Answer:
[tex]0.3456\ \text{M}[/tex]
Explanation:
[tex]V_1[/tex] = Volume of NaOH = 34.56 mL
[tex]V_2[/tex] = Volume of HCl = 25 mL
[tex]M_1[/tex] = Concentration of NaOH = 0.25 M
[tex]M_2[/tex] = Concentration of HCl
When endpoint is reached the number of moles of NaOH will be equal to the number of moles of HCl
[tex]M_1V_1=M_2V_2\\\Rightarrow M_2=\dfrac{M_1V_1}{V_2}\\\Rightarrow M_2=\dfrac{0.25\times 34.56}{25}\\\Rightarrow M_2=0.3456\ \text{M}[/tex]
Concentration of HCl is [tex]0.3456\ \text{M}[/tex].