a,
$Fe+S\buildrel{{t^o}}\over\to FeS$
$Fe+2HCl\to FeCl_2+H_2$
$FeS+2HCl\to FeCl_2+H_2S$
$Pb(NO_3)_2+H_2S\to PbS+2HNO_3$
$A: Fe, FeS$
$B: H_2, H_2S$
$D: PbS$
b,
$n_{Fe}=\dfrac{16,8}{56}=0,3(mol)$
$n_S=\dfrac{6,4}{32}=0,2(mol)$
$\Rightarrow Fe$ dư
$n_{FeS}=n_S=0,2(mol)$
$\Rightarrow n_{H_2S}=n_{FeS}=0,2(mol)$
$n_{Fe\text{dư}}=0,3-0,2=0,1(mol)$
$\Rightarrow n_{H_2}=n_{Fe}=0,1(mol)$
$\to V_B=22,4(0,1+0,2)=0,3.22,4=6,72l$
$n_{PbS}=n_{H_2S}=0,2(mol)$
$\to m_{D\downarrow}=0,2.239=47,8g$
c,
$H_2S+1,5O_2\buildrel{{t^o}}\over\to SO_2+H_2O$
$H_2+0,5O_2\buildrel{{t^o}}\over\to H_2O$
$n_{O_2}=0,2.1,5+0,1.0,5=0,35(mol)$
$\to V_{O_2}=0,35.22,4=7,84l$