m d d H 2 S O 4 = 98 ( g ) mddH2SO4=98(g) m H 2 S O 4 = 98 ⋅ 20 % = 19.6 ( g ) mH2SO4=98⋅20%=19.6(g) n H 2 S O 4 = 19.6 98 = 0.2 ( m o l ) nH2SO4=19.698=0.2(mol) M O + H 2 S O 4 → M S O 4 + H 2 O MO+H2SO4→MSO4+H2O 0.2........0.2...............0.2 0.2........0.2...............0.2 m M S O 4 = 0.2 ⋅ ( M + 96 ) ( g ) mMSO4=0.2⋅(M+96)(g) m d d Y = 0.2 ⋅ ( M + 16 ) + 98 = 0.2 M + 101.2 ( g ) mddY=0.2⋅(M+16)+98=0.2M+101.2(g) C % M S O 4 = 0.2 ⋅ ( M + 96 ) 0.2 M + 101.2 ⋅ 100 % = 22.64 % C%MSO4=0.2⋅(M+96)0.2M+101.2⋅100%=22.64% ⇔ M = 24 ⇔M=24 M : M g

Gọi hóa trị của AO là a.