The pH of the solution after addition of 50.0ml is 0.1003
pH is known as the negative logarithm of the hydrogen ion concentration in a solution.
In the given condition we have 100 ml of sample of 0.18 molar of HclO4 titrated with 0.27m LioH.
pH = log[H+]
= log [Hclo4]
Mole of Hclo4 0.1 L * 0.18 m = 0.018 M
mol LiOH = 0.1 L * 0.27 m = 0.027 M
total volume = 0.1L + 0.1L = 0.2L
HClO4] = (0.018-0.0081) /0.2 L
= -1.26 billion
PH = -㏒ -1.26
= 0.1003
So, the pH of the solution after adding 100 ml of liquid is 0.1003