State which of the following processes is endothermic and which is exothermic.

CHEMISTRY · Multi-part · A Level · Chemistry · Energetics · Energetics

Problem

State which of the following processes is endothermic and which is exothermic. (a) (i) The breaking of a chemical bond. (ii) The forming of a chemical bond. (b) The table below shows bond-energy data for covalent bonds. (i) Use the information given in the table to calculate the overall enthalpy change for the combustion of ethanol producing carbon dioxide and water. (ii) Is the process in (i) endothermic or exothermic?

Bond	Bond energy/ $\mathrm{kJ\,mol^{-1}}$
$\mathrm{C-H}$	$435$
$\mathrm{O=O}$	$497$
$\mathrm{C=O}$	$803$
$\mathrm{H-O}$	$464$
$\mathrm{C-C}$	$347$
$\mathrm{C-O}$	$358$

Related theory

Thermodynamics
Types of enthalpy
Enthalpy Changes of Reactions
Bond Enthalpies

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