# Are single displacement reactions exothermic?

Mar 21, 2016

Are single displacement reactions exothermic

Yes, single displacement reactions are exothermic.

Definition

The general formula for a single replacement reaction is

$\text{A + B-C → B + A-C}$

where $\text{A}$ is an element and where $\text{B-C}$ is a compound.

The reaction produces a new element $\text{B}$ and a new compound $\text{A-C}$.

Energy changes

When a chemical reaction takes place, energy is either released or absorbed.

If energy is released, the reaction is exothermic.

Bond formation is an exothermic process.

Energy is released because the atoms are going to a lower energy state.

By the same argument, it takes energy to break a bond (endothermic).

Conclusion

In the reaction $\text{A + B-C → B + A-C}$, we must break the $\text{B-C}$ bond and form an $\text{A-C}$ bond.

If formation of the $\text{A-C}$ bond releases more energy than it took to break the $\text{B-C}$ bond, there will be a net release of energy.

The reaction will be exothermic.

It the process is endothermic, the reaction will not occur spontaneously, because the system is already in its more stable state.

Hence, single displacement reactions are exothermic.