Ch.14 - Chemical EquilibriumSee all chapters
All Chapters
Ch.1 - Intro to General Chemistry
Ch.2 - Atoms & Elements
Ch.3 - Chemical Reactions
BONUS: Lab Techniques and Procedures
BONUS: Mathematical Operations and Functions
Ch.4 - Chemical Quantities & Aqueous Reactions
Ch.5 - Gases
Ch.6 - Thermochemistry
Ch.7 - Quantum Mechanics
Ch.8 - Periodic Properties of the Elements
Ch.9 - Bonding & Molecular Structure
Ch.10 - Molecular Shapes & Valence Bond Theory
Ch.11 - Liquids, Solids & Intermolecular Forces
Ch.12 - Solutions
Ch.13 - Chemical Kinetics
Ch.14 - Chemical Equilibrium
Ch.15 - Acid and Base Equilibrium
Ch.16 - Aqueous Equilibrium
Ch. 17 - Chemical Thermodynamics
Ch.18 - Electrochemistry
Ch.19 - Nuclear Chemistry
Ch.20 - Organic Chemistry
Ch.22 - Chemistry of the Nonmetals
Ch.23 - Transition Metals and Coordination Compounds
Sections
Chemical Equilibrium
ICE Chart
Le Chatelier's Principle
The Reaction Quotient
Additional Sections
Equilibrium Expressions

In order to calculate the equilibrium concentrations of compounds we need to use an ICE Chart. 

Calculating Equilibrium Concentrations

Concept #1: Understanding an ICE Chart 

An ICE Chart should be used when we are missing more than one equilibrium amount for compounds in our balanced equation. 

Since our equilibrium constant K is involved in an ICE Chart then we must continue to ignore solids and liquids. 

Example #1: We have a solution where Ag(CN)2 (g), CN (g), and Ag+ (g) have an equilibrium constant, K, equal to 1.8 x 10-19. If the equilibrium concentrations of Ag(CN)2 and CN are 0.030 and 0.10 respectively, what is the equilibrium concentration of Ag+?

Example #2: We place 2.5 mol of CO and 2.5 mol of CO3 in a 10.0 L flask and let the system come to equilibrium. What will be the final concentration of CO2?  K = 0.47

Practice: For the reaction: N2 (g) + 2 O2 (g) ⇌ 2 NO2 (g), Kc = 8.3 x 10 -12 at 25°C. What is the concentration of N2 gas at equilibrium when the concentration of NO2 is twice the concentration of O2 gas?

Example #3: When 0.600 atm of NO­­2 was allowed to come to equilibrium the total pressure was 0.875 atm. Calculate the Kof the reaction. 

Example #4: An important reaction in the formation of acid rain listed below.

2 SO2 (g)   +  O2 (g)  ⇌  2 SO3 (g)

Initially, 0.023 M SO2 and 0.015 M O2 are mixed and allowed to react in an evacuated flask at 340 oC. When an equilibrium is established the equilibrium amount of SO3 was found to be 0.00199 M. Calculate the equilibrium constant, Kc, for the reaction at 340 oC. 

Example #5: If Kc is 32.7 at 300oC for the reaction below:

H2 (g) +  Br2 (g) ⇌  2 HBr (g) 

What is the concentration of H2 at equilibrium if a 20.0 L flask contains 5.0 mol HBr initially?

Practice: At a given temperature the gas phase reaction: H2 (g) + O2 (g) ⇌ 2 NO (g) has an equilibrium constant of 4.00 x 10 -15. What will be the concentration of NO at equilibrium if 2.00 moles of nitrogen and 6.00 moles oxygen are allowed to come to equilibrium in a 2.0 L flask.

Example #6: Consider the following reaction:

COBr(g)  ⇌  CO (g) + Br(g)

A reaction mixture initially contains 0.15 M COBr2. Determine the equilibrium concentration of CO if Kc for the reaction at this temperature is 2.15 x 10-3.