Question

Use the data given here to calculate the values of delta G rxn at 25 degrees celcius for the reaction described by the equation.

compound      delta G(f) kj/mol

A                    +387.7

B                     +657.6

C                      +402.0

A + B yields C

delta G rxn= ? kj/mol

so find delta G rxn.

If ?H°rxn and ?S°rxn are both negative values, what drives the spontaneous reaction and in what direction at standard conditions?

Answer 1

1)

Given:

Gof(A) = 387.7 KJ/mol

Gof(B) = 657.6 KJ/mol

Gof(C) = 402.0 KJ/mol

Balanced chemical equation is:

A + B ---> C

?Go rxn = 1*Gof(C) - 1*Gof( A) - 1*Gof(B)

?Go rxn = 1*(402.0) - 1*(387.7) - 1*(657.6)

?Go rxn = -643.3 KJ

Answer: -643.3 KJ

2)

?Go rxn is negative, so forward reaction is spontaneous

we have:

?Go rxn = ?Ho rxn - T*?So rxn

Since both ?Ho rxn and ?So rxn are negative,

?Go rxn is becoming negative due to ?Ho rxn

so,

?Ho rxn is driving spontaneous reaction in forward direction