Hydrogen and hydroxide concentration

In summary, the concentration of hydroxyl ions present alters in a way that maintains the equilibrium constant (KW) when the amount of hydrogen ions present is increased. This is due to the fact that at equilibrium, the reaction quotient is equal to the equilibrium constant, and this is a property of all chemical equilibria. This can be explained using thermodynamic or kinetic terms, but ultimately, these explanations are based on observed reality. Le Chatelier's principle also applies in this situation, as it describes the observed behavior of systems at equilibrium.
  • #1
nobahar
497
2
This may not even be a valid question, as I may have misunderstood; but here goes...
At 25C, the KW of water is 1 x 10-14 If you increase the amount of hydogen ions present, why does the concentration of hydroxyl ions present alter in such a way that the KW is maintained (i.e. the product of the concentrations of hydrogen and hydroxyl ions)?
If you introduce protons, then they may associate with water to form hydroxonium ions, or they may associate with hydroxyl ions; in the first there will be an incraese in the hydrogen ion concentration, in the second there will be more water formed, which decreases the hydroxyl concentration but does not alter the hydrogen ion concentration. If it was a mixture of the two (that is, if the protons introduced interact with water both water and hroxyl ions), I still can't see how the two concentrations would be balanced so that the KW is maintained.
No textbooks seem to give a reason, which suggests I've misunderstood. Can someone help me with this? :blushing:
 
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  • #2
nobahar said:
why does the concentration of hydroxyl ions present alter in such a way that the KW is maintained

Because that's exactly the way it works?

All chemical equilibria have the same property - at equilbrium reaction quotient equals equilbrium constant. It can be explained in thermodynamical terms (using chemical potentials), it can be explained in kinetic terms (using speeds of forward and backward reactions) - but in fact both explanations just follow the observed reality.

Reality was first, explanations are later :smile:

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  • #3
Am I right in saying that this ties in with Le Chatelier's principle, then?
 
  • #4
Yes, just remember that Le Chatelier's principle also describes reality as it was observed.

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  • #5
Thankyou Borek.
 

Related to Hydrogen and hydroxide concentration

What is the difference between hydrogen and hydroxide concentration?

Hydrogen concentration refers to the amount of hydrogen ions (H+) in a solution, while hydroxide concentration refers to the amount of hydroxide ions (OH-) in a solution. These two ions are responsible for determining the acidity or basicity of a solution.

How is hydrogen and hydroxide concentration measured?

The concentration of hydrogen and hydroxide ions can be measured using a pH scale, which ranges from 0 (most acidic) to 14 (most basic). A solution with a pH of 7 is considered neutral, meaning it has equal concentrations of hydrogen and hydroxide ions.

Why are hydrogen and hydroxide concentration important in chemistry?

Hydrogen and hydroxide concentration play a crucial role in many chemical reactions. They can affect the rate of a reaction, the strength of acids and bases, and the overall pH of a solution. Understanding these concentrations is essential in various fields, from medicine to environmental science.

What factors can influence hydrogen and hydroxide concentration?

The concentration of hydrogen and hydroxide ions can be influenced by several factors, including temperature, pressure, and the presence of other chemicals. In addition, the strength of an acid or base can also impact the concentrations of these ions in a solution.

How can hydrogen and hydroxide concentration be altered?

Hydrogen and hydroxide concentrations can be altered through dilution, which involves adding more water to a solution, or through chemical reactions that produce or consume these ions. The concentration of these ions can also be adjusted using pH buffers, which help maintain a stable pH in a solution.

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