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Energetics Notes

This is a sample of our (approximately) 4 page long Energetics notes, which we sell as part of the Chemistry AS Notes collection, a A package written at Manchester High School For Girls Sixth Form in 2013 that contains (approximately) 54 pages of notes across 17 different documents.

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Energetics Revision

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Unit 2: 7 Energetics

ENERGETICS EXOTHERMIC REACTIONS release energy (heat) e.g. neutralisation reactions. ENDOTHERMIC REACTIONS take in energy (heat) e.g. decomposition reactions.


The amount of heat given out or taken in during a reaction varies with conditions. ENTHALPY CHANGE (△H) is a heat change during a reaction measured at constant pressure. Standard states under which △H is measured;

1.Standard temperature - 298K

2.Standard pressure - 100kPa

An enthalpy change carried out at standard temperature and pressure is the standard molar enthalpy change of the reaction, represented as △Hθ.
> △Hθ is measured in kJmol-1.
>The enthalpy change depends on the concentration/quantities of materials reacting and the state they are in (always use state symbols in equations)

△H = Hproducts - Hreactants

Hproducts < Hreactants : △H = -ve

Hproducts > Hreactants : △H = +ve

In the above reactions, we have assumed energy is neither created or destroyed - PRINCIPLE OF CONSERVATION OF ENERGY.



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