How does entropy relate to spontaneity in chemical reactions?

Here’s a explanation:

Entropy (S) and Spontaneity

• Entropy measures disorder or randomness in a system.
• In chemical reactions, spontaneous processes tend to increase the total entropy of the universe (system + surroundings).

Key Points:

1. Positive Entropy Change (ΔS > 0):
   • System becomes more disordered.
   • Reaction is more likely to be spontaneous.
2. Negative Entropy Change (ΔS < 0):
   • System becomes more ordered.
   • Reaction may still be spontaneous if heat is released (exothermic reaction).
3. Combined with Enthalpy (ΔH):
   • Spontaneity is predicted using Gibbs free energy:
     • Free energy decreases → reaction is spontaneous.
     • Free energy increases → reaction is non-spontaneous.

Simple Example:

• Ice melting at room temperature:
  • Disorder increases (ΔS > 0)
  • Heat is absorbed (ΔH > 0)
  • Overall, the process is spontaneous because the increase in entropy outweighs the energy absorbed.

In short: Higher entropy favors spontaneity, but the effect of enthalpy (heat released or absorbed) also matters.