Answer is: the molarity of a solution of HF is 0.73 M.
n(HF) = 4.400 mol; amount of hydrofluoric acid.
V(HF) = 6.00 l; volume of hydrofluoric acid.
c(HF) = n(HF) ÷ V(HF).
c(HF) = 4.400 mol ÷ 6.00 l.
c(HF) = 0.733 mol/l; molarity of a solution (hydrofluoric acid).