Question

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

Substance	Pressure (atm)
C2H2(g)	4.15
H2(g)	4.25
C2H6(g)	4.25×10−2

What is the free energy change, ΔG, in kilojoules for the reaction under these conditions?

Express your answer numerically in kilojoules.

Answer 1

We find   Q of reaction , Q means reaction quotient

C2H2 + 2H2 -----------------> C2H6

4.15     4.25                          4.25 x 10^-2

Qp = P_C2H6 / P_C2H2 P_H2²

      = 4.25 x 10^-2 / (4.15) (4.25)^2

       = 5.67 x 10^-4

R = 8.314 x 10^-3 kJ/ K mol

T = 273 + 25 = 298 K

G   = Go + RT lnQp

G   = Go + 2.303 RT log Qp

        = -242.1 + 2.303 x 8.314 x 10^-3 x 298 x log (5.67 x 10^-4)

        = -260.6 kJ

G = -260.6 kJ