29. On the basis of the equation , the pH of  solution of HCl should be 8. However, it is observed to be less than 7.0. Explain the reason.

Concentration  indicates that the solution is very dilute. So, we cannot neglect the contribution of ${\mathrm{H}}_{3}{\mathrm{O}}^{+}$ ions produced from ${\mathrm{H}}_{2}\mathrm{O}$ in the solution. Total . From this we get the value of pH close to 7 but less than 7 because the solution is acidic.
From calculation, it is found that pH of  solution of HCl is equal to 6.96.