Câu 1: A
\(Cu+2AgNO_3\rightarrow Cu\left(NO_3\right)_2+2Ag\downarrow\)
Câu 2: B
\(2Al+3ZnCl_2\rightarrow2AlCl_3+3Zn\downarrow\)
Câu 3: A
Câu 4: B
\(n_{H_2}=\dfrac{0,2}{2}=0,1\left(mol\right)\)
PTHH: \(2A+2H_2O\rightarrow2AOH+H_2\)
0,2<-------------------------0,1
=> \(M_A=\dfrac{4,6}{0,2}=23\left(g/mol\right)\)
=> A là Na
