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OCR A Level Chemistry

Topic questions Energy changes Born-Haber cycles and lattice enthalpy

Born-Haber cycles and lattice enthalpy

6 questions · 45 marks · about 1 hour

Born-Haber cycles and lattice enthalpy questions

TopicBorn-Haber cycles and lattice enthalpy

OCR H432 Born-Haber cycles and lattice enthalpy 6 questions

Periodic table, elements and physical chemistry June 2024, Question 16 17 marks

This question is about energy changes.

Hydrogen peroxide decomposes as shown in Reaction 16.1.

Question 16, shown as an image
(a)

The table shows enthalpy changes of formation and entropies.

Hf / kJ mol–1S / J K–1 mol–1
H2O2(l)–188110
H2O(l)–28670.0
O2(g)0205
(a)(i)

Calculate the free-energy change, maths symbolG, in kJ mol–1, of Reaction 16.1 at 25 maths symbolC.

Give your answer to 3 significant figures.

maths symbolG =........ kJ mol–1

[4]
Reveal mark scheme Mark scheme for question 16(a)(i)
(a)(ii)

The decomposition of hydrogen peroxide shown in Reaction 16.1 is feasible.

Suggest why Reaction 16.1 does not take place at 25 maths symbolC despite being feasible.

[1]
Reveal mark scheme Mark scheme for question 16(a)(ii)
(b)

The rate of decomposition of hydrogen peroxide shown in Reaction 16.1 can be increased by adding a small amount of powdered manganese(IV) oxide, MnO2.

The MnO2 acts as a catalyst.

(b)(i)

Complete the enthalpy profile diagram for Reaction 16.1 using formulae for the reactants and products.

• Use Ea to label the activation energy without MnO2.

• Use Ec to label the activation energy with MnO2.

• Use maths symbolH to label the enthalpy change of reaction.

Figure for question 16
[3]
Reveal mark scheme Mark scheme for question 16(b)(i)
(b)(ii)

Explain why MnO2 is described as a heterogeneous catalyst for this reaction.

[1]
Reveal mark scheme Mark scheme for question 16(b)(ii)
(b)(iii)

Mn3O4 is a compound in which Mn has two different oxidation states. The two oxidation states are different from the Mn in MnO2.

Suggest the two oxidation states of manganese in Mn3O4.

[1]
Reveal mark scheme Mark scheme for question 16(b)(iii)
(c)
Figure for question 16
(c)(i)

Define the term lattice enthalpy.

[2]
Reveal mark scheme Mark scheme for question 16(c)(i)
(c)(ii)
Figure for question 16
[3]
Reveal mark scheme Mark scheme for question 16(c)(ii)
(c)(iii)

Calculate the lattice enthalpy of MnO.

lattice enthalpy =........ kJ mol–1

[2]
Reveal mark scheme Mark scheme for question 16(c)(iii)

Periodic table, elements and physical chemistry June 2023, Question 16 10 marks

This question is about energy changes.

(a)

Lattice enthalpies can be determined indirectly using Born-Haber cycles.

The table below shows the energy changes that are needed to determine the lattice enthalpy of barium iodide, BaI2.

Figure for question 16
(a)(i)

The diagram below shows an incomplete Born-Haber cycle that can be used to calculate the lattice enthalpy of barium iodide.

On the dotted lines, add the species present, including state symbols.

Ba2+(g) + 2I(g) + 2e–

Figure for question 16
[4]
Reveal mark scheme Mark scheme for question 16(a)(i)
(a)(ii)

Calculate the lattice enthalpy of barium iodide.

lattice enthalpy =........ kJ mol–1

[2]
Reveal mark scheme Mark scheme for question 16(a)(ii)
(b)

The first and second ionisation energies of magnesium, Mg, and strontium, Sr, in Group 2 are given in the table below.

ElementFirst ionisation energy / kJ mol–1Second ionisation energy / kJ mol–1
Mg+738+1451
Sr+550+1064

• Explain why the first ionisation energy of Mg is greater than the first ionisation energy of Sr.

• Explain why the second ionisation energy of Sr is greater than the first ionisation energy of Sr.

[4]
Reveal mark scheme Mark scheme for question 16(b)

Periodic table, elements and physical chemistry June 2019, Question 16 15 marks

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

(a)

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

[1]
Reveal mark scheme Mark scheme for question 16(a)
(b)

A sample of magnesium, Ar= 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.

IsotopeRelative isotopic mass% abundance
24 Mg23.98578.99%
25 Mg24.98610.00%

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

Give your answer to 5 significant figures.

[2]
Reveal mark scheme Mark scheme for question 16(b)
(c)

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.

(c)(i)

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

State symbols are not required.

[1]
Reveal mark scheme Mark scheme for question 16(c)(i)
(c)(ii)

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

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

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

[1]
Reveal mark scheme Mark scheme for question 16(c)(ii)
(d)

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

Figure for question 16
(d)(i)

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.

Figure for question 16
[4]
Reveal mark scheme Mark scheme for question 16(d)(i)
(d)(ii)

Calculate the lattice enthalpy of potassium oxide.

lattice enthalpy =........ kJ mol−1

[2]
Reveal mark scheme Mark scheme for question 16(d)(ii)
(e)

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

(e)(i)

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

Explain why.

[2]
Reveal mark scheme Mark scheme for question 16(e)(i)
(e)(ii)

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

Explain why.

[2]
Reveal mark scheme Mark scheme for question 16(e)(ii)

Periodic table, elements and physical chemistry June 2018, Question 13 1 mark

Which enthalpy change(s) is/are endothermic?

1 The bond enthalpy of the C–H bond

2 The second electron affinity of oxygen

3 The standard enthalpy change of formation of magnesium

A 1, 2 and 3

B Only 1 and 2

C Only 2 and 3

D Only 1

Your answer

[1]
Reveal mark scheme Mark scheme for question 13

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