NotesAcademy | Chemistry | Chemical Energetics
Chemical Energetics
Types of Energy Conversion
There are different types of energy conversion, namely chemical reactions
involving heat/light change/electrical change and nuclear reactions. Electrical
change involves electrical cells/electrolysis.
Enthalpy Change (ΔH)
Energy that is stored in bonds is known as enthalpy. Enthalpy change, ΔH, is
defined as the amount of heat released or absorbed when a chemical reaction
occurs at a constant pressure.
Bond energy is the heat required to break one mole of molecules into their
individual atoms.
ΔH = Hp – Hr
ΔH = bond breaking – bond making
Hr = enthalpy of reactants (bond breaking)
Hp = enthalpy of products (bond making)
Energy Profile Diagrams
Activation energy of a reaction is defined as the minimum energy that must be
overcome in order for a chemical reaction to take place. It is the difference
between the energy of the reactants and the peak of the energy profile
diagram.
Breaking and Forming Bonds
Bond breaking is endothermic because heat energy must be taken in by the
reactants to overcome the existing bonds to form new products.
Bond forming is exothermic because heat energy is released when new bonds
are formed in the product.
Bond energy is the amount of energy required to make or break a chemical
bond. The stronger the bond, the higher the bond energy.
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