Question

Calcium Oxide is used to remove pollutant SO2 from smokestack gases. The ΔG° of the overall reaction is -418.6 kJ. What is PSO2 in equilibrium with air (PO2 = 0.21 atm) and solid CaO?
CaO(s)+SO2 (g)+1⁄2O2 (g)⇔CaSO4 (s)

Answer 1

From the change in free energy, we can calculate the equilibrium constant by the equation ΔG°=-RT ln(K) where K is the equilibrium constant.

-418.6x10^2 = -(8.314)(298) ln (K)
K = 2.38x10^73

K is expressed as:

K = 1 / Pso2 (Po2)^0.5 = 1/ Pso2 (0.21)^0.5
 2.38x10^73 = 1/ Pso2 (0.21)^0.5
Pso2 = 9.17x10^-74 atm