In the reaction
CS2(l) + 3O2(g) → CO2(g) + 2SO2(g) ΔH = −265 kcal
The enthalpies of formation of CO2 and SO2 are both negative and are in the ratio 4 : 3. The enthalpy of formation of CS2 is +26 kcal/mol. Calculate the enthalpy of formation of SO2.
−71.7 kcal/mol
CS2(l) + 3O2(g) → CO2(g) + 2SO2(g)
ΔH = −256 Kcal
Let ΔHr(CO2,g) = −4x and ΔHr(SO2,g) = −3x
ΔHreaction = ΔHf(CO2,g) + 2ΔΔf(SO2,g) − ΔHf(CS2I)
−265 = −4x − 6x − 26
x = +23.9
∴ Δf(SO2,g) = 3x = −71.7 Kcal/mol