2 Answers

Rajagopalx · Answer 1 · 2018-05-27T22:02:34+0000

Answer : The reactions that are exothermic have
$\Delta H_f$ values that are negative.

Explanation :

Exothermic reaction : When system releases heat energy to surrounding is known as exothermic reaction.

Endothermic reaction : When system absorbs heat energy from surrounding is known as endothermic reaction.

Enthalpy of reaction,
$(\Delta H)$ : It is defined as the heat energy changes when the reactants go to the products.

If the heat energy is released then the reaction is exothermic and the
$(\Delta H)$ is negative that means product is more stable than the reactant.

If the heat energy is absorbed then the reaction is endothermic and the
$(\Delta H)$ is positive that means product is less stable than the reactant.

Hence, the reactions that are exothermic have
$\Delta H_f$ values that are negative.

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