а) Mr(CaO) = 40 + 16=56
W(Ca) = Ar(Ca) * n / Mr(CaO) *100% = 40*1 / 56 *100% = 71%
W(O) = Ar(O) * n / Mr(CaO) *100% = 16*1 / 56 *100% = 29%
б) Mr(MgS) = 24+32 = 56
W(Mg) = Ar(Mg)*n / Mr(MgS) * 100% = 24*1 / 56 *100% = 43%
W(S) = Ar(S) * n / Mr(MgS) *100% = 32*1 / 56 *100% = 57%