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### Course: AP®︎/College Chemistry>Unit 7

Lesson 1: Introduction to equilibrium

# Dynamic equilibrium

Many physical and chemical processes are reversible. A reversible process is said to be in dynamic equilibrium when the forward and reverse processes occur at the same rate, resulting in no observable change in the system. Once dynamic equilibrium is established, the concentrations or partial pressures of all species involved in the process remain constant. Created by Jay.

## Want to join the conversation?

• Why would the reaction be at equilibrium in 0.2M and 0.6M? Shouldn't it be at equilibrium in 0.25M and 0.5M, because we need the number of moles of X2 be twice the number of 2X?
• Equilibrium means that the forward and reverse reaction rates are equal, not that the product and reactant concentrations be equal. We can have wildly different concentrations for both and a reaction can be at equilibrium. At equilibrium the reaction reaches a point where the concentrations of the chemicals do not appreciably change anymore because products are being formed at the same rate reactants are.

Hope that helps.
• Are X_2 and X actual gases? If so, which gases are they?
(1 vote)
• So those aren't any specific gases. Using X2 and X is just a general way to write the equation which could use any elements we wanted. Think of X being used here as a variable in the same way that it's used in algebra.

Hope that helps.
• How does this work considering thermodynamics? Is the entrophy highest at t0 or at t20?