Answer is: The molecular mass of sodium oxide is A. 61.97894.
M(Na₂O) = 2 · Ar(Na) + Ar(O).
M(Na₂O) = 2 · 22.98976 + 15.9994.
M(Na₂O) = 61.97894; molecular mass of sodium oxide.
Ar is relative atomic mass (the ratio of the average mass of atoms of a chemical element to one unified atomic mass unit) of an element.
