Energetics (Edexcel International A Level Chemistry)

Exam Questions

11 mark

The enthalpy change of solution of sodium sulfate, Na2SO4 , may be calculated using three pieces of data. Which of these pieces of data is not required?

  • lattice energy of Na2SO4

  • enthalpy change of hydration of Na+

  • enthalpy change of formation of Na2SO4

  • enthalpy change of hydration of begin mathsize 14px style S O subscript 4 to the power of 2 minus sign end style

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1a1 mark

A simplified Born-Haber cycle for the formation of lithium iodide is shown.

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a)

The enthalpy change of atomisation of iodine (+107 kJ mol–1) is given by the equation

  •  1⁄2I2(g) → I(g)

  • 1⁄2I2(s) → I(g)

  • I2(g) → 2I(g)

  •  I2(s) → 2I(g)

1b
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1 mark
b)
Use the information in the cycle to calculate the electron affinity of iodine.

  • –298 kJ mol–1

  • –242 kJ mol–1

  • +242 kJ mol–1

  • +298 kJ mol–1

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2a1 mark

This question is about four ionic compounds.

a)
Which of these compounds would be expected to have the least exothermic lattice energy?
  • calcium chloride

  • magnesium chloride

  • potassium bromide

  • sodium bromide

2b1 mark
b)
Which of these compounds would be expected to have the largest difference between their experimental (Born–Haber) and theoretical lattice energies?
  • calcium chloride

  • magnesium chloride

  • potassium bromide

  • sodium bromide

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3a1 mark

The diagram shows the Born-Haber cycle for magnesium chloride.

q7-paper-4-oct-2021-edexcel-ial-chemistry

a)
Which of these is the electron affinity of chlorine?
  • y

  • y/2

  • (w + y)

  • (w + y)/2   

3b1 mark
b)
Which expression gives the lattice energy (LE) for magnesium chloride?
  • LE = u − (v + w + x + y)

  • LE = v + w + x + y − u

  • LE = y − u − (v + w + x)

  • LE = v + w + x − y + u

3c1 mark
c)
Which energy change in the cycle does x represent?
  • the first ionisation energy of magnesium

  • the second ionisation energy of magnesium

  • the sum of the first and second ionisation energies of magnesium

  • the sum of the enthalpy change of atomisation and the first and second ionisation energies of magnesium

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1
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Some energy changes are given in the table.

Energy change Value / kJ mol–1
Lattice energy for CaCl2(s) –2258
Enthalpy change of solution of CaCl2(s) –120
Enthalpy change of hydration of Cl(g) –364


Use these data to calculate the enthalpy change of hydration of Ca2+(g).

  • –1410 kJ mol–1

  • –1650 kJ mol–1

  • –2014 kJ mol–1

  • –3106 kJ mol–1

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