47 In a titration, 20.0 milliliters of a 0.150 M NaOH (aq) solution exactly neutralizes 24.0 milliliters of an HCl (aq) solution. What is the concentration of the HCl (aq) solution? (1) 0.125 M (3) 0.250 M

(2) 0.180 M (4) 0.360 M

The answer is (1) 0.125 M. The reaction equation is NaOH + HCl = NaCl + H2O. So the mol number of NaOH and HCl is the same. So suppose the concentration of HCl is x, we can have equation: 20*1.15=24*x. So x = 0.125 M. (M means mol/L, but if we use the same unit at both side of the equation, it is ok.)