Дано
N(Al) = 12.04 * 10^23
Решение
n(Al) = N(Al) * Na = (12.04 * 10^23) / (6.02 * 10^23) = 12.04 / 6.02 = 2 моль
4Al + 3O2 = 2Al2O3
n(Al2O3) = 0.5n(Al) = 0.5 * 2 = 1 моль
m(Al2O3) = n(Al2O3)M(Al2O3) = 1 * (2 * 27 + 3 * 16) = 102 г
Ответ: Al2O3, 102 г