Đáp án:
`A + 2HCl -> ACl_2 + H_2`
`n_{H_2} = (4,48)/(22,4) = 0,2` `mol`
`n_A = n_{H_2} = 0,2` `mol`
`M_A = (13)/(0,2) = 65` $\text{(gam/mol)}$
$\text{Vậy A là kẽm ( Zn )}$
`Zn + 2HCl -> ZnCl_2 + H_2`
`n_{HCl} = 2n_{H_2} = 0,2 . 2 = 0,4` `mol`
`m_{HCl} = 0,4 . 36,5 = 14,6` `gam`
`C%_{HCl} = (14,6)/(500) . 100% = 2,92%`