The second step of the Contact process for producing sulfuric acid involves the…
CHEMISTRY · Multi-part · A Level · Chemistry · Chemical equilibria (Le Chatelier’s principle and Kc) · Chemical equilibria (Le Chatelier’s principle and Kc)
Problem
The second step of the Contact process for producing sulfuric acid involves the equilibrium
2 SO₂(g) + O₂(g) ⇌ 2 SO₃(g) ΔH∘=−197kJ mol−1
At 700 K, the equilibrium constant expressed in terms of concentration is Kc=3.0. A mixture containing 0.200 mol SO₂ and 0.120 mol O₂ is introduced into an evacuated 5.00 L reactor at 700 K.
Answer the following questions about this industrial system.
(1) Part 1: (a) Calculate the equilibrium concentration (in mol L⁻¹) of SO₃ at 700 K for the initial mixture described.
(2) Part 2: (b) The reactor temperature is lowered to 650 K, at which Kc=12. Qualitatively describe how the equilibrium concentrations of SO₂, O₂, and SO₃ will change as the system adjusts to the new temperature. No numerical calculation is required.
(3) Part 3: (c) Continuous operation of the plant removes SO₃ as it forms and recycles unreacted gases. If one pass through the reactor converts 60 % of the entering SO₂ to SO₃, calculate the fraction of the original SO₂ feed that remains unconverted after two consecutive passes (assume identical performance in each pass and perfect separation of SO₃ between passes).
(4) Part 4: (d) Discuss one operational advantage and one potential drawback of lowering the reactor temperature to increase SO₃ yield in the Contact process.