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What Is The Dissociation Constant Of Water At 25 C? It’s a fundamental concept in chemistry that dictates how much water naturally breaks down into its constituent ions, hydrogen (H+) and hydroxide (OH-). Understanding this constant is vital for comprehending acidity, alkalinity, and countless chemical reactions that occur in aqueous solutions. Let’s dive in and explore this essential value.
Delving into the Dissociation Constant (Kw) of Water
The dissociation of water is an equilibrium process, meaning that water molecules are constantly breaking apart into ions and reforming. This can be represented by the following equation: H2O <=> H+ + OH-. The equilibrium constant for this reaction is called the ion product of water, often denoted as Kw. This Kw value specifically at 25°C is approximately 1.0 x 10-14. This seemingly small number has huge implications.
Think of Kw as a seesaw. On one side, you have the concentration of hydrogen ions (H+), and on the other, the concentration of hydroxide ions (OH-). Kw tells us the product of these two concentrations *must* equal 1.0 x 10-14 at 25°C. This leads to some important relationships:
- In pure water, the concentration of H+ equals the concentration of OH-.
- Since their product is 1.0 x 10-14, each concentration is 1.0 x 10-7 M (Molar).
- Any shift in H+ concentration (like adding an acid) *must* cause a corresponding decrease in OH- concentration to maintain Kw.
Temperature is a critical factor affecting Kw. While at 25°C, Kw is 1.0 x 10-14, this value changes at different temperatures. For example, at higher temperatures, the dissociation of water increases, and Kw becomes larger. Conversely, at lower temperatures, the dissociation decreases, and Kw becomes smaller. This is why it’s vital to specify the temperature when discussing the dissociation constant of water.
Want to explore more about the specifics and get access to equations about the topic we talked about? We suggest you review a chemistry textbook or a reliable online resource like LibreTexts for an in-depth explanation and further examples.