Question

What does it mean when $∆\mathrm{H}$ is negative?

Answer 1

1. In a thermodynamic system, Enthalpy is defined as the sum of internal energy and work done.
2. Here, work done is equal to the product of pressure and volume.
3. Change in enthalpy can mathematically be depicted as:$∆\mathrm{H}=∆\mathrm{U}+\mathrm{P}∆\mathrm{V}$
4. Where $∆\mathrm{H}$is a change in enthalpy, $∆\mathrm{U}$ is the change in internal energy, P is the pressure, $∆\mathrm{V}$ is the change in volume.
5. If the change in enthalpy is negative, the product formed is at a higher energy level as compared to reactants, this implies that net heat was absorbed, and the process is endothermic in nature.
6. If the change in enthalpy is positive, the product formed is at lower energy level as compared to reactants, this implies that net heat was evolved, and the process is exothermic in nature.