and a green solution forms containing a 6 coordinate complex ion.

Step 3 H₂O₂ is added to the mixture and the boiling tube is heated. A yellow solution forms.

Step 4 The solution in the boiling tube is acidified. The solution now contains Cr₂O₇²⁻(aq).

What is the formula of the complex ion in the purple solution that forms in Experiment 1

Suggest an equation for the reaction in Experiment 2, Step 1. Include state symbols.

Draw a 3-D diagram for the shape of the complex ion that forms in Experiment 2, Step 2 Include the charge of the ion.

What is the formula of the ion that causes the yellow colour in Experiment 2, Step 3

State the colour of the solution that forms in Experiment 2, Step 4.

Vanadium ions have four common oxidation states. Table 18.1 shows the colours of the ions in aqueous solution.

Complete the electron configuration of a V³⁺ ion.

The student adds excess iron to a solution containing VO²⁺(aq) ions, and observes that the colour of the solution changes from blue to green and then to violet.

Use the relevant standard electrode potentials shown in Table 18.2 to explain these observations.

Construct an equation for the first colour change from blue to green.

Iron(II) gluconate, C₁₂H₂₂FeO₁₄, is the active ingredient in some brands of iron supplements.

A student carries out an experiment to determine the mass of iron(II) gluconate in one tablet of an iron supplement, using the method below.

Stage 1 The student crushes two tablets and dissolves the powdered tablets in dilute sulfuric acid.

Stage 2 The student makes up the solution from Stage 1 to 250.0 cm³ in a volumetric flask.

Stage 3 The student then titrates 25.0 cm³ portions of the solution obtained in Stage 2 with 0.00200 mol dm⁻³ potassium manganate(VII).

The student obtains a mean titre of 13.50 cm³.

In this titration, 1 mol of manganate(VII) ions reacts with 5 mol of iron(II) ions.

Explain why the student used 0.00200 mol dm⁻³ potassium manganate(VII) solution for this titration, rather than the more usual concentration of 0.0200 mol dm⁻³ used in manganate(VII) titrations.

Use the student’s results to determine the mass, in mg, of iron(II) gluconate in one tablet.

Give your answer to 3 significant figures.

Sulfuric acid is an important chemical used to make detergents, fertilisers and dyes. It is manufactured in a multi-step process.

In the first step of the manufacture of sulfuric acid, sulfur dioxide, SO₂, can be made from the combustion of hydrogen sulfide, H₂S, shown in Reaction 1.

Explain why the enthalpy change for Reaction 1 has a negative value.

Use ideas about enthalpy changes associated with bond breaking and bond making.

Some standard entropy values are given below.

Substance	H2S(g)	O2(g)	SO2(g)	H2O(l)
S / J K−1 mol−1	206	205	248	70

Using calculations, explain whether Reaction 1 is feasible at 20 °C.

Calculations

Explanation for feasible or non feasible........

Write an expression for K_p for Equilibrium 1.

Include the units.

Determine the value of K_p for Equilibrium 1 at 1000 K.

Show all your working.

Give your answer to 3 significant figures.

The chemist repeats the experiment in (b) at a different temperature.

The chemist finds that the value of K_p is greater than the answer to (b)(ii).

Explain whether the temperature in the second experiment is higher or lower than 1000 K.

Vanadium(V) oxide, V₂O₅(s), is used as a catalyst in equilibrium 1.

Explain whether vanadium(V) oxide is acting as a homogeneous or heterogeneous catalyst.

This question is about weak acids.

The K_a values of three weak acids are shown in Table 20.1.

Calculate the pH of 0.0800 mol dm⁻³ C₂H₅COOH(aq).

Give your answer to 2 decimal places.

Show by calculation that 20.0 cm³ of NaOH(aq) is required to reach the end point.

Calculate the pH of the final solution.

Give your answer to 2 decimal places.

On the axes below, sketch a pH curve for the pH changes during the addition of 45.0 cm³ of 0.100 mol dm⁻³ NaOH(aq) to 25.0 cm³ of 0.0800 mol dm⁻³ C₂H₅COOH(aq).

The student considers using the four indicators in Table 20.2 for the titration.

Explain which indicator would be most suitable for the titration.

The student repeats the experiment starting with 25.0 cm³ of 0.0800 mol dm⁻³ HCN(aq) and adding a total of 45.0 cm³ of 0.100 mol dm⁻³ NaOH(aq).

Predict one similarity and one difference between the pH curve with C₂H₅COOH(aq) and the pH curve with HCN(aq). Use the information in Table 20.1, and your answer to (b)(iii).

Similarity........

Difference........

The student calculates the pH of 0.0800 mol dm⁻³ HIO₃(aq). The student assumes that the equilibrium concentration of HIO₃(aq) is the same as the initial concentration of HIO₃(aq).

The student measures the pH, and finds that the measured pH value is different from the calculated pH value.

Explain why the measured pH is different from the calculated pH.