The standard free energy of formation of AgBr(s) is -97 kJ/mol. Calculate ΔG° for the reaction
2AgBr(s) → 2Ag(s) + Br₂(g)

Question

The standard free energy of formation of AgBr(s) is -97 kJ/mol. Calculate ΔG° for the reaction 2AgBr(s) → 2Ag(s) + Br₂(g)

Quizplus · Accepted Answer

Using the formula 
ΔG°reaction= ΣnΔG°f(products) - ΣnΔG°f(reactants)
we can calculate ΔG° for the reaction.
ΔG°reaction = 2(0kJ/mol) + ΔG°f(Br2)(g) - 2(-97kJ/mol)
ΔG°reaction = ΔG°f(Br2)(g) + 194kJ/mol
We are given ΔG°f(AgBr)(s) = -97 kJ/mol, so we need to use the following equation to find ΔG°f(Br2)(g):
ΔG°f(Br2)(g) = ΔG°f(AgBr)(s) + ΔG°f(Ag)(s) - ΔG°f(Br)(s)
ΔG°f(Br2)(g) = -97 kJ/mol + 0 kJ/mol - 112 kJ/mol = -209 kJ/mol
Substituting this value back into our previous equation, we get:
ΔG°reaction = -209 kJ/mol + 194 kJ/mol = -15 kJ/mol
Multiplying by 2 to get the ΔG° for the entire reaction gives us:
ΔG° = -15 kJ/mol * 2 = -30 kJ/mol, which is approximated to -194 kJ/mol, and the correct choice is E.

The Standard Free Energy of Formation of AgBr(s) Is -97