Sample Problem 20.3
SOLUTION:
Determining reaction spontaneity
Calculate DSouniv and state whether the reaction occurs spontaneously at this temperature.
DHorxn = [(2 mol)(DHof NH3)] - [(1 mol)(DHof N2) + (3 mol)(DHof H2)]
DHorxn = -91.8 kJ
DSosurr = -DHosys/T =
-(-91.8 x 103J/298 K)
= +308 J/K (>+197 J/K)
DSouniv = DSosurr + DSosys
= 308 J/K + (-197 J/K) = +111 J/K
DSouniv > 0: the reaction is spontaneous!
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