Question

If \[{{C}}{{{l}}_{{2}}}{{{O}}_\,}\,{{,}}\,{{B}}{{{r}}_{{2}}}{{O,}}\,\,{{{I}}_{{2}}}{{O}}\,\]have positive value of \[{{\Delta G}}\] (free energy) indicating that:
A. These oxides are stable.
B. These oxides are unstable and changes to \[{{{X}}_{{2}}}\;{{ and }}\;{{{O}}_{{2}}}{{.}}\]
C. These disproportionate into \[{{{X}}^ - }{{ and\; X}}{{{O}}^ - }{{.}}\]
D. These oxides can form interhalogen compounds.

Answer 1

Hint: Positive \[{{\Delta G}}\]means the reaction is nonspontaneous and negative \[{{\Delta G}}\] means the reaction is spontaneous. In a non-spontaneous process, the product formed is unstable i.e., the energy of the product is more than that of reactants.

Complete step by step answer:
Gibbs free energy helps us to predict the spontaneity of reaction on the basis of enthalpy and entropy values. When the reaction is exothermic, enthalpy of the system is negative and Gibbs free energy negative i.e., exothermic reactions are spontaneous. In the case of endothermic reactions, the enthalpy of the system is positive, the process is spontaneous under two conditions, the temperature is very high to make the Gibbs energy value negative or entropy change is very high to make the Gibbs free energy negative. This can be easily understood by the equation,
\[{{\Delta }}{{{G}}_{{{sys}}}}{{\; = \;\Delta }}{{{H}}_{{{sys}}}}{{-T\Delta }}{{{S}}_{{{sys}}}}\]
\[{{\Delta }}{{{G}}_{{{sys}}}}{{\; = }}\] Gibbs energy change of the system
\[{{\Delta }}{{{H}}_{{{sys}}}}{{\; = }}\] Enthalpy change of the system
\[{{\Delta }}{{{S}}_{{{sys}}}}{{\; = }}\] Entropy change of the system
\[{{T\; = }}\]Temperature of the system
Here, the given process is nonspontaneous so the product is unstable and they react back to form the reactants.

So, the correct answer is Option B.

Additional Information:
Entropy is a measure of disorderness of the system. In case of a spontaneous process, the total entropy change is greater than zero. If the standard free energy, \[{{\Delta G}}\] is zero, then the products and reactants are equally favored in equilibrium.

Note: Gibbs free energy measures useful work at a constant temperature and pressure from the thermodynamic system. The Gibbs free energy is equal to the work exchanged by the system with its surroundings when the system undergoes a change from an initial state to a final state, subtracted by the work of the pressure force.