Question

Part B

At 25 ?C the reaction from Part A has a composition as shown in the table below.

Substance/Pressure (atM):

C2H2(g) / 4.05

H2(g) / 5.55

C2H6(g) / 5.25×10?2

What is the free energy change, ?G, in kilojoules for the reaction under these conditions? Express your answer numerically in kilojoules.

Answer 1

C₂H₂ + 2H₂                              C₂H₆

Reaction quotient, Q = P(C₂H₆) / P(C₂H₂) (PH₂)²

Here,

P(C₂H₆) = 5.25 x 10^-2

P(C₂H₂) = 4.05

(PH₂) = 5.55

Q = (5.25 x 10^-2)/ [(4.05) (5.55)²] = 4.208 x 10^-4

We have, G = G^o + RT lnQ

For the hydrogenation of acetylene, ?G^o = -242.1 KJ

G   = -241200 + 8.314 x 298 x ln (4.208 x 10^-4) = -260.459 KJ

G = -260.459 KJ