Use the standard enthalpies and entropies of formation in the table below to ans

Question

Use the standard enthalpies and entropies of formation in the table below to answer the following questions. Hfº (kJ/mol) Sfº (J/K/mol) H2O2(l) -187.8 109.6 H2O(l) -285.8 70.0 C2H4(g) 52.4 219.3 C2H4O(l) -78.0 153.9

a) What is the standard change in the Gibbs Free Energy for the following reaction: H2O2(l) + C2H4(g) --> H2O(l) + C2H4O(l)?

b) At what temperatures will the reaction in part a be spontaneous?

c) What is the equilibrium constant for the reaction in part a under standard conditions? (10 pts)

Explanation / Answer

H2O2(l) + C2H4(g) --> H2O(l) + C2H4O(l)

DH0rxn = (-78+-285.8)-(-187.8+52.4) = - 228.4 kj

DS0rxn = (153.9+70)-(109.6+219.3) = -105 j/mol.k

DG0 = DH0-TDS0

for a process to be spontaneous,DG = 0 (or) lessthan 0.

   0 = (-228.4)-(T*-105*10^-3)

T = 2175.24 k

at , T = 2175.24 k it is spontaneous.

b) at standard conditions , T = 298 k

DG0 = (-228.4)-(298*-105*10^-3)

     = -197.11 kj/mol

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