2. Which of the following will be true when a pure substance in liquid phase freezes spontaneously?
DG, DH, and DS are all positive DG, DH, and DS are all positive
3. In which case MUST a reaction be spontaneous, independent of T?
DH = 0, DS must be positive. DH = 0, DS is negative. DS = 0, DH is positive. DH is negative, DS is positive. None of these
4. For the dissociation reaction of the acid HF: HF<-->H++ F -DS is observed to be negative. The BEST explanation for this is:
This is the expected result since each HF molecule produces two ions when it dissassociates Hydration of the ions produces the negative value of DS. The reation is expected to be exothermic and thus D should be negative. The reaction is expected to be endothermic and thus D should be negative. None of these can explain the negative value of DS.
5. Choose the correct statement.
Exothermic reactions are always spontaneous High temperature ensures a spontaneous reaction Free energy is independent of temperature A reaction with negative DS cannot be spontaneous none of the above
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