On the basis of the equation pH = - log [H^(+)], the pH of 10^(-8) mol dm^(-3) solution of HCl should be 8. However, it is observed to be less than 7.0 . Explain the reason.

On the basis of the equation pH = - log [H^(+)], the pH of 10^(-8) mol

1.	On the basis of the equation pH = - log [H^(+)], the pH of 10^(-8) mol dm^(-3) solution of HCl should be 8. However, it is observed to be less than 7.0 . Explain the reason.
Answer» Solution :pH of `10^(-8)` M HCl solution is not8 because this concentration is so low that `H^(+)` ion produced from `H_(2)O` in the solution (VIZ. `10^(-7)M`) connot be neglected. Total `[H^(+)] = 10^(-8) + 10^(-7)`M. SOLVING and calculating pH, we GET the value close to 7 but les than 7 as the solution is ACIDIC