The relative molecular weight of Na is 23, and that of Cl is 35.5, which adds up to 58.5g/mol.

Molarconcentration/Molarity is a common expression of solution concentration, which is defined as the amount of solute B in the solution divided by the volume of the mixture, referred to as concentration for short, and expressed by symbol c(B). The mathematical expression is m (mol/l) = n (mol)/v.

Also known as molar concentration.