Hello!
The neutralization equation of HCl and NaOH is the following:
HCl + NaOH → NaCl + H₂O
If 5 mL of 0,2 M HCl were required to neutralize exactly 10 mL of NaOH we can use the following equation (mole equivalency at equivalence point) to find the concentration of the base:
[tex]moles NaOH=moles HCl \\ \\ C NaOH*VNaOH=C HCl * V HCl \\ \\ C NaOH= \frac{CHCl*VHCl}{V NaOH}= \frac{0,2 M * 5 mL}{10 mL}=0,1 M [/tex]
So the concentration of NaOH is 0,1 M
Have a nice day!
