If 27.31mL of 0.2115 M NaOH is able to nuetralize 37.45mL of HCI what is the concentration of the acid?

Taking into account that

Normality of NaOH = N1=0.2115 N

Volume of NaOH = V1=27.31 ml

Normality of HCl = N2=x N

Volume of HC l=37.45 ml

We may proceed like this:

V1*N1=V2*N2 27.31*0.2115=37.45*x, x=0.1542 N=0.1542 M.

Concentration of HCl = 0.1542 moles/liter.

Hope this is good for you