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Kinetics and Reaction Rate
Kinetics and Reaction Rate
As an introduction to this unit, we briefly cover kinetics and reaction rates. These are the factors that control whether or not a reaction occurs, and how quickly a reaction occurs. Typically, there are 5-6 factors controlling reaction collisions.
Notice the graph in the background of this slide - it's important later in the unit!
Reaction collisions are key to reaction products actually being produced! Reactant particles must have the correct activation energy and orientation to create a productive collision.
Temperature plays a key role in creating useful collisions. The higher the temperature, typically the larger fraction of particles that can reach the activation energy necessary for the reaction to occur.
Notice in the following graphs the affect temperature has on molecules reaching the necessary threshold kinetic energy (activation energy) required for the reaction to occur.
Catalysts serve to lower the activation energy required for a reaction to occur. Based on this lowering of threshold energy, more particles can participate in the reaction. Catalysts are typically materials that do not affect the product outcome of the reaction.
Reaction Rates and Temperature - The Arrhenius Theory
Arrhenian Reaction Rate.pdf
Concentration's effect on chemical reaction rate leads us to the second part of this unit - equilibrium. Equilibrium is the point at which a constant concentration is reached for both products and reactants.
Equilibrium
Equilibrium
Equilibrium in a reaction is defined as the point at which...
The rate of the reaction is equal for products and reactants
The concentration (or pressure) of the products and reactants is constant but not necessarily equal
Equilibrium Calculations
Look at the infographic below to see what "K" calculations tell us.
Additional Equilibrium Calculations
"K" can also be calculated based on the pressure of gases in a system.
"Q" can be calculated based on INITIAL concentrations or pressures to determine how a reaction must change to reach equilibrium.
Skeptical Questions In Science
Skeptical Questions In Science
The skeptical question topic for this unit involves equilibrium (homeostasis) processes in the human body. Skeptical questions are thoughtful "Why-based" questions which address biases in scientific material. This type of question is not seeking scientific facts.
The articles associated with this unit are listed below:
Equilibrium "Math Levels"
Equilibrium "Math Levels"
As we move into solving equilibrium situations, one of the biggest problems is knowing what you are solving for. Understanding the equilibrium math level you are working with facilitates higher levels of success with equilibrium problems.
Simply analyzing a known "K" (No calculations or ICE charts are required)
Calculating Kc or Kp based on knowing ALL concentrations or pressures (No ICE chart required)
Solving Kc, Kp, or an unknown concentration based on knowing enough information to create an ICE chart WITHOUT VARIABLES
Solving for Kc, Kp, or unknown concentrations using an ICE chart with variables
ICE Charts
ICE Charts
As equilibrium calculations become more complex, ICE charts (Initial-Change-Equilibrium charts) are a way to keep track of information for a reaction. Knowing how to use an ICE chart to key to successful equilibrium calculations!
ICE Chart Rules
Subtract from reactants and add to products in the change row
Balance coefficients control change ratios
Use a heavy line to separate reactants from products
Molarity is "mol/L" - always divide through by container size if molarity is not given
ICE Chart Practice Progression
EQ Practice 1.pdfEQ Practice 1 Answers.pdfEQ Practice 2.pdfEQ Practice 2 Answers.pdfEQ Practice 3.pdfEQ Practice 3 Answers.pdfEQ Calculation Progression.pdfEQ Calculation Progression Answers.pdfEquilibrium and pH Relationship
Equilibrium and pH Relationship
Equilibrium is key to understanding the difference between strong and weak acids and bases. Strong acids dissociate at a high percentage, while weak acids typically have a much lower ionization. Because of this, weak acids behave like equilibrium reactions. The following sequence helps with understanding equilibrium and pH:
Knowing the auto-ionization of water
Translating the auto-ionization to a weak acid
Using an ICE chart to determine molarities, pH levels, and % ionizations
Students often miss the connection between pH and [H+] or [H3O+] molarity. This connection needs to be calculated. The pH number cannot serve as a direct input into an ICE chart.
pH = -log [H+]
pH = -log [H+]
[H+] = 10^(-)pH
[H+] = 10^(-)pH
Typically in Chemistry 11, we calculate pH based on strong acids only. There are numerous ways to calculate the pH or pOH associated with strong and weak acids and bases. An interesting relationship chart is shown below.
Equilibrium and pH Practice
Ka and pH Practice.pdfKa and pH Practice Answers.pdfLe Chatelier's Principle
Le Chatelier's Principle
Le Chatelier's Principle is a way of determining what will happen in a reaction if that reaction is exposed to various stresses. In terms of equilibrium, it's a way to determine whether reactions will shift toward reactants or products.
Le Chat Notes.pdfLe Chat Charts.pdfLe Chat Practice.pdfLe Chat Practice Answers.pdfEquilibrium of Cobalt Chloride Full Lab
Equilibrium of Cobalt Chloride Full Lab
The purpose of this lab is to investigate factors affecting equilibrium in a reaction that has a visual equilibrium component.
Questions:
"What factors cause the Cobalt chloride reaction to shift towards the reactants vs products?"
"What visual indicators show these shifts occur?"
If-Then-Due-To Hypothesis: "If an equilibrium reaction is exposed to various stresses, the reaction will shift toward reactants or products due to Le Chatelier's Principle."
Variables: (x) stress; (y) reaction shift
Constants: the same cobalt chloride test substance is used throughout the lab
Control: online images (a picture of these is required in the lab)
EQ CoCl2 Lab Notes.pdfLearning-2-Learn and Retrieval Assignments (Required before taking the Unit Graded Test!) and Calibration Test
Learning-2-Learn and Retrieval Assignments (Required before taking the Unit Graded Test!) and Calibration Test
Reaction Rate of Mg + HCl Intro Lab Data and Reflection
Practice (Equilibrium Practice #1-2-3, Ka Practice, Le Chatelier's Practice)
Calibration Practice Test
Big Idea 3 Kinetics and EQ Calibration Test.pdfCalibration Answers
Calibration Answers
The skeptical question/evaluation portion of this answer set is blank because there are multiple ways to answer the question.
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