Question

(ii) Write the pH value of pure water.

Hint:

A pH value of 7 indicates neutrality, where the concentrations of hydrogen and hydroxide ions are equal in pure water.

Answer 1

The pH value of pure water is 7. This is because, in pure water, the concentration of hydrogen ions (\(H^+\)) and hydroxide ions (\(OH^-\)) are equal, both being \(10^{-7}\) mol/L at 25°C. The pH is calculated as: \[ \text{pH} = -\log [H^+] \] Since \([H^+] = [OH^-] = 10^{-7}\) mol/L for pure water, we get: \[ \text{pH} = -\log (10^{-7}) = 7 \] Thus, the pH value of pure water is 7, which is considered neutral.