Consider the following reatiction between oxides of nitrogen: NO 2 (g) + N 2 O(g

Question

Consider the following reatiction between oxides of nitrogen:

NO2(g) + N2O(g)   3NO(g)

Thermodynamis Quantities

210.62

(a) Use the data in the table above to predict how G° for the reaction varies with increasing tempurature.

(b) Calculate G° for the reaction at 800 K, assuming that H° and S° do not change with temperature. What is the value? Under the standard conditions is the reaction spontaneous at 800K?

(c) Calculate the G° for the reaction at 1000K. What is the value? Is the reation spontanceous inder the standard conditions at this temperature?

210.62

Explanation / Answer

a) DG = DH - T*DS

   DH > DS and as the temperature increases DS value become more large

here

if DS value is smaller than DH value so you will get +ve DG that means it is a nonspontaneous reaction.

if DS value is greater than DH value so you will get -ve DG that means it is a spontaneous reaction.

b) DG0 = [(3*90.37)-(33.84+81.6)] -800* [( 3*0.2106) -(0.24045+0.22)]

     DG0 = 18.59 Kj/mol*K

reaction is non spontaneous because DG is having +ve value

C) DG0 = [(3*90.37)-(33.84+81.6)] -1000* [( 3*0.2106) -(0.24045+0.22)]

DG0 = - 15.68 Kj/mol*K

reaction is spontaneous because DG is having -ve value

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