The values of heat of formation of SO₂ and SO₃ are -298.2 kJ and -98.2 kJ. The heat of formation of this reaction will be SO₂ + (1/2)O₂ → SO₃

Options

(a) 200 kJ
(b) -356.2 kJ
(c) -200 kJ
(d) -396.2 kJ

Correct Answer:

200 kJ

Explanation:

Values of heat formation of SO₂ = -298.2 kJ and that of SO₃ = -98.2 kJ.
Therefore S(s) + O₂(g) → SO₂(g) , ΔH = -298.2 kJ ..(i)
and S(s) + (3/2)O₂(g) → SO₃(g), ΔH = -98.2 kJ ..(ii)
Subtracting equation, (i) from (ii), we get,
SO₂ + 1/2O₂ → SO₃. ΔH = -98.2 – (-298.2) = 200 kJ.