Statement-I : ${\text{SO}}_{\text{3}}$ Is more acidic than ${\text{SO}}_{\text{2}}$ 
Statement-II : Potassium chlorate on thermal decomposition in presence of ${\text{MnO}}_2$ Gives oxygen

According to the theories, sulfur trioxide (SO₃) should be more acidic than sulfur dioxide because sulfur trioxide reacts violently with water and forms sulfuric acid, which is a stronger acid than sulfurous acid. Therefore, SO₃ is more acidic than SO₂.

To do this, the potassium chlorate must be heated to temperatures greater than 400 °C, causing it to thermally decompose into potassium chloride and free oxygen:

 2 KClO₃ (s) →  2 KCl (s) + 3O₂ (g)