Do dung dịch chỉ chưa muối sunfat
FeS2------->Fe2(SO4)3
0,18 ------->0,18/2=0,09 mol
Cu2S---------------->CuSO4
a mol---------------->2a mol
Bảo toàn nguyên tố S ta có:
0,18.2+a=0,09.3+2a=>a=0,09 mol
FeS2------------->Fe(+3) + 2S(+6) + 15e
0,18-------------------------------------->0,18.15=2,7 mol
CU2S-------------------->2Cu(+2) + S(+6) +10e
0,09-------------------------------------------->0,9 MOL
N(+5) +3e------------------>NO
(2,7+0.9)--------------->1,2 mol
=>V=1,2.22,4=26,88 (l)