Ответ:

4 Li + O2 -> 2 Li2O

2 Mg + O2 -> 2 MgO

4 P + 5 O2 -> 2 P2O5

Задача

Mr(H2SO4) = 1*2 + 32 + 16*4 = 98

W(H) = Ar(H) * n / Mr(H2SO4)  *100% = 1 * 2 / 98  *100% = 2%

W(S) = Ar(S) * n / Mr(H2SO4)  *100% = 32 *1 / 98  *100% =33%

W(O) = Ar(O) * n / Mr(H2SO4)  *100% = 16*4/ 98  *100% = 65%

Объяснение: