medium · MCAT chem-phys
A clinician uses a chemical cold pack to treat a patient's sprained ankle. The pack works by dissolving ammonium nitrate in water, a process that is endothermic (ΔH > 0).
If the cold pack works spontaneously, what must be true about the entropy change (ΔS) of the system?
- ΔS must be zero, as the process is driven solely by heat transfer.
- ΔS must be positive, such that TΔS > ΔH.
- ΔS does not affect spontaneity in processes involving phase changes.
- ΔS must be negative to compensate for the positive enthalpy.
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