Write the reaction equations: SO3 → H2SO4 → K2SO4 → BaSO4

To carry out the above chain of transformations, the following reactions must be performed:
Sulfur and oxygen, as a result of the reaction, produces tetravalent sulfur oxide.
S + O2 = SO2
Oxygen is added to tetravalent sulfur oxide, as a result of the reaction we obtain hexavalent sulfur oxide.
2 SO2 + O2 = 2 SO3
We add water to hexavalent sulfur oxide, we get sulfuric acid.
H2O + SO3 = H2SO4
We add potassium hydroxide to sulfuric acid, as a result of the reaction we get potassium sulfate and water.
2 KOH + H2SO4 = K2SO4 + 2 H2O
We add barium chloride to potassium sulfate; as a result of the reaction, barium sulfate and potassium chloride are obtained.
K2SO4 + BaCl2 = BaSO4 + 2 KCl