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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Knowledge Check

For endothermic reaction which is correct?

A

`H_p gt H_r`

B

`H_p lt H_r`

C

H_p=H_r

D

sign of `Delta H` is negative

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