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    Why are reversible reactions both endothermic and exothermic? I can't grab hold of this concept.

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    Endotherimic means that a reaction between 2 or more substances 'takes in' thermal energy as the chemical reaction takes place.
    Exothermic means that the reaction "gives out" thermal energy.
    Thermal energy means heat.
    Therefore a reversible reaction means that the reaction between the two or more chemicals both absorbs (takes in) and emits (gives out) heat. Reversible means that a reaction can do two things.
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    (Original post by Federerr)
    Why are reversible reactions both endothermic and exothermic? I can't grab hold of this concept.

    Thanks.
    When a reaction is reversible it can go forwards and backwards. So if a forward reaction is endothermic the backward reaction MUST be endothermic because it is reversing the exothermic reaction.
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    (Original post by Federerr)
    Why are reversible reactions both endothermic and exothermic? I can't grab hold of this concept.

    Thanks.
    In reversible reactions, both a forward and a back reaction exist. To let reactants react to a product (forward reaction), a certain amount of (thermal) energy has to be spent (endothermic reaction), after that the reactants beginning to react to the product. During and up to the end of this reaction, energy is released (exothermic reaction).

    To get the reactants back by the product (back reaction), energy has to be spent again. Without that energy, the product cannot be 'divided' in the reactants.
 
 
 
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