Equilibrium Constants in Chemical Reactions

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Questions and Answers

What is the equilibrium constant Kc for Experiment 1 based on the given concentrations?

0.213

0.211 (correct)

0.0400

0.0243

What is the equilibrium constant expression Kc for the reaction 2 O3(g) Δ 3 O2(g)?

$K_c = \frac{[O_2]^3}{[O_3]^2}$ (correct)

$K_c = \frac{[O_3]}{[O_2]^2}$

$K_c = \frac{[O_3]^2}{[O_2]^3}$

$K_c = \frac{[O_2]^2}{[O_3]}$

Which of the following statements is true regarding the equilibrium constants Kc from different experiments?

Kc varies significantly with the concentration of reactants.

Kc remains constant despite the variations in initial concentrations. (correct)

Kc can only be calculated when starting with NO2.

Kc shows different values depending on temperature.

Which of the following is the correct equilibrium expression Kc for the reaction 2 NO(g) + Cl2(g) Δ 2 NOCl(g)?

$K_c = \frac{[NOCl]^2}{[NO]^2[Cl_2]}$ (C) Signup and view all the answers

What is the Kc expression for the reaction Ag+(aq) + 2 NH3(aq) Δ Ag(NH3)2+(aq)?

$K_c = \frac{[Ag(NH_3)_2^+]}{[Ag^+][NH_3]^2}$ (B) Signup and view all the answers

For the reaction H2(g) + I2(g) Δ 2 HI(g), what is the correct expression for Kc?

$K_c = \frac{[HI]^2}{[H_2][I_2]}$ (D) Signup and view all the answers

What is a characteristic of Kc values mentioned in the content?

Kc is dimensionless and has no units. (C) Signup and view all the answers

What is the correct equilibrium expression for the reaction Cd2+(aq) + 4 Br-(aq) Δ CdBr42-(aq)?

$K_c = \frac{[CdBr_4^{2-}]}{[Cd^{2+}][Br^-]^4}$ (A) Signup and view all the answers

What principle explains how a system at equilibrium responds to disturbances?

Le Chatelier’s Principle (C) Signup and view all the answers

What occurs if a reactant is removed from a system at equilibrium?

The system reacts to produce more of the removed reactant. (C) Signup and view all the answers

If the volume of a gaseous equilibrium mixture is reduced, what direction will the system shift?

It shifts toward the side with fewer moles of gas. (D) Signup and view all the answers

Which factor does not affect the equilibrium position of a chemical reaction?

Presence of a catalyst (C) Signup and view all the answers

In a reaction producing NH3 from H2 and N2, increasing the concentration of N2 will result in what response from the system?

The system will produce more NH3. (B) Signup and view all the answers

Which statement about equilibrium is false?

Equilibrium is only established in solutions. (C) Signup and view all the answers

How does the equilibrium constant Kp change if the reaction 2 HI(g) Δ H2(g) + I2(g) is rewritten as 6 HI(g) Δ 3 H2(g) + 3 I2(g)?

Kp is raised to the power of 3 (A) Signup and view all the answers

What is the correct equilibrium constant expression for the reaction 2 NOBr(g) Δ 2 NO(g) + Br2(g)?

Kc = [NO]^2 / [NOBr]^2 (B) Signup and view all the answers

How can the equilibrium constant for a net reaction be calculated using separate reactions?

By multiplying the equilibrium constants of the individual reactions (A) Signup and view all the answers

What is the relationship between the equilibrium constants of a reaction and its reverse reaction?

The reverse reaction's constant is the inverse of the forward reaction (B) Signup and view all the answers

For which of the following scenarios can the equilibrium constants be multiplied to find a new constant?

When the reactions are added together (D) Signup and view all the answers

Which of the following is true about the expression for Kc in the reaction 2 Br2(g) + Cl2(g) Δ 2 BrCl(g)?

Kc = [BrCl]^2 / [Br2]^2[Cl2] (D) Signup and view all the answers

What happens to the overall Kc when a reaction is reversed?

Kc becomes the reciprocal (D) Signup and view all the answers

What is the activity of any pure solid or liquid in terms of its reference value?

1 (C) Signup and view all the answers

In the equilibrium-constant expression for the evaporation of water, which component is omitted?

H2O(l) (B) Signup and view all the answers

Which of the following reactions would have an equilibrium-constant expression that includes only gases?

C(s) + O2(g) Δ CO2(g) (B) Signup and view all the answers

For the decomposition of calcium carbonate, what does the equilibrium constant Kc equal to?

[CO2] (B) Signup and view all the answers

What remains constant for the equilibrium of CaCO3, CaO, and CO2 regardless of their amounts?

Partial pressure of CO2 (B) Signup and view all the answers

In the reaction SnO2(s) + 2 CO(g) Δ Sn(s) + 2 CO2(g), which components are included in the equilibrium constant expression?

CO(g) and CO2(g) (A) Signup and view all the answers

Which statement about equilibrium constants in heterogeneous reactions is correct?

Concentrations of pure solids and liquids are omitted. (A) Signup and view all the answers

What is the correct equilibrium-constant expression Kc for the reaction CO2(g) + H2(g) Δ CO(g) + H2O(l)?

[CO] / [CO2] (A) Signup and view all the answers

How does an increase in temperature affect an endothermic reaction at equilibrium?

The equilibrium shifts right to produce more products. (A) Signup and view all the answers

What will happen to the equilibrium if a product is removed from an exothermic reaction?

The equilibrium will shift left to produce more reactants. (A) Signup and view all the answers

When pressure is increased in a system at equilibrium, which direction does the equilibrium shift if there are fewer moles of gas on the product side?

The equilibrium shifts right to favor the products. (C) Signup and view all the answers

If the temperature of an exothermic reaction is decreased, what is the effect on the equilibrium position?

The equilibrium shifts right to produce more products. (A) Signup and view all the answers

Which of the following defines Le Châtelier’s principle?

An equilibrium shifts to counteract a change applied to it. (C) Signup and view all the answers

Study Notes

Chemical Equilibrium

Equilibrium is a state of balance where the rate of the forward reaction equals the rate of the reverse reaction.
Static equilibrium is a state where objects are at rest.
Dynamic equilibrium is a state where opposing processes occur at equal rates, maintaining constant net change.
Chemical equilibrium is a state where the rates of the forward and reverse reactions are equal, and the concentrations of reactants and products remain constant.

Calculating Equilibrium Constants

Equilibrium constants (K) can be calculated from equilibrium concentrations of reactants and products.
Equilibrium constants can predict equilibrium concentrations and the direction of a reaction to reach equilibrium.

Le Chatelier's Principle

Le Chatelier's principle predicts how a system at equilibrium responds to changes in concentration, volume, pressure, and temperature.
Adding a reactant causes the system to shift in the direction that consumes more reactant to reduce the concentration of the newly added reactant.
Conversely, removing a substance causes the system to shift in the direction that produces more of that substance.
Increasing pressure (decreasing volume) causes the equilibrium to shift to the side with fewer moles of gas.
Decreasing pressure (increasing volume) causes the equilibrium to shift to the side with more moles of gas.
Increasing temperature favors the endothermic reaction.
Decreasing temperature favors the exothermic reaction.

The Equilibrium Constant, K

The value of K reflects the relative concentrations of reactants and products at equilibrium.
A large K indicates that the products are largely favored in an equilibrium, whereas a small K indicates that reactants are favored.
If K is large (>>1), the equilibrium lies far to the right, favoring the products.
If K is small (<<1), the equilibrium lies far to the left, favoring the reactants.

Equilibrium Constant Expressions

Equilibrium expressions relate the concentrations of products and reactants at equilibrium.
For the generic reaction aA + bB → cC + dD, the equilibrium constant expression is: Kc = [C]^c[D]^d / [A]^a[B]^b.
A homogeneous equilibrium has all reactants and products in the same phase.
A heterogeneous equilibrium has reactants or products in different phases, with pure solids and liquids not included in the equilibrium expression.

Heterogeneous Equilibria

Equilibrium concentrations vary with changes in temperature.
Equilibrium expressions can be modified by changing the stoichiometric coefficients of the chemical reactions.

Relating Chemical Equation Stoichiometry and Equilibrium Constants

Multiplying or dividing a balanced reaction equation by a factor modifies the equilibrium constant (raising it to that power).
If two reactions add up to give a net reaction, their equilibrium constants multiply.

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Description

Test your understanding of equilibrium constants Kc through various experiments and reactions. This quiz covers the expressions for Kc, concentration comparisons at equilibrium, and the effects of temperature changes on equilibrium. Perfect for chemistry students studying reaction dynamics and equilibrium.