a, NaOH + SO2 --> NaHSO3
NaOH + 2SO2 --> Na2SO3 + H2O
b, Gọi nNaHSO3=x, nNa2SO3=y
BTNT Na có nNaHSO3 + 2.nNa2SO3=nNaOH => x + 2y = 0,2
mNaHSO3 + mNa2SO3=16,7 <=> 104x + 126y = 16,7
=>x=0,1 ; y=0,05
BTNT S có: nSO2=nNaHSO3 + nNa2SO3= x+ y=0,1+0,05=0,15
=> V=0,15.22,4=3,36 lit