\(1/\\ Tổng: 2p+n=49(1)\\ \text{Hạt không mang điện bằng 53,125% số hạt mang điện: }\\ n=2.53,125\%p\\ \to -1,0625p-n=0(2)\\ (1)(2)\\ p=e=16\\ n=17\\ A=16+17=33 (S)\\ \)

\(CO_2+2NaOH \to Na_2CO_3+H_2O\\ n_{CO_2}=0,05(mol)\\ a/\\ n_{NaOH}=0,05.2=0,1(mol)\\ CM_{NaOH}=\frac{0,1}{0,1}=1M\\ b/\\ n_{Na_2CO_3}=n_{CO_2}=0,05(mol)\\ m_{Na_2CO_3}=0,05.106=5,3(g)\)

\(m_{Khan}=0,04.27+0,07.96+0,01.24=8,04(g)\\ \to B\)

\(\text{Chọn B}\\ \text{Gồm: (3); (5);(6)}\)

\(\text{Giả sử có 1 mol MO: }\\ MO+H_2SO_4 \to MSO_4+H_2O\\ m_{ddH_2SO_4}=\frac{98.100}{20}=490(g)\\ C\%_{MSO_4}=\frac{M+96}{M+16+490}.100\%=22,64\%\\ \to M=24(Mg)\\ \to MgO\)

\([H^{+}]=0,004+0,0008.2=0,0056M\\ pH=-log(0,0056)=2,25\)

\(\begin{cases} 2p+n=34 (1)\\ 2p-n=10 (2) \end{cases} \to \begin{cases} p=e=11 \\ n=12 \end{cases}\)

\(n_{Fe_2O_3}=0,2(mol)\\ Fe_2O_3+6HCl \to 2FeCl_3+3H_2O\\ n_{HCl}=1,2(mol)\\ V_{ddHCl}=\frac{250}{1,25}=200(ml)=0,2(l)\\ CM_{HCl}=\frac{1,2}{0,2}=6M$\)

\(NaOH+HCl \to NaCl+H_2O\\ n_{NaOH}=0,06(mol)\\ \to n_{HCl}=0,06(mol)\\ V_{HCl}=\frac{0,06}{0,6}=0,1(l)=100(ml)\)

\(Tổng: 2p+n=155 (1)\\ MĐ > KMĐ: 2p-n=33(2)\\ (1)(2)\\ p=e=47\\ n=61\\ A=47+61=108 (Ag)\)