Activity

Definition

Activity in chemistry refers to the effective concentration of a species in a solution. It accounts for interactions between molecules that alter their behavior compared to an ideal solution.

5 Must Know Facts For Your Next Test

1. Activity is used instead of concentration when dealing with non-ideal solutions.
2. The activity coefficient ($\gamma$) quantifies how much a substance's behavior deviates from ideality.
3. For dilute solutions, the activity is approximately equal to the molar concentration.
4. In concentrated solutions, interparticle forces cause significant deviations from ideality, affecting colligative properties.
5. Activity plays a crucial role in calculating accurate values for equilibrium constants and reaction rates.

Review Questions

• Why is activity used instead of concentration for non-ideal solutions?
• What does the activity coefficient represent?
• How does the activity affect calculations of colligative properties?

Related terms

Ideal Solution: A solution where the enthalpy of mixing is zero and components obey Raoult's Law across all compositions.

Colligative Properties:

Properties that depend on the number of solute particles in a solution, not their identity.

Molar Concentration: The number of moles of solute per liter of solution, often used as an approximation for activity in dilute solutions.