$n_{Na}=0,1(mol);n_{Zn}=0,1(mol)$
$2Na+S\xrightarrow{t^o}Na_2S$
$Zn+S\xrightarrow{t^o}ZnS$
$Na_2S+2HCl\to 2NaCl+H_2S$
$ZnS+2HCl\to ZnCl_2+H_2S$
Theo PT: $\sum n_{H_2S}=\frac{1}{2}n_{Na}+n_{Zn}=0,15(mol)$
$H_2S+Cu(NO_3)_2\to CuS\downarrow+2HNO_3$
Theo PT: $n_{CuS}=n_{H_2S}=0,15(mol)$
$\to a=0,15.96=14,4(g)$