1. Equilíbrio Químico: Conceito e Características (1/2) [Físico Química]

Summary

This video introduces the concept of chemical equilibrium, explaining how some reactions are reversible, meaning the products can convert back into reactants. It emphasizes that equilibrium is not a static or equal state but one where the concentrations of reactants and products remain constant over time due to equal rates of forward and reverse reactions. While the system may seem stable macroscopically, it remains dynamic at the microscopic level. The importance of closed systems for equilibrium is also highlighted, ensuring that nothing escapes, allowing the reaction to reach a balanced state.

Takeaways

• 😀 Chemical equilibrium refers to reactions that do not always complete or reach 100% yield, unlike irreversible reactions.
• 😀 In a reversible reaction, products can decompose and turn back into reactants, creating a dynamic process.
• 😀 A reaction is at equilibrium when the concentrations of reactants and products remain constant over time.
• 😀 The concept of equilibrium is dynamic, meaning reactions continue at the molecular level even if the overall concentration appears constant.
• 😀 Reactions can reach equilibrium where the rate of the forward reaction equals the rate of the reverse reaction.
• 😀 At equilibrium, the concentrations of reactants and products become constant, but the reactions are still occurring at equal rates.
• 😀 Chemical equilibrium is achieved when the forward and reverse reaction speeds are balanced.
• 😀 In a system at equilibrium, the macroscopic appearance does not change, as concentrations remain steady.
• 😀 A system needs to be closed to maintain equilibrium, especially for reactions involving gases, which could escape in an open system.
• 😀 The equilibrium constant (K) helps to determine the balance between reactants and products in a system.
• 😀 Chemical equilibrium is essential in understanding how reactions proceed and maintain a stable state without observable change.

Q & A

What is chemical equilibrium?

Chemical equilibrium refers to the state in a reversible reaction where the concentrations of reactants and products remain constant over time because the rates of the forward and reverse reactions are equal.

What happens during a reversible reaction?

In a reversible reaction, the products can react to form the original reactants again. This leads to both forward and reverse reactions occurring simultaneously.

How does a reaction reach equilibrium?

A reaction reaches equilibrium when the concentrations of the reactants and products become constant because the rate of the forward reaction equals the rate of the reverse reaction.

What is the difference between macroscopic and microscopic views in equilibrium?

In the macroscopic view, there is no visible change in the system, such as no change in color or concentration. In the microscopic view, molecular-level interactions continue to occur even though there is no observable change.

Can the concentrations of reactants and products vary at equilibrium?

No, at equilibrium, the concentrations of reactants and products become constant. The system has reached a dynamic balance where the rates of the forward and reverse reactions are equal.

Why is a closed system necessary for equilibrium?

A closed system is necessary to ensure that no reactants or products escape the reaction environment. If a product, especially a gas, were to escape, equilibrium could not be maintained, and the reaction could not proceed to completion.

What happens at the molecular level in an equilibrium reaction?

At the molecular level, even though the concentrations of reactants and products remain constant at equilibrium, molecules continue to collide, react, and form new molecules, but the rate of these reactions is equal in both directions.

How do the forward and reverse reaction rates compare at equilibrium?

At equilibrium, the rate of the forward reaction is equal to the rate of the reverse reaction, meaning that the amount of reactants being converted into products is balanced by the amount of products being converted back into reactants.

What does it mean for a reaction to be dynamic at equilibrium?

A reaction is dynamic at equilibrium because the molecular interactions never stop. The system is in a state of balance, with constant microscopic activity, but no macroscopic changes are observed.

What is an example of a non-reversible reaction mentioned in the script?

An example of a non-reversible reaction given in the script is the burning of a piece of paper. Once the paper is burned, it cannot return to its original form, making the reaction irreversible.