Adding heat to exothermic reactions

[reising1]

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Exothermic reactions take the form

R --> P + heat (this is an equilibrium even though I've drawn 1 arrow)

Now, what happens when heat is added to the reaction? Is the newly added heat considered a reactant or product? Do more products get made or reactants?

 

[navho77]

Exothermic reactions take the form

R --> P + heat (this is an equilibrium even though I've drawn 1 arrow)

Now, what happens when heat is added to the reaction? Is the newly added heat considered a reactant or product? Do more products get made or reactants?

Heat is considered a product. Adding heat will shift the equilibrium to the reactant side.

 

[reising1]

Heat is considered a product. Adding heat will shift the equilibrium to the reactant side.

But doesn't it technically act as a reactant and a product if it's added to a beaker, for example, that has a reaction underway?

 

[navho77]

But doesn't it technically act as a reactant and a product if it's added to a beaker, for example, that has a reaction underway?

No, it is not considered a reactant just because you add it into the system. Something is only considered a reactant if it is required to get products that weren't there at the beginning of the reaction. If the reaction is exothermic, the net heat (meaning after you've crossed the reaction barrier to reach the activated state) lies on the product side. The terms reactant and product have only to do with their thermodynamic role, not the way in which they are introduced to where the reaction is happening.

It can get confusing because heating a reaction increases the rate of the reaction, but that says noting about the equilibrium. The rate is a kinetic characteristic, while the equilibrium condition is a thermodynamic condition.