By titration it is found that 68.5 ml of 0.154 m naoh (aq) is needed to neutralize 25.0 ml of hcl (aq). calculate the concentration of the hcl solution.

The reaction of NaOH and HCl follows: NaOH + HCl ⇒NaCl + H2O.

So the ratio between the reactants is 1:1.

The moles of NaOH needed to neutralize the acid = volume of NaOH solution * concentration of NaOH solution = 0.0685 L * 0.154 M = 0.01055 mole.

Therefore 0.01055 moles of HCl is presented in the acid solution.

The concentration of HCl solution = moles of HCl/volume of HCl solution = 0.01055mole/0.025L = 0.422 M