Answer:
A negative ∆H indicates an exothermic reaction.
A positive ∆H indicates an endothermic reaction.
Step-by-step explanation:
Energy is the ability to perform a job or to produce heat. Chemical reactions involve a rearrangement of atoms between substances with rupture or formation of chemical bonds and this generates changes in the energy of the system.
A chemical reaction is endothermic when it absorbs energy from the environment, that is, heat is transferred from outside to inside the system. An exothermic reaction is one where energy is released from the system into the environment in the form of heat.
On the other hand the ∆H (heat of reaction) is the heat that accompanies the entire reaction, that is, it represents the heat released or absorbed during the reaction.
The enthalpy of reaction ΔH is calculated through the enthalpy difference between the products and reagents:
ΔH = ∑Hproducts - ∑Hreactants
As mentioned, a process is considered exothermic when heat is released to the surroundings. This means that the system loses heat, so ∆H <0. On the contrary, endothermic processes are characterized by absorbing heat from the surroundings, which implies that ∆H> 0.
Finally
- A negative ∆H indicates an exothermic reaction.
- A positive ∆H indicates an endothermic reaction