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 decomposition of ammonium carbonate is an endothermic reaction, increasing the temperature will shift the equilibrium towards the products. This leads to an increase in the concentration of ammonia (NH3), which in turn increases the smell of ammonia. Therefore, the smell of ammonia will increase as the temperature is increased.

Step-by-step solution

Understand the reaction and Le Chatelier's principle

We are given the decomposition reaction of ammonium carbonate as: \[ \left(\mathrm{NH}_{4}\right)_{2} \mathrm{CO}_{3}(s) \rightleftharpoons 2 \mathrm{NH}_{3}(g)+\mathrm{CO}_{2}(g)+\mathrm{H}_{2} \mathrm{O}(g) \] This reaction is endothermic, which means it absorbs heat from the surroundings. According to Le Chatelier's principle, if we increase the temperature in an endothermic reaction, the equilibrium will shift in the direction that absorbs the added heat. In this case, the equilibrium will shift towards the products.

Determine the effect of increasing temperature

Since the reaction is endothermic, increasing the temperature will lead to a shift in equilibrium towards the products. This is to counteract the increase in temperature by absorbing the heat through the endothermic reaction. As a result, the concentrations of the products (NH3, CO2, and H2O) will increase.

Relate the effect to the smell of ammonia

When the concentration of ammonia (NH3) increases, it implies that more ammonia is released as a gas. As the smell of ammonia is due to the presence of ammonia gas, if the concentration increases, it indicates that the smell of ammonia will increase as well. In conclusion, as the temperature is increased in an endothermic reaction like the decomposition of ammonium carbonate, the smell of ammonia will increase.