H2SO3 + Na2SO3 + NaCl + Na2SO4 → Na2SO3 + NaCl + Na2SO4 + H2SO3 In this reaction, H2SO3 reacts with Na2SO3 to form Na2S2O5 and H2O: H2SO3 + Na2SO3 → Na2S2O5 + H2O Then, Na2S2O5 reacts with Na2SO3 to form Na2S4O6: Na2S2O5 + Na2SO3 → Na2S4O6 + SO2 Next, Na2S4O6 reacts with NaCl to form Na2S2O3, Na2SO4, and Cl2: Na2S4O6 + 2NaCl → 2Na2S2O3 + Na2SO4 + Cl2 Finally, Na2S2O3 reacts with Na2SO4 to form Na2S2O7 and Na2SO3: Na2S2O3 + Na2SO4 → Na2S2O7 + Na2SO3 The overall reaction can be written as: H2SO3 + Na2SO3 + NaCl + Na2SO4 → Na2S2O7 + SO2 + H2O + 2Na2SO3 + Cl2