Em tham khảo nha:

\(\begin{array}{l}
21)\\
{M_A} = 2 \times {M_{{O_2}}} = 2 \times 32 = 64\,dvC\\
22)\\
{M_B} = 2,207 \times {M_{kk}} = 2,207 \times 29 = 64,003\,dvC\\
23)\\
1.\,2Mg + {O_2} \xrightarrow{t^0} 2MgO\\
2.\,Fe + 2HCl \to FeC{l_2} + {H_2}\\
3.\,2Cu + {O_2} \xrightarrow{t^0} 2CuO\\
4.\,Zn + 2HCl \to ZnC{l_2} + {H_2}\\
5.\,CaO + 2HN{O_3} \to Ca{(N{O_3})_2} + {H_2}O\\
6.\,CaC{O_3} \xrightarrow{t^0} CaO + C{O_2}\\
7.\,2Al{(OH)_3} \xrightarrow{t^0} A{l_2}{O_3} + 3{H_2}O\\
8.\,Fe + 2AgN{O_3} \to Fe{(N{O_3})_2} + 2Ag\\
9.\,C{O_2} + Ca{(OH)_2} \to CaC{O_3} + {H_2}O\\
10.\,Al + 3AgN{O_3} \to Al{(N{O_3})_3} + 3Ag\\
11.\,CaC{O_3} + 2HCl \to CaC{l_2} + C{O_2} + {H_2}O\\
12.\,4Na + {O_2} \xrightarrow{t^0} 2N{a_2}O\\
13.\,2Mg + {O_2} \xrightarrow{t^0} 2MgO\\
14.4P + 5{O_2} \xrightarrow{t^0} 2{P_2}{O_5}\\
15.\,4Al + 3{O_2} \xrightarrow{t^0} 2A{l_2}{O_3}\\
16.\,3Fe + 2{O_2} \xrightarrow{t^0} F{e_3}{O_4}
\end{array}\)

Đáp án:

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