C8
nH2S= 0.15(mol)
H2S + 2NaOH --> Na2S + 2H2O
0.15.....0.3
=> VddNaOH= 0.3/0.5= 0.6(l)
C9 nH2S= 0.05, nNaOH= 0.08(mol)
NaOH + H2S --> NaHS + H2O
a...........a...................a
2NaOH + H2S --> Na2S + 2H2O
2b................b
=> nH2S= a + b= 0.05
nNaOH= a + 2b= 0.08
=> a= 0.02, b= 0.03(mol)
=> CM(NaHS)= 0.02/0.4=0.05M
C10
nPbS= 0.01(mol) => nH2S= 0.01 => nFeS= 0.01
nH2= 0.03(mol) => nFe= 0.03
=> m= 2.56(g)