O3(g) + NO(g) O2(g) + NO2(g) Consider the reaction represented above. a. Referri
ID: 978603 • Letter: O
Question
O3(g) + NO(g) O2(g) + NO2(g) Consider the reaction represented above. a.
Referring to the data in the table below, calculate the standard enthalpy change H, for the reaction at 25C :
Standard enthalpy of formation, Hƒ, at 25C (kJ/mol), O3(g) = 123, NO(g) = 110. NO2(g) =43
b. Make a qualitative prediction about the magnitude of the standard entropy change, S, for the reaction at 25C. Justify your answer.
c. On the basis of your answers to parts (a) and (b), predict the sign of the standard free energy change, G, for the reaction at 25C. Explain your reasoning.
Explanation / Answer
a) Given reaction is O3(g) + NO(g) --------------> O2(g) + NO2(g)
Hƒ , at 25C (kJ/mol),
O3(g) = 123
NO(g) = 110
NO2(g) = 43
We know that Hƒ of O2 (g) = 0
standard enthalpy change H = Hƒ of products - Hƒ of reactants
= Hƒ of (O2 + NO2) - Hƒ of (O3 +NO)
= 0 + 43 - ( 123 + 110)
= - 190 kJ/mol
b)
S for this reaction is near zero (or) zero becuase no of moles of gas is same on each side of the equation.
c)
We know that Go = Ho - TSo
From above, Ho = -ve , So = near zero
Hence,
Go = -ve - Tx ( near zero) = -ve
Therefore,
Go = negative.
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