Equilibrium: Chemical and Dynamic

An error occurred trying to load this video.

Try refreshing the page, or contact customer support.

Coming up next: LeChatelier's Principle: Disruption and Re-Establishment of Equilibrium

You're on a roll. Keep up the good work!

Take Quiz Watch Next Lesson
Your next lesson will play in 10 seconds
  • 0:05 Chemical Equilibrium
  • 1:36 Equilibrium Constant
  • 3:44 Examples
  • 5:36 Lesson Summary
Save Save Save

Want to watch this again later?

Log in or sign up to add this lesson to a Custom Course.

Log in or Sign up

Speed Speed

Recommended Lessons and Courses for You

Lesson Transcript
Instructor: Amy Meyers

Amy holds a Master of Science. She has taught science at the high school and college levels.

Learn the definition of chemical equilibrium and how it is dynamic. Discover what the equilibrium constant is and how it shows whether the reaction favors the reactants or products. Learn how chemists designate equilibrium in an equation and how they show the difference in reaction rate.

Chemical Equilibrium

Chemical equilibrium is when the rate of a forward reaction equals the rate of the reverse reaction and the concentrations of the products and reactants remain unchanged. Equilibrium is a dynamic state, meaning that things are always moving. Products are being broken down into reactants, and reactants are being combined into products. Things are moving, but the concentrations stay the same. When the reaction is written, it is written with a double arrow instead of an equal sign to show that the reaction is reversible. A + B go to C + D.

In some reactions, the forward reaction is almost completed before the reverse reaction starts. In this case, there's a higher concentration of products than reactants, but the reaction can still be in equilibrium because the concentrations of both the reactants and products stay the same. The reaction equilibrium lies to the right because there are more products than reactants. In this case, the reaction is written with two different-length arrows, with the longer arrow pointing to the right, showing that more product is made than reactant. A + B goes to C + D.

The opposite is also true. The forward reaction of making products has barely started, and the reverse reaction is already going like gangbusters. In this case, the equilibrium of the reaction is said to lie to the left and the longer arrow points left. A + B goes to C + D.

Equilibrium Constant

The rate of reactions are often shown in a graph like this one. This graph compares the rate of the forward reaction to the rate of the reverse reaction. To start, the forward reaction has the maximum rate possible, and the reverse reaction has no rate because it hasn't started yet. As the reaction is under way, the forward reaction decreases as the reactants are used up, and the reverse reaction increases as there is more product to turn back into reactants. Eventually, equilibrium is reached, and the graph turns into one straight horizontal line.

Once equilibrium is reached, the concentrations of the reactants and products don't change. When this happens, an equilibrium constant K can be written for the reaction. Only the substances whose concentrations change are included in the equilibrium constant equation. If the reaction equation is nA + mB goes to xC + yD, then the equilibrium constant equation can be written as:


To unlock this lesson you must be a Study.com Member.
Create your account

Register to view this lesson

Are you a student or a teacher?

Unlock Your Education

See for yourself why 30 million people use Study.com

Become a Study.com member and start learning now.
Become a Member  Back
What teachers are saying about Study.com
Try it risk-free for 30 days

Earning College Credit

Did you know… We have over 200 college courses that prepare you to earn credit by exam that is accepted by over 1,500 colleges and universities. You can test out of the first two years of college and save thousands off your degree. Anyone can earn credit-by-exam regardless of age or education level.

To learn more, visit our Earning Credit Page

Transferring credit to the school of your choice

Not sure what college you want to attend yet? Study.com has thousands of articles about every imaginable degree, area of study and career path that can help you find the school that's right for you.

Create an account to start this course today
Try it risk-free for 30 days!
Create an account