Based on the reaction for the removal of SO_{2}, and the given data values of ΔG°_{f} and ΔH°_{f} for reactants and products, we’re asked to **determine K _{p}** of the reaction at a temperature of 298 K.

Remember that K_{p} is the Equilibrium constant in terms of pressure.

Additionally, K_{p} is related to the standard Gibbs free energy (ΔG°_{rxn}) by the following equation:

Where

ΔG°_{rxn} is the Gibbs energy of the reaction

R is the gas constant (R = 8.314 J/molK)

T is the temperature (in K)

K_{p} is the equilibrium constant in terms of pressure.

The reaction

SO_{2}(g) + 2H_{2}S(g) ⇌ 3 S(s) + 2H _{2}O(g)

is the basis of a suggested method for removal of SO _{2}, a pollutant that irritates airways causing coughing, from power-plant stack gases. The values below may be helpful when answering questions about the process.

Calculate the equilibrium constant *K*p for the reaction at a temperature of 298 K. Express the equilibrium constant to one significant figure.

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