Which concept is described by the first law of thermodynamics?

• A. Increase in entropy
• B. Conservation of energy
• C. Spontaneity of chemical reactions
• D. Equilibrium constant

Answer: (B)

Verified step by step guidance

1. Understand that the first law of thermodynamics is a fundamental principle in chemistry and physics that deals with energy changes in a system.
2. Recall that the first law states that energy cannot be created or destroyed, only transformed from one form to another or transferred between a system and its surroundings.
3. Recognize that this principle is often expressed mathematically as \(\Delta U = q + w\), where \(\Delta U\) is the change in internal energy of the system, \(q\) is the heat added to the system, and \(w\) is the work done on the system.
4. Note that this law implies the conservation of energy, meaning the total energy of an isolated system remains constant.
5. Conclude that among the given options, the concept described by the first law of thermodynamics is the conservation of energy.