A mixture is made using A 50.0 mL sample of a 0.20 M aqueous solution of NAOH was added to 50.0 mL of a 0.20 M aqueous solution of HCl.What is its pH at 25.0 °C?

mols NaOH = M x L = 0.01

mols HCl = M x L = 0.01

NaOH + HCl ==> NaCl + H2O
0.01...0.01
So you will form 0.01 mols NaCl and have just NaCl and H2O in the solution at the end; therefore, the pH will be that of pure H2O.