Question

Consider the following reaction: 2 NO(g) + Cl2(g) = 2 NOCI() The reaction is at equilibrium at 125 °C with PNo = 1.66 bar, PcI2 = 0.830 bar, and PNoci = 1.09 bar. (a) Calculate the value of the equilibrium constant of this reaction at 125 °C. (b) Calculate the value of AGº of this reaction at 125 °C. Give you answer with 3 significant figures and in the units kJ/mol. (c) Given the following additional information and assuming that AH° is independent of temperature, calculate the value of the equilibrium constant of this reaction at 635 °C. Give your answer with 3 significant figures. At 25 °C, AHºfof NO(g) = 91.3 kJ/mol and AHºfof NOCI(g) = 51.7 kJ/mol

Answer 1

The giren reaction is - 2 NO CG) + cl₂ (9) 7 2 Noch (9) The equilibrium constant (kp) is given by - Kp = (Proci Po= standerd atmospheric Pressure 2 (Pwo/p) (Parloo) - 1 bar la) we have given PNO -1.66 bar P = 0.830 tar Prode= 1.09 bar (1.09 bar, ar/1 bar) ke for this reaction & xp = ( 16Gbory, bary 10.8506) 0.518 kp at 125°c is .0.519 (O) we know that, 6= - RT ln Kp (8.314 J K 'mo1') (398k) h0.619 The temperature of the system is 125°C = 3986 .cho =2170.194 J more og for the reaction is 2.170 kJ/mol (1) The enthalpy of the reaction is given by OH OHf products Ei reactants so is the stoichio metry of the Products reactants, Gut = {(2x51.7) - (ex 91.3) + (1x 0)} - 79.2 KJ (otty of cha=0) A 11

we know that temperature dependence of kp is given by van't Hoff equation- d lukp RT if we integrate the equation within limits of T, and Ta In (Kp2 G-4) arto R 3 Now we have, Ti = 125°c = 398k kp- Ayyy 0.519 T2 = 635c - 9o8k tp = ? Ost = 2150 J/mol 2170/mot 908k 3986 In Ker 0.519. 8.314 of mot x- = -261 (-1.41X10-3) 0.368 KP.2 en 0.38.8 - 0.519 Rp2 = 1:45 0.549 Kp2 - J: 45 x 0.594 = 0.750, 0.750 Kp at 635°c