The reaction p4 +502p4010 + 712 kcal is
1)absorbing energy
2)endothermic
3)not reacting
4)exothermic

The reaction is exothermic (option 4)

Explanation:

P4 + 5O2 → P4O10 + 712 kcal

In chemical reactions heat can be absorbed or released:

⇒in the first case, when heat is absorbed, this is called an endothermic reaction. The products have more energy than the reactants. The reaction requires or absorbs energy from it's surroundings.  That means  that in this reaction energy , in the form of heat, will be absorbed by the reactants.

⇒ when heat is released, this is called an exothermic reaction. The reactants have more energy than the products. The reaction gives or releases energy to it's surroundings.  That means  that in this reaction energy , in the form of heat, will be released by the reactants.

in the case of P4 + 5O2 → P4O10 + 712 kcal

We notice that on the right side, which is the product side, there is a positive amount of energy. This means that the energy is released by the the reactants, in this reaction. The reaction is exothermic.

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4) exothermic

Explanation:

If the reaction has negative ∆H value then the reaction is exothermic

If the reaction has positive ∆H value then the reaction is endothermic

When  Heat energy is given in the equation itself

If it is present on the left side it means that heat is absorbed and the reaction is Endothermic

If it is present on the right side it means heat is given off and the reaction is exothermic

So here we see  

Heat energy is present in the equation on the right side so 712 kcal heat is released and the reaction is EXOTHERMIC

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