Ar(H) = 1; Ar(S) = 32; Ar(O) = 16; Mr(H₂SO₄) = (1 × 2) + 32 + (16 × 4) = 2 + 32 + 64 = 98.
Ar(H) = 1; Ar(P) = 31; Ar(O) = 16; Mr(H3РО₄) = (1 × 3) + 31 + (16 × 4) = 3 + 31 + 64 = 98.
Ar(Cu) = 64; Ar(O) = 16; Ar(H) = 1; Mr(Си(ОН)2) = 64 + (16 + 1) × 2 = 64 + 17 × 2 = 64 + 34 = 98.