Podcast
Questions and Answers
When is equilibrium reached?
When, in a closed system, the rates of the forward and reverse reactions are occurring in equal rates and there is no change in concentration of reactants and products.
What is the equilibrium constant? (Symbol)
Kc
What is the law of chemical equilibrium?
At a given temperature, the ratio of the concentration of products (raised to power of their molar coefficient) to the concentration of the reactants (raised to the power of their molar coefficients) is a constant.
What does the magnitude of the equilibrium constant indicate?
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What is the reaction quotient? (Symbol)
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What is the reaction quotient?
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What affects the position of equilibrium?
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Does a catalyst have an effect on the position of the equilibrium or equilibrium constant?
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What is dynamic equilibrium?
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Under what conditions will a saturated solution in a closed system establish a dynamic equilibrium?
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What happens at equilibrium?
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Does Kc have units?
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What does it mean if Kc is greater than 1?
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What does a large Kc mean?
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What does a small Kc indicate?
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What happens in a homogenous equilibrium?
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What happens in a heterogeneous equilibrium?
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What two points need to be considered when writing an equilibrium expression?
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How do you find Kc for the forward reaction?
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How do you find Kc for the reverse reaction?
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What happens to Kc when the reaction is reversed?
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What happens to Kc when the coefficients are halved?
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What happens to Kc when the coefficients are doubled?
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What happens to Kc when the change in reaction is the sum of equations?
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What happens to the equilibrium position and Kc when the concentration of products or reactants is changed?
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What happens to the equilibrium position and Kc when the pressure is changed?
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What happens to the equilibrium position and Kc when the temperature is changed?
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What happens to the equilibrium position and Kc when the catalyst is added?
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What is Le Chatelier's principle?
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Would a change in concentration affect Kc?
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When considering the effect of changes in pressure on a reaction, which state of the reactants do you refer to?
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If the pressure of the system is increased, which way will the equilibrium shift? (the reactants have more moles)
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If the pressure of the system is decreased, which way will the equilibrium shift? (the reactants have more moles)
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In an exothermic reaction, when the temperature is increased, how is the equilibrium position and equilibrium constant affected?
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In an exothermic reaction, when the temperature is decreased, how is the equilibrium position and equilibrium constant affected?
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In an endothermic reaction, when the temperature is increased, how is the equilibrium position and equilibrium constant affected?
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In an endothermic reaction, when the temperature is decreased, how is the equilibrium position and equilibrium constant affected?
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What does it mean if Q is greater than Kc?
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What does it mean if Q is less than Kc?
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What does it mean if Q = Kc?
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Study Notes
Equilibrium Basics
- Equilibrium is achieved in a closed system when the forward and reverse reaction rates are equal, resulting in stable reactant and product concentrations.
- Dynamic equilibrium means that while the sub-reactions continue, overall concentrations remain constant.
Equilibrium Constant and Reaction Quotient
- The equilibrium constant is symbolized as Kc, representing the ratio of product to reactant concentrations at equilibrium.
- The reaction quotient, denoted as Q, serves a similar purpose but is applicable at any point in the reaction, indicating whether the system is at equilibrium.
Factors Affecting Equilibrium
- Equilibrium position can shift due to changes in concentration, pressure, and temperature.
- A catalyst does not alter the position of equilibrium or the value of the equilibrium constant (Kc).
Laws and Principles of Chemical Equilibrium
- According to the law of chemical equilibrium, the ratio of concentrations of products to reactants remains constant at a given temperature.
- Le Chatelier's principle states that if a system at equilibrium experiences a change, the system will adjust to counteract that change, restoring balance.
Characteristics of Kc
- Kc is dimensionless; it has no units.
- A Kc greater than 1 indicates that products are favored, while a Kc less than 1 suggests reactants are favored.
- The magnitude of Kc reflects the proportion of products to reactants at equilibrium.
Influence of Temperature on Equilibrium
- In exothermic reactions, increasing temperature shifts the equilibrium to the left (favoring reactants), decreasing the Kc.
- In endothermic reactions, increasing temperature shifts the equilibrium to the right (favoring products), increasing the Kc.
Reaction Coefficients and Kc Changes
- Reversing a reaction inverses Kc (1/Kc).
- Halving coefficients results in the square root of Kc (√Kc).
- Doubling coefficients squares Kc (Kc²).
- Adding reactions multiplies Kc values (Kc = Kc1 x Kc2 x...).
Concentration and Pressure Effects
- Changes in concentration of reactants or products affect the equilibrium position but do not change Kc.
- Pressure changes influence equilibrium positions only when gaseous reactants are present; Kc remains unchanged.
Understanding Equilibrium Conditions
- A saturated solution establishes dynamic equilibrium when excess solid is present.
- In heterogeneous equilibria, reactants and products exist in multiple phases, while homogenous equilibria involve only one phase.
Q vs Kc Interpretations
- If Q > Kc, the reverse reaction is favored to reach equilibrium.
- If Q < Kc, the forward reaction is favored to reach equilibrium.
- Q = Kc indicates that the system is at equilibrium, with equal rates of forward and reverse reactions.
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Description
This quiz covers the fundamentals of chemical equilibrium, including equilibrium constants and reaction quotients. It discusses the factors that affect equilibrium positions and the principles governing dynamic equilibrium in closed systems. Test your understanding of these concepts and their applications.