Question

he following chemical equations describe the same chemi-cal reaction. How do the free energies of these two chemical equations compare?

I KNOW THE ANSWER IS B BUT EXPLAIN YOUR REASONING!

(1) 2 H₂O (l) ---> 2 H₂ (g) + O₂(g)

(2) H₂O (l) ---> H₂ (g) + 1/2 O₂(g)

(a) ∆G°1=∆G°2

(b) ∆G°1=2 ∆G°2

(c) 2 ∆G°1=∆G°2

(d) None of the above

Answer 1

For a reaction

G^o = -nFE^o

Where n is the number of moles of electrons involved , F is the faraday's constant and Eo = Potential

In reaction 1, Number of moles of electrons involved are 4

as : Oxidation state of H changes from +1 to o and that of Oxygen from -2 to 0

Here two moles of H₂O are involved. So number of electrons exchanged = 4

So, G^o₁ = -4FE⁰

Similarly in second reaction,

Number of moles of electrons involved = 2

So, G⁰₂ = -2FE^o = -4FE⁰ /2 = G^o₁ /2

G^o₁ = 2G^o₂

Option B