After calculating the mass of NaOH to make the approximate 0.2mol/L solution, why is it not crucial to weigh out an exact amount?

Answer 1

Can't you vary the volume of solution? Measuring out an amount of solute is much easier than measuring out a specific mass.

Answer 2

In addition to the answer by Bob Pursley, we also recognize that NaOH is not a pure substance (at least not for very long) as it pickes up CO2 and H2O from the atmosphere.