Question

4. [20pt] The equilibrium constant of the reaction 2 C3H6 = C2H4 + C4H8 has been measured over a range of temperatures. Between 300 K and 600 K, it fits to the expression (T in Kelvin), 1088 1.51 · 105 In K = -1.04 - T + 12 Use this information and the Gibbs-Helmholtz equation and calculate the standard reaction enthalpy and standard reaction entropy at 400 K. /T) / (Here, the Gibbs-Helmholtz equation can be derived by taking (/ d by taking (acc/"}^(1/6)), of O /al 1/1) G = H – TS.)

Answer 1

By applying the following theorem

lnK = A + (B/T) + (C/T)² = -1.04 - (1088/400) + [1.51* 10⁵/ (400)²]

= -1.04 - 2.72 + 94.375

= 90.615

So, G°_rxn = - (8.3145 J/mol.K)(400K)(90.615) = 301349.244 KJ/mol

H°_rxn = - R[B + 2 C/T]

= - (8.3145 J/mol. K) [1088 K + 2(1.51 X 10⁵ )/400 K

= - 2.769 KJ/mol

Finally $\Delta$ S°_rxn = $\Delta$ H°_rxn - $\Delta$ G°_rxn

= -(2796 - 301349.244)/400

= - 760.36311 J/mol.K