NaCl->Na->NaOH->Na2Co3->Na2SO4->NaCl

Question

NaCl->Na->NaOH->Na2Co3->Na2SO4->NaCl

Answer 1

2NaCl(электролиз расплава) = 2Na + Cl2 
2Na + 2H2O = 2NaOH + H2
2NaOH + H2CO3 = Na2CO3 + 2H2O
Na2CO3 + H2SO4 = Na2SO4 + H2O + CO2
 Na2SO4 + BaCl2 = 2NaCl + BaSO4