Why is it more accurate to say that the concentration of a solution of acetic acid is 0.01 f rather than 0.01 m?

The formal concentration accounts for the moles of the original chemical formula into the solution rather than the concentration of the species that actually exist in solution which is accounted for by the molarity.

Explanation:

Hello,

In this case, the difference between formal and molar units of concentration  lies on the fact that the formal concentration accounts for the moles of the original chemical formula into the solution rather than the concentration of the species that actually exist in solution which is accounted for by the molarity. In such a way, since acetic acid is partially dissociated, formality better explains there are 0.01 moles of acetic acid added to the solution including both the non-dissociated and dissociated constituents. However, molarity just accounts for the 0.01 moles of acetic acid that could or could not have been dissociated into the solution.

As you see, this is just a by concept difference, as they lead to suitable calculations.

Best regards.