Для N2O5:
Mr(N2O5) = 2 × 14 + 5 × 16 = 28 + 80 = 108
ω(N) = (2 × 14) / 108 = 28 / 108 ≈ 0.2593, или 25.93%
ω(O) = (5 × 16) / 108 = 80 / 108 ≈ 0.7407, или 74.07%