Question

Consider the Gibbs energies at 25 ∘ C. Substance Δ G ∘ f ( kJ ⋅ mol − 1 ) Ag + ( aq ) 77.1 Cl − ( aq ) − 131.2 AgCl ( s ) − 109.8 Br − ( aq ) − 104.0 AgBr ( s ) − 96.9 (a) Calculate Δ G ∘ rxn for the dissolution of AgCl ( s ) .

Answer 1

The ΔG° for the dissolution of AgCl solid is 55.7 kJ/mol.

Step-by-step explanation:

The Gibbs free energy of the reaction is given by :

`\Delta G_(rxn)^o=\sum[\Delta G^o_(f)]_(products)-\sum[\Delta G^o_(f)]_(reactants)`

So for reaction :

`AgCl(s)\rightarrow Ag^+(aq)+Cl^-(aq)`

Gibbs free energy of formation of silver ions =
`\Delta G^o_(f,Ag^+)=77.1 kJ/mol`

Gibbs free energy of formation of chloride ions =
`\Delta G^o_(f,Cl^-)=-131.2 kJ/mol`

Gibbs free energy of formation of silver chloride solid=
`\Delta G^o_(f,AgCl)=-109.8 kJ/mol`

The Gibbs free energy of the reaction of dissolution of AgCl :
`\Delta G_(rxn)^o` :

`\Delta G_(rxn)^o=[77.1 kJ/mol+(-131.2 kJ/mol)]-[-109.8 kJ/mol]`

`=55.7 kJ/mol`

The ΔG° for the dissolution of AgCl solid is 55.7 kJ/mol.