Answer:
Mass percent of Na
Explanation:
To conclusively prove that a substance is NaCl, we must look at its percentage composition.
There is a standard and known percentage by mass composition of NaCl which has been documented in literature. Every other sample of NaCl is analyzed in comparison to these values of which the purity of the NaCl is a major determinant.
Hence, by considering the percentage by mass of the constituent elements, the purity of a sample of any compound can be conclusively established.
