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Why is the sign of DeltaH negative for a...

Why is the sign of `DeltaH` negative for an exothermic reaction and why is it positive for an endothermic reaction?

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In a chemical reaction, the change in enthalpy, `DeltaH=`sum of the total enthalpies of products-Sum of the total enthalpies of reactants`=sumH_(P)-sumH_(R)`
In case of an exothermic reaction, `sumH_(P) lt sumH_(R)`, and hence `DeltaH lt 0`, while for an endothermic reaction `sumH_(P) gt sumH_(R),` resulting `Delta H gt 0`.
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