Mr(NaNO3) = Mr = Ar(Na) + Ar(N) + 3Ar(O) = 23 + 14 + 3 * 16 = 85
w(Na) = Ar(Na) / Mr = 23 / 85 = 0.27
w(N) = Ar(N) / Mr = 14 / 85 = 0.16
w(O) = 3Ar(O) / Mr = (3 * 16) / 85 = 0.57
Mr(NaNO3) = Mr = Ar(Na) + Ar(N) + 3Ar(O) = 23 + 14 + 3 * 16 = 85
w(Na) = Ar(Na) / Mr = 23 / 85 = 0.27
w(N) = Ar(N) / Mr = 14 / 85 = 0.16
w(O) = 3Ar(O) / Mr = (3 * 16) / 85 = 0.57