a) \( n = \frac{N}{N_A} = \frac{1.806 \cdot 10^{23}}{6.022 \cdot 10^{23}} = 0.3 \text{ моль} \); b) \( n = \frac{1.204 \cdot 10^{24}}{6.022 \cdot 10^{23}} = 2 \text{ моль} \); в) \( n = \frac{m}{M} = \frac{12.8}{64} = 0.2 \text{ моль} \); г) \( n = \frac{6.02 \cdot 10^{22}}{6.022 \cdot 10^{23}} = 0.1 \text{ моль} \); д) \( n = \frac{3.6 \cdot 10^{24} / 2}{6.022 \cdot 10^{23}} = 3 \text{ моль} \).