could you help me to explain why doesn't the pH change when we dilute it with water? thanks
When something is diluted you change both the concentrations of acid and base but the ratio is still the same
When you dilute something you are just spreading it out more
An acid diluted DOES change the pH.
A base diluted DOES change the pH.
For example, 0.1 M HCl has a pH of 1.
Dilute that by a factor of 2 and the concn = 0.05. The pH of that solution is -log(0.05) = 1.30
Certainly! When we dilute a solution with water, the pH usually remains the same. This is because pH is a measure of the concentration of hydrogen ions (H+) in a solution, and dilution does not change the concentration of H+ ions.
To understand this, let's consider the definition of pH. The pH scale ranges from 0 to 14, where a pH of 7 is considered neutral, below 7 is acidic, and above 7 is alkaline or basic. pH is calculated based on the concentration of H+ ions, which is determined by the dissociation of water molecules.
In pure water, a small fraction of water molecules naturally dissociate into hydrogen ions (H+) and hydroxide ions (OH-). This equilibrium is represented by the equation:
H2O ⇌ H+ + OH-
However, the dissociation of water is very minimal, and the concentration of H+ ions in pure water is extremely low (about 10^-7 moles per liter). This corresponds to a pH of 7, which is why pure water is considered neutral.
Now, when we dilute an acidic or basic solution with water, the concentration of H+ ions from the solute remains the same, but the overall volume of the solution increases. Since pH is calculated based on concentration (moles/liter), decreasing the volume while maintaining the same number of moles will not change the concentration of H+ ions. As a result, the pH remains constant even after dilution.
To summarize, when we dilute a solution with water, the pH remains unchanged because the concentration of H+ ions, which determines the pH, is not affected by dilution.