Question

A 0.200 M NaOH solution was used to titrate a 18.25 mL HF solution. The endpoint was reached after 31.20 mL of titrant were added. Find the molar concentration of the original HF solution.

Answer 1

(31.20 / 18.25) * 0.200 M

Answer 2

so, how many moles in 31.2mL of 0,2M solution?
HF + NaOH = NaF + H2O
You will have that many moles of HF in 18.25mL. Molarity is moles/L