Answer
1.1
Work Step by Step
pH = [H]
[H] =[HCl], because HCl dissociates completely
[HCl] is 2.5 moles per liter or 0.0025 in one mL:
For 3 mL it is 0.0075 moles
3 mL is diluted to 100 mL
So, 0.0075 moles in 100 mL or 0.075 moles per liter
Final [HCl] = 0.075 M = [H]
pH= -log [$7.5\times10^{-2}$] = 1.1
