15 Questions
What is a characteristic of a reversible reaction?
It can take place in either direction
What occurs when the Kc value is high?
The forward reaction is predominant
What is the equilibrium constant of a reaction dependent on?
The concentration of the reactants and products at a given temperature
What is the state of dynamic balance in which the rate of the forward reaction equals the rate of the reverse reaction?
Chemical equilibrium
What is the name of the process used in the industrial manufacture of ammonia?
Haber process
What is the term for a reaction that goes to completion?
Irreversible reaction
What is the relationship between the rates of the forward and reverse reactions at chemical equilibrium?
The rates of the forward and reverse reactions are equal
What is a characteristic of the equilibrium constant (Kc)?
It is unaffected by changes in concentration of the reactants or products present in the reaction.
What is the purpose of calculating Kc values?
To determine the equilibrium concentrations of reactants and products.
What is the correct unit for the equilibrium constant (Kc)?
No units.
What is the purpose of finding the initial moles of reactants?
To determine the initial concentrations of reactants.
Why is it necessary to calculate the moles of reactants at equilibrium?
To calculate the equilibrium constant (Kc).
What is the correct way to calculate the equilibrium concentrations of reactants and products?
Using the initial moles of reactants and the stoichiometry of the reaction.
Why is it necessary to check the values of x obtained from a quadratic equation?
To reject values that are negative or too large.
What is the purpose of calculating the equilibrium concentrations of reactants and products?
To understand the behavior of a reaction at equilibrium.
Study Notes
Dynamic Equilibrium
- In a dynamic equilibrium, the concentration of reactants and products remains constant, but the forward and reverse reactions are still occurring.
- The rates of the forward and reverse reactions are equal at equilibrium.
Reversible Reactions
- Reversible reactions are reactions that can take place in either direction.
- Examples of reversible reactions include the formation of ammonia (N₂ + H₂ ⇌ NH₃) and the reaction between nitrogen and hydrogen.
Equilibrium Constant (Kc)
- The equilibrium constant (Kc) is a value that can be calculated by measuring the concentration of reactants and products at equilibrium.
- Kc is a constant value at a given temperature.
- The equilibrium constant expression is: Kc = [products] / [reactants]
- Kc values can be used to determine the direction of the reaction.
- When Kc is high, the forward reaction is predominant, and an abundance of product is produced.
- When Kc is low, the backward reaction is predominant, and not much product is produced.
Characteristics of Kc
- Kc is only relevant at equilibrium.
- Kc is altered only by a change in temperature.
- Kc is unaffected by changes in concentration of reactants or products.
- Kc may or may not have units.
Calculating Kc Values
- Examples of calculating Kc values include:
- Example 1: given the equilibrium concentrations, calculate the Kc value.
- Example 2: given the initial moles of reactants, calculate the Kc value.
- In some cases, a quadratic equation in x may result, and x is found using the quadratic formula.
Solving Equilibrium Problems
- To solve equilibrium problems, use the following steps:
- Write the equilibrium expression.
- Calculate the initial moles of reactants.
- Calculate the moles of reactants at equilibrium.
- Calculate the concentration of reactants at equilibrium.
- Substitute the values into the equilibrium expression to calculate Kc.
- Reject any negative values or values that are too large to be possible.
This quiz covers the concept of dynamic equilibrium, where the concentration of reactants and products remains constant, and reversible reactions, which can occur in both directions.
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