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Edexcel IGCSE Chemistry 3.7C Bond energies to calculate the enthalpy change

Practise using bond energy tables and balanced equations to find energy broken, energy formed and the sign of ΔH in kJ/mol.

Syllabus
First assessment 2019
Course
Chemistry 4CH1

Exam points

  • calculate bonds broken and bonds formed from displayed formulae and bond energy tables
  • apply ΔH = energy in bonds broken - energy in bonds formed, including the sign
  • rearrange a bond energy calculation to find an unknown C-Cl or similar bond value

3.7C Bond energies to calculate the enthalpy change question 1

[Maximum number: 3]

Gaseous ethanol is manufactured by reacting ethene gas with steam.

This is the equation for the reaction.

The equation shows the displayed formulae for the reactants and products.

Figure for Question 3.7C Bond energies to calculate the enthalpy change question 1 — Edexcel IGCSE Chemistry

The table gives the bond energies.

Table for Question 3.7C Bond energies to calculate the enthalpy change question 1 — Edexcel IGCSE Chemistry

Using the data in the table and the equation, show that the enthalpy change, ΔH\Delta H, is approximately −40 kJ/mol-40 \mathrm{~kJ} / \mathrm{mol}.

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