Consider the decomposition of the compound C3H6O3 asfollows: C5H6O3(g)---> C2H6(g) + 3CO(g) When a 5.63 g sample of pure C5H6O3(g) was sealed into anotherwise empty 2.50 L flask and heated to 200 degrees C thepressure in the flask gradually rose to 1.63 atm and remained atthat value. Calculate K for this reaction. Consider the decomposition of the compound C3H6O3 asfollows: C5H6O3(g)---> C2H6(g) + 3CO(g) When a 5.63 g sample of pure C5H6O3(g) was sealed into anotherwise empty 2.50 L flask and heated to 200 degrees C thepressure in the flask gradually rose to 1.63 atm and remained atthat value. Calculate K for this reaction.
Explanation / Answer
Mass = 5.63 g Moles = Mass / molar mass =5.63 g/ 180.19 g/mol =0.0312 moles Volume = 2.50 L T= 200 C = 473 K Initial pressure, P = nRT / V =0.0312 * 0.0821 L-atm/ mol. K * 473 / 2.50L =0.485 atm C5H6O3(g)--->C2H6(g) + 3CO(g) Initial 0.485 0 0 Change -x +x +3x Equilibrium (0.485-x) x 3 x At equilibrium, total pressure = 1.63 atm = (0.485 - x ) + x +3x So x = 0.382 So at equilibrium, p[C5H6O3] = 0.485- 0.382 = 0.103 atm p [ C2H6] = 0.382 atm p[CO] = 3 (0.382) = 1.146 atm K = [pC2H6] [ p CO] 3 / p[C5H6O3] = 0.382 atm * (1.146)3 /0.103 atm = 5.58