Chemical thermodynamics

Definition

Chemical thermodynamics studies the interrelation of heat and work with chemical reactions or physical changes. It applies principles of thermodynamics to predict the direction and extent of chemical processes.

5 Must Know Facts For Your Next Test

1. The first law of thermodynamics states that energy cannot be created or destroyed, only transformed.
2. Enthalpy ($H$) is a state function used to describe the heat content of a system at constant pressure.
3. Endothermic reactions absorb heat, resulting in a positive change in enthalpy ($\Delta H > 0$).
4. Exothermic reactions release heat, resulting in a negative change in enthalpy ($\Delta H < 0$).
5. Hess's Law states that the total enthalpy change for a reaction is the sum of all changes, regardless of the pathway taken.

Review Questions

• What is the significance of enthalpy ($H$) in chemical thermodynamics?
• How does the first law of thermodynamics apply to chemical reactions?
• Explain Hess's Law and its application to determining reaction enthalpies.

Related terms

Enthalpy: A measure of the total energy content in a system, including internal energy and pressure-volume work.

Entropy: A measure of disorder or randomness in a system; it helps predict spontaneous processes.

Gibbs Free Energy: $G = H - TS$, where $G$ indicates spontaneity; if $\Delta G < 0$, the process is spontaneous under constant temperature and pressure.