(a) At 298 K, Δf G^o(OF2, g)=+42 kJ mol^-1 From this value, can you say whether OF2 will form wh

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(a) At 298 K, Δf G^o(OF2, g)=+42 kJ mol^-1 From this value,...

(a) At $298 \mathrm{K}, \Delta_{\mathrm{f}} G^{\mathrm{o}}\left(\mathrm{OF}_{2}, \mathrm{g}\right)=+42 \mathrm{kJ} \mathrm{mol}^{-1}$ From this value, can you say whether $\mathrm{OF}_{2}$ will form when $F_{2}$ and $O_{2}$ combine at 298 K? (b) For the reaction: $$\mathrm{H}_{2} \mathrm{O}_{2}(1) \rightarrow \mathrm{H}_{2} \mathrm{O}(1)+\frac{1}{2} \mathrm{O}_{2}(\mathrm{g})$$ \[ \Delta_{\mathrm{r}} G^{\mathrm{o}}(298 \mathrm{K})=-117 \mathrm{kJ} \mathrm{mol}^{-1} . \text {Suggest why } \mathrm{H}_{2} \mathrm{O}_{2} \] does not decompose spontaneously on standing. Under what circumstances might $\mathrm{H}_{2} \mathrm{O}_{2}$ rapidly decompose at $298 \mathrm{K} ?$

(a) At $298 \mathrm{K}, \Delta_{\mathrm{f}} G^{\mathrm{o}}\left(\mathrm{OF}_{2}, \mathrm{g}\right)=+42 \mathrm{kJ} \mathrm{mol}^{-1}$
From this value, can you say whether $\mathrm{OF}_{2}$ will form when $F_{2}$ and $O_{2}$ combine at 298 K?
(b) For the reaction:
$$\mathrm{H}_{2} \mathrm{O}_{2}(1) \rightarrow \mathrm{H}_{2} \mathrm{O}(1)+\frac{1}{2} \mathrm{O}_{2}(\mathrm{g})$$
\[
\Delta_{\mathrm{r}} G^{\mathrm{o}}(298 \mathrm{K})=-117 \mathrm{kJ} \mathrm{mol}^{-1} . \text {Suggest why } \mathrm{H}_{2} \mathrm{O}_{2}
\]
does not decompose spontaneously on standing. Under what circumstances might $\mathrm{H}_{2} \mathrm{O}_{2}$ rapidly decompose at $298 \mathrm{K} ?$

Key Concepts

Catalysis

Catalysis involves the use of a catalyst to lower the activation energy of a reaction, thereby accelerating its rate without altering the overall thermodynamics (free energy change) of the reaction. Catalysts are important for enabling reactions that are thermodynamically favorable but kinetically slow under normal conditions.

Activation Energy

Activation energy is the minimum energy required for reactants to successfully collide and form products. High activation energy can prevent a reaction that is thermodynamically downhill from occurring quickly, as fewer molecules have sufficient energy to overcome this barrier.

Thermodynamic vs Kinetic Control

Thermodynamic control refers to the overall energy changes of a reaction (i.e., the difference in free energy between reactants and products), whereas kinetic control is governed by the activation energy barrier that must be overcome for the reaction to proceed. A reaction may be thermodynamically favored but kinetically hindered, meaning it will not occur at an observable rate without additional influences.

Reaction Spontaneity

The spontaneity of a chemical reaction is judged by the sign of the Gibbs free energy change. For a reaction to be spontaneous under standard conditions, ?G must be negative. Even if a reaction is thermodynamically favorable (negative ?G), it may not proceed rapidly if other factors inhibit the reaction.

Gibbs Free Energy

Gibbs free energy (?G) is a thermodynamic potential that combines enthalpy and entropy effects, determining whether a process or reaction can occur spontaneously at constant temperature and pressure. A negative ?G indicates a spontaneous process, while a positive ?G suggests non-spontaneity under standard conditions.

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