Question

Sulfuric acid is produced in larger amounts by weight than any other chemical. It is used in manufacturing fertilizers, oil refining, and hundreds of other processes. An intermediate step in the industrial process for the synthesis of H2SO4 is the catalytic oxidation of sulfur dioxide:
2SO2(g)+O2(g)→2SO3(g)ΔG∘ = -141.8 kJ
Calculate ΔG at 25 ∘C given the following sets of partial pressures.

Part A

150 atm SO2, 150 atm O2, 4.0 atm SO3

Express your answer using four significant figures.

Part B

4.0 atm SO2, 1.0 atm O2, 10 atm SO3

Express your answer using four significant figures.

Part C

Each reactant and product at a partial pressure of 1.0 atm.

Express your answer using four significant figures.

Answer 1

2SO2(g)+O2(g)?2SO3(g)?G? = -141.8 kJ

?G? = -141.8 kJ   = -141800J

Part A

150 atm SO2, 150 atm O2, 4.0 atm SO3

KP   = P² SO3/P²SO2 PO2

       = (4)^2/(150)^2 *150   = 4.74*10^-6

?G   = ?G⁰ + RTlnKp

       = -141800+ 8.314*298ln4.74*10^-6

      = -141800+ 8.314*298*-12.2594    = -172173.55J    = -172.2KJ

Part B

4.0 atm SO2, 1.0 atm O2, 10 atm SO3

KP   = P² SO3/P²SO2 PO2

       = (10)^2/(4)^2 *1 = 6.25

?G   = ?G⁰ + RTlnKp

       = -141800+ 8.314*298ln6.25

        = -141800+8.314*298*1.8325

         = -137259.85J     = -137.3KJ

Part C

Each reactant and product at a partial pressure of 1.0 atm.

KP   = P² SO3/P²SO2 PO2

        = (1)^2/(1)^2 *1   = 1

?G   = ?G⁰ + RTlnKp

       = -141800+ 8.314*298ln1

        = -141800+8.314*298*0

        = -141800J   = 141.8KJ