if 50.0 mLs of HCl of unknown concentration is titrated to neutrality with 90.0 mL of .650 M NaOH. calculate the molarity of the HCl

Answer 1

NaOH and HCl react 1:1 so you can use the simplified equation
mL NaOH + M NaOH = mL HCl x M HCl

Answer 2

1.17M