Question

5. Consider a gaseous reaction, A + 4B2C + D. It was found that when 2.00 mol A, 5.00 mol B and 2.00 mol D were mixed and allowed to come to an equilibrium at 25°C, the resulting mixture has 1.60 mol of C at the total pressure of 2.00 atm. The standard reaction enthalpy for this process is A Hº = -90.0 kJ/mol. (a) [8 points) Calculate the equilibrium constants, Km, and K. (b) (7 points) Calculate the standard Gibbs free energy change (4,6°) for this reaction. What will be the equilibrium constant (K) for this process if the temperature is raised from 25 to 50°C? (c) (5 points) What will happen (increase or decrease) to the mole fraction of species D if the pressure is raised to 4.00 atm? Justify your answer using Le Chatelier's principle to get a credit.

Answer 1

A (g) + 4B (g) 2 C(q) + D (g) . At t=0 a mole smole e amole At t= teq 2-4 5-40 au 2+k moles of " Melt tege Given : Kg 4 in the resulting mixhere) = 1.6 mote e ze (n=0.8%. 22 -0,8=1.2 mol Alt= teq nel B rito -5-4X0,8=5-3.2=1.8 mole moles 2+= 2+0,8 z 2.8 Matc Mal. 'Tltater = 1, 2 +1,8 t 2,8 +1.6z 7.4 mole

Pacg) = Xp. Pp = m xfp = 1/2 x 2 atm mole fraction of A r t atm = 0.33 atm Po (9) = xo prema PpLo ? 12 et = 0.494 atm 7,4 2.4 Pc (9) = Xc Pp 346X20.432 atm Ý, (3) - *, 1 • 2.x2 = . 35k an (a) Keq = Kp = P2P = 7.663 (atm) 0.48619 x 0-3? Universal Gas censtout Ar 90 - - RT en Key = – 8314,2 X 298Kzln 7.663 Kmole (0.432) X 0.75 ArG2-5045,3361 3 A.G² = -5.0453 kJ mote I by Van't hoff equation ? ( Temperature dependency on kes in/ (kes),-) I F +2 -12 T = 25°C = 298k TP282=2104 T250'=321K. e n het gehele 7.663/ ]

2 -90x1000 (327-298 8,914 L 298 X323 17.663 , (Keel -2.812 - - e 7-663 . 0.06008 x 7.663 (atm) 0:4604 lath-2 since the reaction is enothermic , thus an increasing the temperature from 2988 to 323k, the keq decreases by Le-chatelier's principle. as temperature remains same o 91 pressure is raised to Yatm, then volume decreases this crowding increases (no of species participating at equilibrium increases). Now this increase in Crowding will create a stress on the system, reaction will go in that direction where the stress can be minunised it forward direction by Leo Chatelier's principle . So, more moles of o will get formed thes, mole fraction of I will increase .