Hello Everyone, thanks for stopping by to see my post on the equilibrium constant of water. I'm so glad my posts on chemistry topics can be helpful to you.
Why you should understand Kw: Kw describes the autoionization of water and is important to the equilibrium of weak acids and bases in solution.
Key Ideas
- What is Kw?
- Where does it Kw come from?
- Why is it useful?
What is Kw?
Kw is the equilibrium constant of water. It describes how much water has dissociated into hydronium and hydroxide when water is simply sitting in a container by itself. This dissociation without an external influence is called "autoionization" because it is an automatic ionization. Kw describes the automatic ionization of water that occurs on its own.
Above is the expression for the Kw, which is the concentration of hydronium multiplied by the concentration of hydroxide. Water is not included in this expression because water is a liquid. Recall that liquids and solids are not included in equilibrium expressions.
Where does Kw come from?
Kw is the equilibrium expression of water, meaning it is written like any other equilibrium expression. Products are placed in a fraction over the reactants. In the autoionization of water, water breaks down into hydronium and hydroxide. Hydronium and hydroxide are your products and water is the reactant. Water is a liquid and is not included in the equilibrium constant expression.
Why is it useful?
Kw relates the concentrations of hydronium and hydroxide. When trying to convert from one concentration to another, like when using the happy fun wheel, Kw can be very useful. Rather than going around the entire wheel and doing excessive conversions, Kw can get you from the concentration of hydronium to hydroxide (and vise versa) in one calculation.
To the left is the happy fun wheel, and at the very bottom of the square is the conversion between hydronium and hydroxide concentration using Kw.
Summary
- Kw is the equilibrium constant of water.
- In the autoionization of water, water breaks down into hydronium and hydroxide.
- Kw relates the concentrations of hydronium and hydroxide.
I hope you've found this post on Kw helpful. If you have any questions feel free to comment on this post, email me, or comment on the video I've linked below.
- Saren
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