Дано:
Al₂O₃
w(Al) - ?
w(O) - ?
Ar(Al) = 27
Ar(O) = 16
Розв'язання
Mr(Al₂O₃) = 2Ar(Al) + 3Ar(O)
Mr(Al₂O₃) = 2 * 27 + 3 * 16 = 102
w(Al) = n * Ar(Al) / Mr(Al₂O₃) * 100%
w(Al) = 2 * 27 / 102 * 100% = 0.5294 або 53%
w(O) = 100% - w(Al)
w(O) = 100% - 53% = 47%
Вiдповiдь: w(Al) = 53%, w(O) = 47%