Question

Consider the following gas-phase reaction: C6H6(g) 3 C2H2(g) Using data from Appendix C of your textbook calculate the temperature, To, at which this reaction will be at equilibrium under standard conditions (Go = 0) and choose whether >Go will increase, decrease, or not change with increasing temperature from the pulldown menu.

T = ____K, and G will _______

For each of the temperatures listed below calculate G for the reaction above, and select from the pulldown menu whether the reaction under standard conditions will be spontaneous, nonspontaneous, or near equilibrium ("near equilibrium" means that T is within 5 K of To).

(a) At T = 896 K G=

(b) At T = 1792 K G=

(c) At T = 2688 K G=

Answer 1

C6H6(g)--------------> 3 C2H2(g)

H = Hf products - Hf reactants

       = 3*226.7 -82.9   = 597.2Kj/mole

S = Sf products - Sf reactants

        = 3*200.9 -269.2 = 333.5j/mole-K   = 0.335Kj/mole-K

G   = H-TS

         = 597.2-298*0.3335   = 497.817KJ/mole

G>0 non spontaneous reaction

(a) At T = 896 K

G   = H-TS

          = 597.2-896*0.3335   = 298.384Kj/mole

G>0 non spontaneous reaction

(b) At T = 1792 K

G   = H-TS

         = 597.2-1792*0.3335    = -0.432Kj/mole

G<0 spontaneous reaction

(c) At T = 2688 K

G   = H-TS

         = 597.2-2688*0.3335   = -299.248KJ/mole

G <0 spontaneous reaction