Given:
Volume of each of the solutions = 100 mL of each
Concentration of HCl = 0.10 M
Concentration of HNO3 = 0.10 M
Concentration of NaOH = 0.10 M
If all are mixed in one solution, the pH will surely be low since there are two acids mixed with one base. The pH range should be 1 - 5.