Chemistry Equilibrium Constants

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Questions and Answers

Which of the following accurately represents a characteristic of heterogeneous equilibria?

Pure solids do not affect the position of equilibrium. (correct)

All reactants and products are in the same phase.

The equilibrium constant depends on the concentration of pure solids.

The amounts of pure liquids can change the equilibrium position.

What is the main difference between homogeneous and heterogeneous equilibria?

Homogeneous equilibria involve reactions with varying concentrations.

All reactants in homogeneous equilibria are in different phases.

Heterogeneous equilibria always involve gases.

Heterogeneous equilibria include pure solids and liquids. (correct)

When writing equilibrium constant expressions for reactions, which substances are excluded for heterogeneous equilibria?

Aqueous solutions

Solids and liquids (correct)

Gases only

All reactants and products

How is Kp related to Kc in reactions involving gases?

Kp relates to the partial pressures of gases. Signup and view all the answers

Which of the following statements about the decomposition of calcium carbonate is true?

The equilibrium involves both solid and gas phases. Signup and view all the answers

In the decomposition of liquid water to gaseous hydrogen and oxygen, which expression represents Kc?

$K_c = [H_2][O_2]/[H_2O]^2$ Signup and view all the answers

What does the equilibrium constant K represent in reactions involving solutions?

The concentrations of reactants and products. Signup and view all the answers

In calculating Kp from Kc, what factor must be considered?

The temperature of the system. Signup and view all the answers

For the reaction 2NO2(g) ⇌ 2NO(g) + O2(g), what is the equilibrium expression Kp based on the observed pressures?

Kp = (P(NO))^2 * P(O2) / (P(NO2))^2 Signup and view all the answers

Given P(N2) = 0.525 atm, P(NH3) = 0.0167 atm, and P(H2) = 0.00761 atm, does this represent a system at equilibrium for the reaction N2(g) + 3H2(g) ⇌ 2NH3(g)?

Yes, as the ratio of pressures matches Kp. Signup and view all the answers

What does Δn represent in the equation Kp = Kc(RT)Δn?

The difference in moles of products and reactants Signup and view all the answers

In the reaction 2SO2(g) + O2(g) ⇌ 2SO3(g), if Kp = 0.25 at 1100 K, how would you calculate K at the same temperature?

K = Kp / (RT) Signup and view all the answers

When is K equal to Kp according to the relationship Kp = Kc(RT)Δn?

When Δn = 0 Signup and view all the answers

For which of the following reactions is Kp equal to Kc?

C(s) + H2O(g) ⇌ CO(g) + H2(g) Signup and view all the answers

What is the main factor that affects whether Kp or Kc is used in reaction equilibrium calculations?

The physical state of the products and reactants Signup and view all the answers

How is K calculated when Kp is already known for the reaction at a certain temperature?

K = Kp / (RT) Signup and view all the answers

Study Notes

Equilibrium Concepts

Heterogeneous Equilibria: Involve reactants and products in different phases (solid, liquid, gas).
Homogeneous Equilibria: Involve reactants and products in the same phase.

Importance of Pure Substances in Equilibria

Pure solids and liquids are not included in equilibrium expressions because their concentrations remain constant.

Equilibrium Constants

Kc: Equilibrium constant based on concentrations of gaseous and dissolved species.
Kp: Equilibrium constant based on partial pressures of gases.

Conversion Between Kc and Kp

Relationship: ( K_p = K_c (RT)^{\Delta n} )
- ( \Delta n ) is the change in the number of moles of gas: ( (\text{moles of gaseous products}) - (\text{moles of gaseous reactants}) ).
- R = 0.08206 L·atm/(mol·K), T = temperature in Kelvin.

Examples of Equilibrium Expressions

For reactions involving gaseous species, write Kp expressions excluding pure solids and liquids.
Example 1: For the reaction ( 2NH_3(g) + CO_2(g) ⇌ N_2CH_4O(s) + H_2O(g) ), Kp focuses on gaseous components only.

Practice Calculations

Calculate Kp: For ( 2NO_2(g) ⇌ 2NO(g) + O_2(g) ), use given equilibrium pressures to solve for Kp.
Determining Equilibrium: Given pressures, check if Kp reflects a system at equilibrium.

Conditions for Kp and Kc Equality

Kp equals Kc when ( \Delta n = 0 ), indicating the number of moles of gases on both sides of the reaction are equal, causing the ( RT ) factor to cancel.

Examples of When Kp = Kc

Reactions with equal number of gaseous moles on both sides demonstrate the equality of Kp and Kc.

Real-World Application

Understanding equilibrium constants aids in predicting the behavior of chemical reactions under various conditions, critical for industrial processes and chemical synthesis.

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Description

This quiz focuses on writing equilibrium constant expressions, differentiating between heterogeneous and homogeneous equilibria, and converting between Kp and Kc for gaseous reactions. Test your understanding of equilibrium concepts and calculations.