I.

2 NO(g) + 0 2(g)-> 2 N02(g) , L1,SO = -146.5 J/K The reaction represented above is one that contributes significantly to the formation of photochemical smog.

(a) Calculate the quantity of heat released when 73.1 g ofNO(g) is converted to N02(g).

(b) For the reaction at 25C, the value of the standard free-energy change, LIG0 , is -70.4 kJ.

(i) Calculate the value of the equilibrium constant, K.q, for the reaction at 25C.

(ii) Indicate whether the value of LIG0 would become more negative, less negative, or remain unchanged as the temperature is increased. Justify your answer.

(c) Use the data in the table below to calculate the value of the standard entropy, S0 , for 0 2(g) at 25C.

Standard Molar Entropy, so (J/mol K)

NO(g) 210.8

N02(g) 240.1

(d) Use the data in the table below to calculate the bond energy, in kJ/mol of the nitrogen-oxygen bond in N02(g). Assume that the bonds in the N02(g) molecule are equivalent (i.e. , they have the same energy).

Bond Energy (kJ/mol)

Nitrogen-oxygen bond in NO 607

Oxygen-oxygen bond in 0 2 495

Nitrogen-oxygen bond in N02 ?

L\W = +95.4 kJ mor'; L\S0 = -176 J K-1 mor'

2. Answer the following questions about the reaction represented above using principles of thermodynamics.

(a)

(b)

(c)

On the basis of the thermodynamic data given above, compare the sum of the bond strengths of the reactants to the sum of the bond strengths ofthe product. Justify your answer.

Does the entropy change of the n;actiQP favor the reactants or the product? Justify your answer.

For the reaction under the condianswer.

(d) Explain how to determine the value of the equilibrium constant, Keg , for the reaction. (Do not do any calculations.)

(e) Predict whether the value ofKeq for the reaction lis greater than I, equal to I, or less than I. Justify your answer.