Question
(a) What are Exergonic and Endergonic reactions?
(b) Given that the standard heat of formation of NH3(g) as represented by the equation
is – 46.191 kJ. The standard entropies of N2(g), H2(g) and NH3(g) are 191.62, 130.12 and 193.3 JK–1 mol–1 respectively. Calculate the standard free energy of formation (∆G0) for NH3. Is the reaction feasible?
Solution
(a) A reaction which is accompanied by the decrease of free energy is called exergonic reaction. All spontaneous processes are exergonic. It means in an exoergic reaction, ∆G is less than zero i.e. ∆G is negative.
A reaction Which is accompanied by the increase of free energy is called endergonic reaction. All non-spontaneous processes are endergonic. It means an endergonic reaction ∆G is greater than zero i.e. ∆G is positive.
(b) Here,
We know,
Also,
Substituting the values, we have,
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Since the value of ∆rG° is negative, the reaction is feasible.
A reaction Which is accompanied by the increase of free energy is called endergonic reaction. All non-spontaneous processes are endergonic. It means an endergonic reaction ∆G is greater than zero i.e. ∆G is positive.
(b) Here,
We know,
Also,
Substituting the values, we have,
Since the value of ∆rG° is negative, the reaction is feasible.
