Questions and Answers
What is the characteristic of a system in chemical equilibrium?
What happens to the concentrations of reactants and products in a system at chemical equilibrium?
What is the condition for a system to reach chemical equilibrium?
What is the characteristic of a reaction that does not go to completion?
Signup and view all the answers
What is the direction of the reverse reaction in a system at chemical equilibrium?
Signup and view all the answers
What is the consequence of a system reaching chemical equilibrium?
Signup and view all the answers
What is the primary goal of Le Chatelier's Principle?
Signup and view all the answers
What is the relationship between ∆G and K at equilibrium?
Signup and view all the answers
What is the role of the reaction quotient (Q) in the equation ∆G = ∆G° + RT ln Q?
Signup and view all the answers
What is the unit of the ideal gas constant (R)?
Signup and view all the answers
What is the primary focus of chemical kinetics?
Signup and view all the answers
What is the result of applying a stress to a system at equilibrium?
Signup and view all the answers
What is the law of mass action?
Signup and view all the answers
What is the equilibrium constant in terms of concentration?
Signup and view all the answers
What happens to the equilibrium constant (K) if the concentration of reactants increases?
Signup and view all the answers
What is the effect of increasing the pressure on the equilibrium constant (K) for a reaction involving gases?
Signup and view all the answers
What happens to the equilibrium constant (K) if the temperature increases for an endothermic reaction?
Signup and view all the answers
What is the equilibrium constant in terms of partial pressures?
Signup and view all the answers
What happens to the equilibrium constant (K) if a catalyst is added to the reaction?
Signup and view all the answers
What is the effect of decreasing the concentration of products on the equilibrium constant (K)?
Signup and view all the answers
What is the equilibrium constant (K) for a reaction in which all reactants and products are gases?
Signup and view all the answers
What is the effect of increasing the temperature on the equilibrium constant (K) for an exothermic reaction?
Signup and view all the answers
Study Notes
Gibbs Free Energy
- Gibbs free energy (∆G) can be expressed in several different equations:
- ∆G° = ∑ G° (products) - ∑ G° (reactants)
- ∆G° = -nFE°
- ∆G = ∆G° + RT lnQ
- ∆G° is the standard Gibbs free energy, and K is the equilibrium constant
- At equilibrium, ∆G = 0, and Q = K
Chemical Equilibrium
- Chemical equilibrium is a state where the rate of the forward reaction equals the rate of the backward reaction
- It is the state where the concentrations of all reactants and products remain constant with time at any given temperature
- Any chemical reaction carried out in a closed vessel will reach equilibrium
- Many reactions do not go to completion, and the products react to form the original reactants once more
Le Chatelier's Principle
- This principle states that if a stress is applied on a system at equilibrium, the equilibrium will tend to shift in a direction to relieve that stress
- Examples of stresses include changes in concentration, pressure, and temperature
- A shift is a net reaction of reactants to form products or of products to form reactants
Chemical Kinetics
- Chemical kinetics is the area of chemistry that deals with the study of the rate (speed) and mechanism of reactions
- One of the main goals of chemical kinetics is to understand the steps by which a reaction takes place
Law of Mass Action
- The law of mass action states that the rate of a chemical reaction is proportional to the product of the molar concentrations of the reacting substances
- For the general reaction: A + B ⇌ C + D, the rate of forward reaction (RF) is proportional to [A][B], and the rate of reverse reaction (RR) is proportional to [C][D]
- RF = kF[A][B] and RR = kR[C][D], where kF and kR are constants of proportionality or rate constants
Equilibrium Constant
- The equilibrium constant (Kc) is a ratio of the product of the molar concentrations of the products to the product of the molar concentrations of the reactants
- Kc = [C]r [D]s / [A]p [B]q, where p, q, r, and s are the numbers of moles of A, B, C, and D respectively
- The equilibrium constant indicates the position of equilibrium, such that:
- If K > 1, the equilibrium lies to the right, and products predominate
- If K < 1, the equilibrium lies to the left, and reactants predominate
- If K = 1, the equilibrium mixture contains equal amounts of products and reactants
Equilibrium Expression for Gases
- For gases, the equilibrium constant may be more usefully interpreted in terms of their partial pressures
- Kp = 𝑝C 𝑝D / 𝑝A 𝑝B, where Kp is the equilibrium constant in terms of partial pressure
Factors that Affect the Equilibrium Constant
- Composition of equilibrium mixture:
- Concentration of reactant increased: shift to right, no effect on K
- Concentration of reactant decreased: shift to left, no effect on K
- Pressure:
- Increased or decreased: no effect on K, unless reaction involves a volume change
- Temperature:
- Increased or decreased: change in K depends on the sign of ∆H
- Addition of catalyst: no effect on K
- Solving equilibrium problems:
- Write the balanced equation for the reaction
- Write the equilibrium expression using the law of mass action
- List the initial concentrations
- Apply the changes to the initial concentrations
- Substitute the equilibrium concentrations into the equilibrium expression
- Solve for the unknown
Studying That Suits You
Use AI to generate personalized quizzes and flashcards to suit your learning preferences.
Description
Practice problems determining reaction feasibility using Gibbs free energy equations, including calculating ΔG values and evaluating reaction spontaneity.
