The precise pH value of a 0.1 mol solution of sodium hydroxide (NaOH) is 13.1. This value is derived from the fact that sodium hydroxide is a strong base, which means it completely dissociates in water to produce hydroxide ions (OH-) in a 1:1 ratio. The concentration of hydroxide ions in the solution is therefore 0.1 mol/L. The pH scale is a logarithmic scale used to express the acidity or basicity of an aqueous solution, with a pH of 7 being neutral. Since the concentration of hydroxide ions is directly related to the pH, we can calculate the pH using the formula pH = 14 + log[OH-]. Plugging in the concentration of hydroxide ions (0.1 mol/L), we get pH = 14 + log(0.1) = 14

1 = 13.1.

The reason for this precise pH value lies in the properties of sodium hydroxide as a strong base. Strong bases, such as sodium hydroxide, dissociate completely in water, leading to a high concentration of hydroxide ions. This high concentration of hydroxide ions results in a low pH value, indicating a strongly basic solution. The pH of a solution is determined by the concentration of hydrogen ions (H+), which are inversely proportional to the concentration of hydroxide ions. In the case of sodium hydroxide, the high concentration of hydroxide ions leads to a low concentration of hydrogen ions, resulting in a high pH value.

According to the pH scale, a pH value of 13.1 is considered strongly basic. This is consistent with the behavior of sodium hydroxide as a strong base. Additionally, the pH value of a 0.1 mol solution of sodium hydroxide can be confirmed through experimental measurements using pH meters or pH indicator papers. These measurements are typically accurate to within a few tenths of a pH unit, which is consistent with the calculated value of 13.1.

In conclusion, the precise pH value of a 0.1 mol solution of sodium hydroxide is 13.1, which is a result of the complete dissociation of sodium hydroxide in water, leading to a high concentration of hydroxide ions and a low pH value. This value is consistent with the behavior of sodium hydroxide as a strong base and can be confirmed through experimental measurements.