Chemistry · The second law of thermodynamics: Spontaneity of processes, Delta S of the universe and Delta G of the system as criteria for spontaneity
Select the correct statement(s): This question has multiple correct options
Select the correct statement(s): This question has multiple correct options
- A. When temperature is reised, a point will be reached where the graph crosses the \( \Delta G=0 \) line. Below this temperature, the free energy of formatin of the oxide is negative, so the oxide is stable
- B. When temperature is raised, a point will be reached where the graph crosses the \( \Delta G=0 \) line. Above this temperature, the free energy of formation of the oxide is positive, and the oxide becomes unstable, and should decompose into the metal and dioxygen.
- C. Theoretically, all oxides can be decomposed to give the metal and dioxygen if.a sufficiently high temperature can be attained.
- D. Theoretically, all oxides cannot be decomposed to give the metal and dioxygen if a sufficiently high temperature can he attaincd
Step-by-step solution
For most oxides, decomposition is endothermic and has a positive entropy change due to release of O2 gas. Thus, ΔG = ΔH - TΔS becomes negative at high T, making decomposition spontaneous. Although exceptions like CO exist (where ΔS is negative), the statement is generally accepted for common metal oxides.
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