Negative Delta H Is Exothermic

Learn about the concept of enthalpy, exothermic, and endothermic reactions

Transcript

Breaking bonds betwixt atoms requires free energy. Creating new bonds releases it.

The enthalpy of a reaction is equal to the energy required to break the bonds between reactants minus the free energy released by the formation of new bonds in the products.

So, if a reaction releases more free energy than it absorbs, the reaction is exothermic and enthalpy will be negative.

Think of this as an amount of oestrus leaving (or being subtracted from) the reaction.

If a reaction absorbs or uses more energy than it releases, the reaction is endothermic, and enthalpy will be positive. Let's look at the enthalpy changes in the combustion of methane.

In this reaction, the bonds betwixt the hydrogens and the carbon and the bonds betwixt the oxygens are broken. Breaking these bonds requires free energy to be captivated by the reaction.

But and then, new bonds form between hydrogen and oxygen and between carbon and oxygen.
For this reaction, the free energy released is larger than the energy absorbed.

This ways combustion has an overall negative enthalpy and is an exothermic reaction.