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  • Consider a reaction that involves the conversion of solid calcium carbonate to solid calcium oxide and carbon dioxide gas: <img alt="\mathrm{CaCO}_3(\mathrm{~s}) \rightarrow \mathrm{CaO}(

Consider a reaction that involves the conversion of solid calcium carbonate to solid calcium oxide and carbon dioxide gas:

\mathrm{CaCO}_3(\mathrm{~s}) \rightarrow \mathrm{CaO}(\mathrm{s})+\mathrm{CO}_2(\mathrm{~g})

Which statement accurately describes the spontaneity of the reaction?

Option: 1

The spontaneity of the reaction is constant and it occurs spontaneously at all temperatures.


Option: 2

At any temperature is the reaction spontaneous.


Option: 3

The spontaneity of the reaction is temperature-dependent, where it becomes spontaneous at lower temperatures but non-spontaneous at higher temperatures.


Option: 4

The spontaneity of the reaction changes with temperature, where the reaction becomes spontaneous at high temperatures and nonspontaneous at low temperatures.


Answers (1)

best_answer

In order to determine the spontaneity of a reaction, we can use the concept of Gibbs free energy change, \Delta G. For any general process, the change in Gibbs free energy can be defined as \Delta \mathrm{G}=\Delta \mathrm{H}-\mathrm{T} \Delta \mathrm{S} . For a reaction to be spontaneous, \Delta G must be negative. Since the reaction in question involves an increase in entropy \text { (i.e., } \Delta S>0 \text { ), } we can say that the spontaneity of the reaction depends on the sign of \Delta H.

In this case, we know that the reaction involves the conversion of a solid to another solid and a gas, which suggests that the reaction is endothermic \text { (i.e., } \Delta H>0 \text { ),} we can say that the spontaneity of the reaction depends on the sign of \Delta H.

In this case, we know that the reaction involves the conversion of a solid to another solid and a gas, which suggests that the reaction is endothermic \text { (i.e., } \Delta H>0 \text { ). } Therefore, if \Delta H is greater than \frac{\Delta S}{T} then the reaction will be spontaneous at low temperatures and nonspontaneous at high temperatures. On the other hand, if \Delta H is less than \frac{\Delta S}{T}, then the reaction will be nonspontaneous at low temperatures and spontaneous at high temperatures.

Since the reaction involves the conversion of a solid to another solid and a gas, we can assume that the entropy change is positive. Therefore, we can conclude that the reaction is spontaneous at low temperatures and nonspontaneous at high temperatures. Hence, option 3 is correct.

Posted by

Devendra Khairwa

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