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Ch.7 Energy, Rate and EquilibriumWorksheetSee all chapters

# Rate of Reaction

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Sections
Nature of Energy
First Law of Thermodynamics
Endothermic & Exothermic Reactions
Bond Energy
Thermochemical Equations
Heat Capacity
Thermal Equilibrium (Simplified)
Hess's Law
Rate of Reaction
Energy Diagrams
Chemical Equilibrium
The Equilibrium Constant
Le Chatelier's Principle
Solubility Product Constant (Ksp)
Spontaneous Reaction
Entropy (Simplified)
Gibbs Free Energy (Simplified)

The Rate of Reaction examines how quickly reactants break down to form products.

###### Chemical Reactions & Kinetics

Concept #1: Understanding Chemical Kinetics.

Transcript

Hey, guys! In this brand new set of videos, we're going to take a look at the rates of chemical reactions.
Now we're going to say that chemical kinetics is basically the study of reaction rates. And when we say rates we're really talking about speed. We're going to say the word kinetic comes from the Greek word kinesis, and in Greek, kinesis just means motion. And remember, attached to motion is speed, so chemical kinetics is looking at how fast are reactants or products are changing over a period of time. So that's all kinetics really is and that's what rate is, so rate is tied to speed.
And we're going to say up to this point, hopefully, we all remember stoichiometry, so we've learned how to calculate the limiting reactant amount. We've learned to calculate the theoretical yield. Now it's up to us to figure out the rates of these reactions. Figure out how fast are my compounds reacting in my balanced chemical equation.

The word “kinetics” is derived from the Greek word “kinesis”, which means motion. So Chemical Kinetics deals with the speed of motion experienced by reactants as they are allowed to react.

Concept #2: Kinetics in a Chemical Reaction.

Transcript

We're going to say fundamentally when looking at any balanced equation, here we have a simple one. A is changing into N. A could be any type of compound. B could be any type of compound. But fundamentally, this is a balanced chemical equation. We're going to say when looking at any chemical equation, we're going to say in the simplest way it's just our reactants breaking down to give us products.
If we take a look at the time elapsed, when we start out, it’s 0 seconds. Initially all we have are the white balls. Those are A. In the beginning, before a reaction is even allowed to start, we have only reactants. Take a look. Over time, what begins to happen? Over time, you’re going to get more and more of compound B, our product forming.
The more our product forms, the less reactant we’re going to have around because remember, the products are made from our reactants breaking down. Eventually, we’ll say that our reaction reaches completion. We’re going to say when a reaction reaches completion, basically almost all of the reactants are gone and all we have are products.
We're going to say for reactions that go to completion, we have one single arrow going forward. Later on, we’re going to learn about reactions that don't reach completion but actually reach equilibrium. At those states, we're not going to have a single arrow going forward. We're going to have two arrows. One is going forward and one is going backwards.
We're going to say when we have double arrows we’re at equilibrium. When we get to states of equilibrium, we don't get rid of our reactants. Eventually we're going to have some reactants and products basically living in harmony with each other, living in equilibrium. For now, we're just going to be worried about reactions going to completion but eventually we’re going to get to the point where we should realize that sometimes chemical reactions go to equilibrium.

A chemical reaction is simply reactants breaking down and reassembling to form products.

###### Factors Influencing Reaction Rates

Depending on certain conditions, a chemical reaction can either happen very quickly in seconds or take place over several years.

Concept #3: Slow vs. Fast Reactions.

Concept #4: Kinetics & the Concentration of Compounds.

In order for a chemical reaction to occur two molecules must collide. The more concentrated a solution then the greater the chance of them colliding.

Concept #5: Kinetics & the Surface Area of Compounds.

For a collision between molecules to be successful, molecules join at their active sites. The larger their surface area then the more places the molecules can successful join.

Concept #6: Kinetics & Temperature.

The General Rule is increasing the reaction temperature by 10oC will cause the rate to double.

Concept #7: Kinetics & the Catalyst.

A catalyst helps to speed up the rate of a reaction by lowering the energy of activation (Ea).