Why does pH decrease when diluting a base? [closed]








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* Take a strong base such a sodium hydroxide
* Adding water will result in adding a hydroxide ions as well as hydronium ions to the solution
* However if the pH decreases this means that the hydronium ion concentration will increase , hence the hydroxide ion concentration decreased
* Why is this so ? What about all the hydroxide ions that were added from the water
* I understand the mathematics behind it , but it doesn't intuitively make sense




You are overcomplicating it. The concept of pH and pOH stems from the concentration of $\ce{OH-}$ or $\ce{H+}$ per solvent unit $\ce{H2O}$, like so $\ce{\frac{[OH-]}{[H2O]}}$ or $\ce{\frac{[H+]}{[H2O]}}$. There is also a logarithm involved, but lets keep it simpler than that. **You are adding far more of the denominator** than the numerator, hence the fraction is becoming smaller and the pH is going towards pH of pure water. 


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