We let the empirical formula for the compound compost of sodium and chlorine as NaxCly. The molar mass of the empirical equation is,
23x + 35y
The percentages,
Na: 0.40 = 23x/ (23x + 35y)
Cl: 0.60 = 35y/ (23x + 35y)
The values of x and y from the equation are,
x = 1 and y = 1
Thus, the answer is that the empirical formula is NaCl.