Question

Old-fashioned "smelling salts" consist of ammonium carbonate, \(\left(\mathrm{NH}_{4}\right)_{2} \mathrm{CO}_{3} .\) The reaction for the decomposition of ammonium carbonate $$ \left(\mathrm{NH}_{4}\right)_{2} \mathrm{CO}_{3}(s) \rightleftharpoons 2 \mathrm{NH}_{3}(g)+\mathrm{CO}_{2}(g)+\mathrm{H}_{2} \mathrm{O}(g) $$ is endothermic. Would the smell of ammonia increase or decrease as the temperature is increased?

Short answer

As the temperature increases, the smell of ammonia will increase. This is because the decomposition of ammonium carbonate is endothermic, and according to Le Chatelier's principle, the equilibrium will shift towards the production of more ammonia gas when the temperature is increased.

Step-by-step solution

Identify the endothermic reaction

The reaction for the decomposition of ammonium carbonate is endothermic, which means it absorbs heat: \[ \left(\mathrm{NH}_{4}\right)_{2} \mathrm{CO}_{3}(s) \rightleftharpoons 2 \mathrm{NH}_{3}(g)+\mathrm{CO}_{2}(g)+\mathrm{H}_{2} \mathrm{O}(g) \]

Apply Le Chatelier's principle to the reaction

According to Le Chatelier's principle, if we increase the temperature, the equilibrium will shift in the direction that absorbs the heat. In this case, that is the direction of the endothermic reaction, which leads to the formation of ammonia (NH₃), carbon dioxide (CO₂), and water (H₂O) gases.

Determine the effect on the smell of ammonia

As the temperature increases, the equilibrium shifts in the direction of the endothermic reaction, producing more ammonia (NH₃), carbon dioxide (CO₂), and water (H₂O) gases. Since ammonia is responsible for the smell, an increase in its concentration directly corresponds to an increase in the smell.

Conclusion

As the temperature increases, the smell of ammonia will also increase due to a shift in the equilibrium position towards the production of more ammonia gas, according to Le Chatelier's principle.

Key concepts

Endothermic Reactions

An endothermic reaction is a type of chemical reaction that requires an input of energy in the form of heat to proceed. Simply put, it absorbs heat from its surroundings. When a reaction is endothermic, the products are at a higher energy level than the reactants, meaning energy has been taken in during the process.

In the case of the decomposition of ammonium carbonate, the reaction is endothermic. This means that the breaking down of ammonium carbonate into ammonia, carbon dioxide, and water vapor requires heat.

You can think of endothermic reactions like a baking process in the kitchen. Just as you need heat for your cake to rise, an endothermic reaction needs heat to proceed. In this context, adding heat to the system drives the reaction forward, enabling more of the reactants to transition into products.

Equilibrium Shift

In chemical reactions, equilibrium refers to the state where the rates of the forward and reverse reactions are equal, meaning the concentration of reactants and products remains constant over time. Le Chatelier's Principle helps us predict how a system at equilibrium will respond to changes in temperature, pressure, or concentration of components.

For endothermic reactions like the decomposition of ammonium carbonate, an increase in temperature causes the equilibrium to shift towards the direction where heat is absorbed, i.e., the endothermic direction. This is because the system looks to counteract the added heat by favoring the process that absorbs it.

In summary, when you increase the temperature in our reaction involving ammonium carbonate, the system compensates by shifting the equilibrium to produce more ammonia, carbon dioxide, and water vapor, enhancing the reaction's progression forward.

Ammonium Carbonate Decomposition

The decomposition of ammonium carbonate is an illustrative example of an endothermic reaction. The process involves a solid transforming into gas products, specifically ammonia, carbon dioxide, and water vapor.

The chemical equation representing this decomposition is:
\[\left(\mathrm{NH}_{4}\right)_{2} \mathrm{CO}_{3}(s) \rightleftharpoons 2 \mathrm{NH}_{3}(g)+\mathrm{CO}_{2}(g)+\mathrm{H}_{2} \mathrm{O}(g) \] This reaction is crucial for understanding how temperature impacts chemical systems. As the reaction absorbs heat, increasing the temperature leads to more ammonia gas formation, which is detectable due to its strong smell.

Old-fashioned smelling salts often contain ammonium carbonate. When subjected to higher temperatures, they decompose more readily, releasing ammonia vapor. This increase in ammonia results in a noticeable, stronger smell. Thus, adjusting the thermal conditions can directly influence the effectiveness and intensity of reactions involving ammonium carbonate.