Gen Chem II Free Energy and Equilibrium
35 flashcards covering Gen Chem II Free Energy and Equilibrium for the GENERAL-CHEMISTRY-2 Gen Chem II Topics section.
Free energy and equilibrium are fundamental concepts in General Chemistry II, focusing on the thermodynamic principles that govern chemical reactions and their spontaneity. The American Chemical Society (ACS) defines these topics within its curriculum guidelines, emphasizing the importance of understanding Gibbs free energy, reaction quotients, and equilibrium constants in predicting reaction behavior.
In practice exams and competency assessments, questions on free energy and equilibrium often require calculations involving Gibbs free energy changes, equilibrium concentrations, or shifts in equilibrium due to changes in conditions. A common pitfall is misinterpreting the relationship between free energy and equilibrium; many students mistakenly believe that a negative free energy change guarantees that a reaction will go to completion, overlooking the role of reaction kinetics.
A practical tip to remember is that while free energy indicates the direction of spontaneity, it does not provide information about the speed of the reaction, which is crucial in real-world applications.
Terms (35)
- 01
What is free energy?
Free energy is the energy in a system that can be used to do work at constant temperature and pressure, defined as G = H - TS, where G is Gibbs free energy, H is enthalpy, T is temperature, and S is entropy (Zumdahl, Thermodynamics chapter).
- 02
How is the change in Gibbs free energy (ΔG) calculated?
ΔG is calculated using the equation ΔG = ΔH - TΔS, where ΔH is the change in enthalpy, T is the temperature in Kelvin, and ΔS is the change in entropy (Zumdahl, Thermodynamics chapter).
- 03
What does a negative ΔG indicate about a reaction?
A negative ΔG indicates that a reaction is spontaneous under standard conditions, meaning it can proceed without external energy input (Brown LeMay, Thermodynamics chapter).
- 04
What is the relationship between ΔG and the equilibrium constant (K)?
The relationship is given by the equation ΔG° = -RT ln(K), where R is the universal gas constant and T is the temperature in Kelvin. A positive K indicates a spontaneous reaction (Brown LeMay, Thermodynamics chapter).
- 05
How does temperature affect the spontaneity of a reaction?
Temperature can affect spontaneity through the term -TΔS in the Gibbs free energy equation; an increase in temperature can make a reaction spontaneous if ΔS is positive (Zumdahl, Thermodynamics chapter).
- 06
What is the standard free energy change (ΔG°)?
ΔG° is the change in Gibbs free energy under standard conditions, typically defined as 1 atm pressure and 25°C (298 K) for all reactants and products in their standard states (Brown LeMay, Thermodynamics chapter).
- 07
When is a reaction at equilibrium?
A reaction is at equilibrium when the rate of the forward reaction equals the rate of the reverse reaction, resulting in constant concentrations of reactants and products (Tro, Chemical Equilibrium chapter).
- 08
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 position of equilibrium (Brown LeMay, Chemical Equilibrium chapter).
- 09
What does it mean if K > 1?
If K > 1, it indicates that at equilibrium, the concentration of products is greater than that of reactants, favoring the formation of products (Tro, Chemical Equilibrium chapter).
- 10
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 (Zumdahl, Chemical Equilibrium chapter).
- 11
How does increasing pressure affect a gaseous equilibrium?
Increasing pressure shifts the equilibrium position towards the side with fewer moles of gas, according to Le Chatelier's principle (Tro, Chemical Equilibrium chapter).
- 12
What is the effect of temperature on an exothermic reaction at equilibrium?
For an exothermic reaction, increasing temperature shifts the equilibrium position to favor the reactants, while decreasing temperature favors the products (Brown LeMay, Chemical Equilibrium chapter).
- 13
What is the formula for calculating the reaction quotient (Q)?
The reaction quotient (Q) is calculated using the same expression as the equilibrium constant (K), but with the current concentrations of reactants and products (Tro, Chemical Equilibrium chapter).
- 14
When is Q equal to K?
Q is equal to K when a reaction is at equilibrium, meaning the concentrations of reactants and products remain constant (Brown LeMay, Chemical Equilibrium chapter).
- 15
What happens to Q when a reactant is added to a system at equilibrium?
When a reactant is added, Q decreases, causing the system to shift towards the products to re-establish equilibrium (Zumdahl, Chemical Equilibrium chapter).
- 16
How can catalysts affect equilibrium?
Catalysts speed up the rate of both the forward and reverse reactions equally, allowing equilibrium to be reached faster, but they do not change the position of equilibrium (Tro, Chemical Equilibrium chapter).
- 17
What is the significance of ΔG° in predicting reaction spontaneity?
ΔG° provides a criterion for spontaneity under standard conditions; a negative ΔG° indicates a spontaneous reaction, while a positive ΔG° indicates non-spontaneity (Brown LeMay, Thermodynamics chapter).
- 18
What is the relationship between ΔG and reaction direction?
If ΔG is negative, the reaction proceeds in the forward direction; if ΔG is positive, the reaction favors the reverse direction (Zumdahl, Thermodynamics chapter).
- 19
What does it mean if K < 1?
If K < 1, it indicates that at equilibrium, the concentration of reactants is greater than that of products, favoring the formation of reactants (Tro, Chemical Equilibrium chapter).
- 20
How does the addition of an inert gas affect a gaseous equilibrium?
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 (Brown LeMay, Chemical Equilibrium chapter).
- 21
What is the effect of decreasing volume on a gaseous reaction at equilibrium?
Decreasing volume increases pressure, which shifts the equilibrium towards the side with fewer moles of gas (Tro, Chemical Equilibrium chapter).
- 22
How does ΔH relate to reaction spontaneity?
ΔH influences spontaneity; exothermic reactions (negative ΔH) are generally more likely to be spontaneous than endothermic reactions (positive ΔH) (Brown LeMay, Thermodynamics chapter).
- 23
What is the significance of entropy (S) in thermodynamics?
Entropy (S) measures the disorder or randomness of a system; higher entropy indicates greater disorder and is a key factor in determining spontaneity (Zumdahl, Thermodynamics chapter).
- 24
What is the effect of temperature on the equilibrium constant (K)?
The equilibrium constant (K) is temperature-dependent; changes in temperature can alter K, affecting the position of equilibrium (Tro, Chemical Equilibrium chapter).
- 25
What is the difference between ΔH and ΔG?
ΔH is the change in enthalpy, a measure of heat content, while ΔG is the change in Gibbs free energy, which determines spontaneity (Brown LeMay, Thermodynamics chapter).
- 26
What is the role of free energy in biochemical reactions?
Free energy changes in biochemical reactions determine the direction and feasibility of metabolic processes (Tro, Biochemistry chapter).
- 27
What is the significance of standard conditions in thermodynamics?
Standard conditions (1 atm, 298 K) provide a reference point for comparing thermodynamic data, including ΔG° and K (Brown LeMay, Thermodynamics chapter).
- 28
How does ΔS influence the spontaneity of a reaction?
A positive ΔS indicates an increase in disorder, which favors spontaneity; a negative ΔS can hinder spontaneity unless compensated by a sufficiently negative ΔH (Zumdahl, Thermodynamics chapter).
- 29
What is the effect of a catalyst on the activation energy of a reaction?
A catalyst lowers the activation energy of a reaction, allowing it to proceed faster without altering the equilibrium position (Tro, Kinetics chapter).
- 30
What is the principle behind the common ion effect?
The common ion effect states that the solubility of a salt decreases in a solution that already contains one of its ions, affecting equilibrium (Brown LeMay, Solubility chapter).
- 31
What is the relationship between Gibbs free energy and work?
Gibbs free energy represents the maximum reversible work that can be performed by a thermodynamic system at constant temperature and pressure (Zumdahl, Thermodynamics chapter).
- 32
What is the effect of dilution on a system at equilibrium?
Diluting a system at equilibrium decreases the concentrations of all species, potentially shifting the equilibrium position depending on the stoichiometry (Tro, Chemical Equilibrium chapter).
- 33
How does ΔG change with reaction progress?
ΔG changes as a reaction progresses towards equilibrium; it decreases for spontaneous reactions until it reaches zero at equilibrium (Brown LeMay, Thermodynamics chapter).
- 34
What is the significance of phase changes in relation to equilibrium?
Phase changes, such as melting or boiling, involve equilibria between phases, where the rates of phase transitions are equal (Tro, Phase Equilibrium chapter).
- 35
What is the effect of temperature on solubility at equilibrium?
For many solids, increasing temperature increases solubility, while for gases, higher temperatures generally decrease solubility (Brown LeMay, Solubility chapter).