m (СnH2nO) = 174 g
m (Ag) = 648 g
1) СnH2nO + 2 [Ag (NH3) 2] OH => 2Ag ↓ + СnH2nO2NH4 + 3NH3 + H2O;
2) n (Ag) = m (Ag) / M (Ag) = 648/108 = 6 mol;
3) n (СnH2nO) = n (Ag) / 2 = 6/2 = 3 mol;
4) M (CnH2nO) = m (CnH2nO) / n (CnH2nO) = 174/3 = 58 g / mol;
5) M (CnH2nO) = Mr (CnH2nO) = Ar (C) * N (C) + Ar (H) * N (H) + Ar (O) * N (O);
58 = 12 * n + 1 * 2n + 16 * 1;
n = 3;
6) Unknown substance – C3H6O – propanal.
Answer: Unknown substance – C3H6O – propanal.
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