0.25 mols SO₂ x 64.058 g SO₂/ 1 mol SO₂ = 16.0145 g SO₂
molar mass of SO₂: 64.058 g
answer: 16 grams of SO₂ (2 sig figs)
check the question to see if its asked for a specific unit for mass (grams or kilograms, if they asked for kiligrams then convert 16 grams to kilograms by dividing it by 1000)