If 0.5 mole of sulfur dioxide is mixed with 0.5 mol of oxygen,then how many moles of sulfur trioxide can be obtained

Dear Student,

$2S{O}_2 + O_2 \to 2S{O}_3$
1 mole O₂ reacts with 2 mole of SO₂, so, 0.5 mole O₂ reacts with 1 mole SO₂.
Therefore, SO₂ is limiting reagent. As per given equation, 2 mole SO₂ forms 2 mole SO₃, hence 0.5 mole SO₂ will form 0.5 mole of SO₃.
Regards