2. Mr (Al(OH)3) = Ar(Al) + 3 × Ar(O) + 3 × Ar(H).Ar(Al) = 27, Ar(O) = 16, Ar(H) = 1.Mr (Al(OH)3) = 27 + 3 × 16 + 3 × 1 = 27 + 48 + 3 = 78.
Ответ: 78