EQUILÍBRIO QUÍMICO: DEFINIÇÃO, CÁLCULOS E GRÁFICOS | Resumo de Química para o Enem

Summary

In this video, the concept of chemical equilibrium is explained, focusing on reversible reactions. It covers the dynamic balance between reactants and products, emphasizing how equilibrium is reached when the rates of the forward and reverse reactions are equal. The video introduces key concepts such as reaction rates, equilibrium constants, and the factors influencing equilibrium, like concentration and pressure. Practical examples, including reactions with gases and the exclusion of solids and water in equilibrium calculations, are also discussed, making the topic accessible to viewers interested in understanding chemical processes.

Takeaways

• 😀 Chemical equilibrium occurs when the rate of the forward reaction equals the rate of the reverse reaction.
• 😀 Reversible reactions are key to understanding chemical equilibrium, where reactants transform into products, and products also transform back into reactants.
• 😀 In a reversible reaction, the concentrations of reactants and products become constant when equilibrium is reached.
• 😀 At equilibrium, the forward and reverse reaction rates are equal, even though both reactions continue to occur.
• 😀 The equilibrium constant expression (K) is derived from the concentrations of products over reactants, each raised to the power of their stoichiometric coefficients.
• 😀 Water and solids are not included in the equilibrium constant expression because water is present in large quantities and solids do not have a well-defined concentration.
• 😀 The equilibrium constant is represented by the ratio of product concentrations to reactant concentrations at equilibrium.
• 😀 Le Chatelier's Principle suggests that if a system at equilibrium is disturbed, the system will adjust to counteract the disturbance and restore equilibrium.
• 😀 In some chemical equilibria, pressure is a key factor, such as in gas reactions, where the equilibrium constant involves partial pressures of gases.
• 😀 Reactions in aqueous solutions may have different equilibrium constants depending on whether they involve gases or liquids, like the reaction of CO2 in water forming carbonic acid.

Q & A

What is chemical equilibrium?

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

How is a reversible reaction represented?

A reversible reaction is represented with a reaction arrow that points both ways (↔), indicating that reactants convert into products and, at the same time, products convert back into reactants.

What does the rate of a chemical reaction depend on?

The rate of a chemical reaction depends on the concentration of the reactants and products. As the reaction proceeds, the concentration of reactants decreases while the concentration of products increases, leading to a change in reaction rates.

When does chemical equilibrium occur?

Chemical equilibrium occurs when the rates of the forward and reverse reactions are equal, meaning that the concentrations of reactants and products do not change over time.

What does the equilibrium constant (K) represent in a chemical reaction?

The equilibrium constant (K) represents the ratio of the concentrations of products to reactants, each raised to the power of their respective coefficients, at equilibrium. It is constant for a given reaction at a specific temperature.

Why do water and solids not appear in the equilibrium expression?

Water and solids do not appear in the equilibrium expression because water is usually present in excess and its concentration remains effectively constant, and solids do not have a known concentration in equilibrium as they are not dissolved in the solution.

What is the difference between equilibrium expressions for concentration and pressure?

When dealing with gases, equilibrium expressions are written in terms of pressure (not concentration). The equilibrium constant is then based on the partial pressures of the gases involved in the reaction.

How does the reaction shift when there is an increase in pressure in a system involving gases?

In a system involving gases, an increase in pressure generally shifts the equilibrium toward the side with fewer gas molecules to reduce the pressure, as per Le Chatelier's Principle.

What role does temperature play in chemical equilibrium?

Temperature can affect the position of equilibrium. For an exothermic reaction, increasing temperature shifts the equilibrium to favor the reactants, while for an endothermic reaction, increasing temperature shifts the equilibrium to favor the products.

What is an example of a chemical reaction that involves equilibrium and pressure?

An example of a chemical reaction involving equilibrium and pressure is the formation of carbonic acid (H2CO3) from CO2 and H2O in aqueous solution. The equilibrium is governed by the pressure of CO2 in the system.