AP Chem Equilibrium Constant K
35 flashcards covering AP Chem Equilibrium Constant K for the AP-CHEMISTRY Unit 7 section.
The equilibrium constant, K, is a fundamental concept in AP Chemistry that measures the ratio of the concentration of products to reactants at equilibrium for a given chemical reaction. Defined by the College Board in the AP Chemistry Curriculum Framework, this topic is essential for understanding dynamic chemical systems and their behaviors.
In practice exams and competency assessments, questions about K often require students to calculate the equilibrium constant from given concentrations or to interpret changes in K with variations in temperature. A common pitfall is neglecting to consider the stoichiometry of the balanced equation when determining the exponent values for each concentration in the K expression. Misapplying these principles can lead to significant errors in calculations.
A practical tip to remember is that changes in temperature can affect the value of K, so always pay attention to the conditions under which the equilibrium is established.
Terms (35)
- 01
What is the equilibrium constant expression for the reaction aA + bB ⇌ cC + dD?
The equilibrium constant expression is K = [C]^c [D]^d / [A]^a [B]^b, where the brackets denote the molar concentrations of the reactants and products at equilibrium (College Board CED).
- 02
How does temperature affect the equilibrium constant K?
The value of the equilibrium constant K changes with temperature; it increases for endothermic reactions and decreases for exothermic reactions (College Board CED).
- 03
What happens to K when a reaction is reversed?
When a reaction is reversed, the new equilibrium constant K' is the reciprocal of the original K; K' = 1/K (College Board CED).
- 04
Define the term 'dynamic equilibrium' in the context of chemical reactions.
Dynamic equilibrium refers to the state in which the rates of the forward and reverse reactions are equal, resulting in constant concentrations of reactants and products (College Board CED).
- 05
What is the relationship between K and the reaction quotient Q?
If Q < K, the reaction will proceed to the right to form more products; if Q > K, the reaction will proceed to the left to form more reactants (College Board CED).
- 06
How do changes in concentration affect the equilibrium position?
Increasing the concentration of reactants shifts the equilibrium to the right, while increasing the concentration of products shifts it to the left (College Board CED).
- 07
What is the effect of adding an inert gas to a system at equilibrium?
Adding an inert gas at constant volume does not affect the equilibrium position or the value of K, as it does not change the partial pressures of the reactants or products (College Board CED).
- 08
What is the significance of a large K value?
A large K value (K >> 1) indicates that at equilibrium, the concentration of products is much greater than that of reactants, favoring product formation (College Board CED).
- 09
What does a K value of less than 1 indicate about a reaction?
A K value less than 1 (K << 1) indicates that at equilibrium, the concentration of reactants is greater than that of products, favoring reactant formation (College Board CED).
- 10
How is K affected by the stoichiometry of a balanced equation?
If the coefficients in a balanced equation are multiplied by a factor, the equilibrium constant K is raised to the power of that factor (College Board CED).
- 11
What is the equilibrium constant expression for the dissociation of water?
For the reaction 2H2O ⇌ H2 + O2, the equilibrium constant expression is K = [H2][O2] / [H2O]^2 (College Board CED).
- 12
What is the relationship between Kp and Kc for a gas-phase reaction?
Kp = Kc(RT)^(Δn), where Δn is the change in moles of gas, R is the gas constant, and T is the temperature in Kelvin (College Board CED).
- 13
When does K remain constant despite changes in pressure?
K remains constant when only the volume or pressure of the system is changed, as long as the temperature is constant (College Board CED).
- 14
What does it mean if K is equal to 1?
If K equals 1, it indicates that at equilibrium, the concentrations of reactants and products are approximately equal (College Board CED).
- 15
What is the effect of temperature on the equilibrium constant for an exothermic reaction?
For an exothermic reaction, increasing the temperature decreases the value of the equilibrium constant K (College Board CED).
- 16
What is the principle behind Le Chatelier's principle?
Le Chatelier's principle states that if a system at equilibrium is disturbed, it will shift in a direction that counteracts the disturbance (College Board CED).
- 17
How does the addition of a catalyst affect the equilibrium constant?
The addition of a catalyst does not change the value of the equilibrium constant; it only speeds up the rate at which equilibrium is reached (College Board CED).
- 18
What is the equilibrium constant for the reaction N2(g) + 3H2(g) ⇌ 2NH3(g)?
The equilibrium constant expression is K = [NH3]^2 / ([N2][H2]^3), reflecting the stoichiometry of the balanced equation (College Board CED).
- 19
What is the effect of dilution on the equilibrium position?
Dilution generally shifts the equilibrium position towards the side with more moles of solute, depending on the specific reaction (College Board CED).
- 20
How is the equilibrium constant affected by the presence of a common ion?
The presence of a common ion shifts the equilibrium position according to Le Chatelier's principle, but does not change the value of K (College Board CED).
- 21
What is the relationship between K and Gibbs free energy?
The relationship is given by ΔG° = -RT ln(K), where a negative ΔG° indicates a spontaneous reaction favoring products (College Board CED).
- 22
How do you calculate K from experimental data?
K can be calculated using the equilibrium concentrations of reactants and products from experimental data, applying the equilibrium constant expression (College Board CED).
- 23
What does it mean if a reaction has a very small K value?
A very small K value indicates that the reaction favors the reactants significantly at equilibrium, meaning very little product is formed (College Board CED).
- 24
Under what conditions can K be used to predict the direction of a reaction?
K can be used to predict the direction of a reaction when comparing Q to K; if Q < K, the reaction proceeds forward, and if Q > K, it proceeds backward (College Board CED).
- 25
What is the equilibrium constant for the reaction SO2(g) + O2(g) ⇌ 2SO3(g)?
The equilibrium constant expression is K = [SO3]^2 / ([SO2][O2]), representing the concentrations at equilibrium (College Board CED).
- 26
How does the equilibrium constant change with the addition of reactants?
Adding reactants shifts the equilibrium position to the right, but does not change the value of K at a constant temperature (College Board CED).
- 27
What is the relationship between partial pressures and Kp?
Kp is expressed in terms of partial pressures of gases, and is related to Kc through the equation Kp = Kc(RT)^(Δn) (College Board CED).
- 28
How does the equilibrium constant relate to the extent of a reaction?
A larger K indicates a greater extent of reaction toward products, while a smaller K indicates a lesser extent toward products (College Board CED).
- 29
What is the effect of pressure changes on gaseous equilibria?
Increasing pressure shifts the equilibrium toward the side with fewer moles of gas, while decreasing pressure shifts it toward the side with more moles (College Board CED).
- 30
What is the equilibrium constant expression for the reaction A + B ⇌ C + D?
The equilibrium constant expression is K = [C][D] / [A][B], based on the balanced equation (College Board CED).
- 31
How does the equilibrium constant change when the coefficients of a reaction are halved?
If the coefficients are halved, the new equilibrium constant K' is the square root of the original K; K' = √K (College Board CED).
- 32
What is the significance of K in predicting product formation?
K provides insight into the favorability of product formation; larger K values suggest a greater likelihood of products being formed at equilibrium (College Board CED).
- 33
What is the effect of temperature on K for an endothermic reaction?
Increasing the temperature for an endothermic reaction results in an increase in the value of the equilibrium constant K (College Board CED).
- 34
How do you determine the direction of a shift in equilibrium?
To determine the direction of a shift, compare the reaction quotient Q to the equilibrium constant K; shifts occur to restore equilibrium (College Board CED).
- 35
What is the equilibrium constant expression for the dissociation of acetic acid?
For the reaction CH3COOH ⇌ H+ + CH3COO-, the equilibrium constant expression is K = [H+][CH3COO-] / [CH3COOH] (College Board CED).