* Logarithmic Scale: The pH scale is a logarithmic scale, meaning each whole number change represents a tenfold change in the concentration of H+ ions. This allows us to express a wide range of acidity and alkalinity in a manageable way.
* Water's Autoionization: Water itself can ionize slightly, producing H+ and OH- ions. The product of their concentrations is a constant (Kw) at a given temperature. At 25°C, Kw = 1 x 10^-14.
* Neutral pH: The neutral pH of 7 corresponds to equal concentrations of H+ and OH- ions in water. This is because the square root of 1 x 10^-14 is 1 x 10^-7, representing the concentration of each ion.
* Extremes:
* pH 1: Represents a very acidic solution with a H+ concentration of 1 x 10^-1 M.
* pH 14: Represents a very basic solution with a H+ concentration of 1 x 10^-14 M.
Why not 1-10?
Using a 1-10 scale would compress the range of acidity and alkalinity. The difference between a pH of 1 and 2 would be much greater than the difference between a pH of 9 and 10. This wouldn't accurately reflect the actual changes in H+ concentration.
In summary:
The pH scale is 1-14 because it's a logarithmic scale based on the concentration of H+ ions in water. This range allows us to express a wide range of acidity and alkalinity while maintaining a consistent relationship between pH values and H+ concentrations.
