\(n_{H_2}=\dfrac{5.6}{22.4}=0.25\left(mol\right)\)
\(Ba+2HCl\rightarrow BaCl_2+H_2\)
\(0.25................................0.25\)
\(m_{Ba}=0.25\cdot137=34.25\left(g\right)\)
$Ba+2HCl\to BaCl_2+H_2\uparrow$
$n_{H_2}=\dfrac{5,6}{22,4}=0,25(mol)$
Theo PT: $n_{Ba}=n_{H_2}=0,25(mol)$
$\Rightarrow m_{Ba}=0,25.137=34,25(g)$
$\to A$