Question

8) Consider the following chemical reaction which is used to produce sulfur trioxide, a precursor in the industrial production of sulfuric acid: 2 SO2(g) + O2(g) → 2 50:(8) Important thermodynamic data associated with this reaction is listed in the table below. Molecule A Hº (kJ/mol) 0 -296.1 -395.2 Sº 0/K mol) 205.0 248.5 256.2 A Gº (kJ/mol) 0 -300.1 -370.4 SO (9) SOS (9) a) Calculate the equilibrium constant (K) for the above reaction at 25 °C. 6 pts) b) Calculate Ko at 60 °C. State any assumptions you used. (10 pts) c) The experimentally determined equilibrium constant for the above reaction at 60 °C is approximately 5.62 x 10". Compare this with the value you determined in part b and explain any discrepancies. (4 pts)

Answer 1

Relation b/w DG and equilibrium constant: DG= AG + RT enkeq. At equilibrium conditions ; DG=0 then, DG = - RT lu Keq. Ra Gas constant T Temperature DG & change in Gibbes free energy in standard DGY) state conditions. In non- standard State for the reaction ܠܢ 2503 (9) reactant 2.502 9.4 Oz (9) DG for reaction, Dention E AG product -EDG Allrxn. = (2x+370.4)– 2x4-300,1)+ D Girone = -140.8 + 600,2 - 140.6 kJ molt Now RT enkeq Doireaction enken 140.6 kJmolt R.T

140600 J KN enkeq. - molt In. Keqi 8.314 IK"molt x 298 k 56.74 23 43.84 x 10 At 25 c kee At 60°C, ie 333 Kelvin; le keq. 50.78 1406oo 8-314% 333 21 11.31% tó Keq. 11.31x102 With increase in temperature, the value of equilibriсm constant constant decrease. This happens when reaction in exothermic in Nature: The given reaction in Exothermic. You can verify by given values. AH, reaction = (2x –395.2) (2x -2961 products Reactants -790.4 +592.2 =-198.2 kJ molt - Heat Released The value of Keq. at 60° may vary (experimental & • Negative sign. calculated) due to maintaine Therefore, Exothermic of temperature or lack of due to ather Laboratory conditions, ie. (Experimental Errors)
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