AP Chem Free Energy and Equilibrium
34 flashcards covering AP Chem Free Energy and Equilibrium for the AP-CHEMISTRY Unit 9 section.
Free energy and equilibrium are fundamental concepts in AP Chemistry, specifically outlined in the College Board's AP Chemistry Curriculum Framework. This topic encompasses the relationship between thermodynamics and chemical reactions, focusing on Gibbs free energy, reaction spontaneity, and equilibrium constants. Understanding these principles allows students to predict how changes in conditions affect chemical systems.
In practice exams and competency assessments, questions often involve calculations related to free energy changes and equilibrium shifts, frequently using scenarios that require students to apply Le Chatelier's principle. A common pitfall is misinterpreting the direction of equilibrium shifts when external conditions change, leading to incorrect conclusions about reaction behavior. Students may also struggle with the mathematical aspects, particularly in calculating Gibbs free energy from standard conditions.
A practical tip to remember is that small changes in temperature or concentration can significantly impact equilibrium positions, so always consider these factors when analyzing a reaction.
Terms (34)
- 01
What is the definition of Gibbs free energy?
Gibbs free energy (G) is a thermodynamic potential that measures the maximum reversible work obtainable from a closed system at constant temperature and pressure. It is defined as G = H - TS, where H is enthalpy, T is temperature, and S is entropy (College Board AP Course and Exam Description).
- 02
How does temperature affect the equilibrium constant?
The equilibrium constant (K) is temperature-dependent; as temperature increases, K may increase or decrease depending on whether the reaction is exothermic or endothermic, as described by the van 't Hoff equation (College Board released AP practice exam questions).
- 03
What is the relationship between ΔG and equilibrium?
At equilibrium, the change in Gibbs free energy (ΔG) is zero, indicating that the forward and reverse reactions occur at the same rate (College Board AP Course and Exam Description).
- 04
Define the standard free energy change (ΔG°).
The standard free energy change (ΔG°) is the change in Gibbs free energy under standard conditions (1 bar pressure, 1 M concentration) for reactants and products (College Board AP Course and Exam Description).
- 05
When is a reaction spontaneous based on ΔG?
A reaction is spontaneous when the change in Gibbs free energy (ΔG) is negative, indicating that the reaction can proceed without external energy input (College Board AP Course and Exam Description).
- 06
What is the effect of increasing concentration on equilibrium position?
Increasing the concentration of reactants shifts the equilibrium position to the right, favoring the formation of products, according to Le Chatelier's principle (College Board released AP practice exam questions).
- 07
How often must laboratory equipment be calibrated for accurate measurements?
Laboratory equipment should be calibrated regularly, typically before each use or at least annually, to ensure accurate measurements (College Board AP Course and Exam Description).
- 08
What is Le Chatelier's principle?
Le Chatelier's principle states that if a dynamic equilibrium is disturbed by changing the conditions, the position of equilibrium shifts to counteract the change (College Board released AP practice exam questions).
- 09
What does a negative ΔG° indicate about a reaction?
A negative ΔG° indicates that the reaction is thermodynamically favorable and can occur spontaneously under standard conditions (College Board AP Course and Exam Description).
- 10
What is the significance of the equilibrium constant (K)?
The equilibrium constant (K) quantifies the ratio of the concentrations of products to reactants at equilibrium, providing insight into the extent of a reaction (College Board AP Course and Exam Description).
- 11
How does pressure affect gaseous equilibria?
Increasing pressure shifts the equilibrium position toward the side with fewer moles of gas, according to Le Chatelier's principle (College Board released AP practice exam questions).
- 12
What is the formula for calculating Gibbs free energy change?
The Gibbs free energy change (ΔG) can be calculated using the formula ΔG = ΔH - TΔS, where ΔH is the change in enthalpy, T is the temperature in Kelvin, and ΔS is the change in entropy (College Board AP Course and Exam Description).
- 13
What is the effect of temperature on the equilibrium constant for an exothermic reaction?
For an exothermic reaction, increasing the temperature decreases the equilibrium constant (K), as the system shifts to favor reactants (College Board AP Course and Exam Description).
- 14
What is the relationship between ΔG and the equilibrium constant K?
The relationship between ΔG and the equilibrium constant (K) is given by the equation ΔG° = -RT ln(K), where R is the gas constant and T is temperature in Kelvin (College Board AP Course and Exam Description).
- 15
Define entropy (S) in a thermodynamic context.
Entropy (S) is a measure of the disorder or randomness of a system, reflecting the number of possible microstates corresponding to a thermodynamic state (College Board AP Course and Exam Description).
- 16
What happens to the equilibrium position if a reactant is removed?
Removing a reactant shifts the equilibrium position to the left, favoring the formation of reactants, according to Le Chatelier's principle (College Board released AP practice exam questions).
- 17
How does the addition of an inert gas affect the equilibrium of a reaction?
Adding an inert gas at constant volume does not affect the equilibrium position, as it does not change the partial pressures of the reactants or products (College Board released AP practice exam questions).
- 18
What is the standard state for a substance?
The standard state for a substance is its pure form at 1 bar pressure and a specified temperature, usually 25 °C (298 K) (College Board AP Course and Exam Description).
- 19
What is the effect of decreasing volume on gaseous equilibria?
Decreasing the volume of a system at equilibrium increases the pressure, shifting the equilibrium position toward the side with fewer moles of gas (College Board released AP practice exam questions).
- 20
What is the formula for calculating the change in Gibbs free energy at non-standard conditions?
The change in Gibbs free energy at non-standard conditions can be calculated using ΔG = ΔG° + RT ln(Q), where Q is the reaction quotient (College Board AP Course and Exam Description).
- 21
How does an increase in temperature affect an endothermic reaction at equilibrium?
Increasing the temperature of an endothermic reaction shifts the equilibrium position to the right, favoring the formation of products (College Board released AP practice exam questions).
- 22
What is the significance of ΔS in thermodynamics?
ΔS, or the change in entropy, indicates the degree of disorder in a system; a positive ΔS suggests increased disorder (College Board AP Course and Exam Description).
- 23
What is the relationship between free energy and work?
The change in Gibbs free energy (ΔG) represents the maximum reversible work that can be performed by a system at constant temperature and pressure (College Board AP Course and Exam Description).
- 24
Define the reaction quotient (Q).
The reaction quotient (Q) is the ratio of the concentrations of products to reactants at any point in a reaction, used to determine the direction of the reaction (College Board AP Course and Exam Description).
- 25
What occurs when a system at equilibrium is disturbed?
When a system at equilibrium is disturbed, it will shift in a direction that counteracts the disturbance, as described by Le Chatelier's principle (College Board released AP practice exam questions).
- 26
What is the effect of catalyst on equilibrium position?
A catalyst does not affect the position of equilibrium; it only speeds up the rate at which equilibrium is reached (College Board released AP practice exam questions).
- 27
How is the standard free energy change related to the equilibrium constant?
The standard free energy change (ΔG°) is related to the equilibrium constant (K) through the equation ΔG° = -RT ln(K), indicating how favorability relates to equilibrium (College Board AP Course and Exam Description).
- 28
What is the impact of increasing temperature on an exothermic reaction?
Increasing the temperature of an exothermic reaction shifts the equilibrium position to the left, favoring the reactants (College Board released AP practice exam questions).
- 29
What does it mean if ΔG is positive?
If ΔG is positive, the reaction is non-spontaneous under the given conditions, indicating that it requires energy input to proceed (College Board AP Course and Exam Description).
- 30
How does the addition of a product affect equilibrium?
Adding a product shifts the equilibrium position to the left, favoring the formation of reactants, according to Le Chatelier's principle (College Board released AP practice exam questions).
- 31
What is the significance of the equilibrium constant (K) being greater than 1?
An equilibrium constant (K) greater than 1 indicates that at equilibrium, the concentration of products is greater than that of reactants, suggesting a product-favored reaction (College Board AP Course and Exam Description).
- 32
What is the effect of dilution on equilibrium?
Diluting a reaction mixture generally shifts the equilibrium position toward the side with more moles of solute, according to Le Chatelier's principle (College Board released AP practice exam questions).
- 33
What is the relationship between ΔH and reaction spontaneity?
A reaction is more likely to be spontaneous if it has a negative ΔH (exothermic) and a positive ΔS (increase in entropy), but the overall spontaneity is determined by ΔG (College Board AP Course and Exam Description).
- 34
Define the term 'spontaneous process' in thermodynamics.
A spontaneous process is one that occurs without external intervention, typically characterized by a decrease in free energy (ΔG < 0) (College Board AP Course and Exam Description).