Mg3N2 + 6H2O = 3Mg(OH)2↓ + 2NH3↑;3CuO + 2NH3 = 3Cu↓ + N2↑ + 3H2O↑;m(O) = 6г;n(О) = 6 / 16 = 0.375моль;n(H2O) = n(O) = 0.375моль;n(NH3) = 0.375 * 2 / 3 = 0.25моль;n(Mg3N2) = n(NH3) / 2 = 0.125моль;m(Mg3N2) = n * M = 0.125 * (24 * 3 + 14 * 2) = 12.5гm(MgO) = 20 – 12.5 = 7.5гw(Mg3N2) = m(Mg3N2) / m(смеси) = 12.5 / 20 = 0.625; 0.625 = 62.5%w(MgО) = m(MgО) / m(смеси) = 7.5 / 20 = 0.375; 0.375 = 37,5%Ответ: 62,5%, 37,5%.