Sample Problem 20.6
PROBLEM:
PLAN:
SOLUTION:
Determining the effect of temperature on DGo
An important reaction in the production of sulfuric acid is the oxidation of SO2(g) to SO3(g):
At 298 K, DGo = -141.6 kJ, DHo = -198.4 kJ, and DSo = -187.9 J/K.
(a) Use these data to decide if this reaction is spontaneous at 25 oC, and predict how DGo will change with increasing T.
(b) Assuming DHo and DSo are constant with increasing T, is the reaction spontaneous at 900. oC?
The sign of DGo tells us whether the reaction is spontaneous and the signs of DHo and DSo will be indicative of the T effect. Use the Gibbs free energy equation for part (b).
(a) The reaction is spontaneous at 25 oC because DGo is (-). Since DHo is (-) and DSo is (-), DGo will become less negative and the reaction less spontaneous as temperature increases.
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