Problem 87 - Chemistry Matter and Change

Question

Apply Smelling salts, sometimes used to revive a person who is unconscious, are made of ammonium carbonate. The equation for the endothermic decomposition of ammonium carbonate is as follows. $$ \left(\mathrm{NH}_{4}\right)_{2} \mathrm{CO}_{3}(\mathrm{s}) \rightleftharpoons 2 \mathrm{NH}_{3}(\mathrm{g})+\mathrm{CO}_{2}(\mathrm{g})+\mathrm{H}_{2} \mathrm{O}(\mathrm{g}) $$ .Would you expect smelling salts to work as well on a cold winter day as on a warm summer day? Explain your answer.

Step-by-Step Solution

Answer

The effectiveness of smelling salts would be greater on a warm summer day than on a cold winter day. This is because the endothermic decomposition of ammonium carbonate proceeds more efficiently when there is more heat available, producing a higher concentration of the gaseous products (ammonia, carbon dioxide, and water vapor) that enable the smelling salts to work effectively.

Step 1: Understanding Endothermic Reactions

In endothermic reactions, heat is absorbed from the surroundings into the reaction system. This means that the reaction requires heat to proceed. So, when the temperature increases, the rate of the reaction tends to increase as there is more heat available for the reaction to proceed.

Step 2: Analyzing the given equation

The decomposition of ammonium carbonate is an endothermic reaction, as shown below: \[ \left(\mathrm{NH}_{4}\right)_{2} \mathrm{CO}_{3}(\mathrm{s}) \rightleftharpoons 2 \mathrm{NH}_{3}(\mathrm{g})+\mathrm{CO}_{2}(\mathrm{g})+\mathrm{H}_{2} \mathrm{O}(\mathrm{g}) \] This equation indicates that solid ammonium carbonate decomposes into gaseous ammonia, carbon dioxide, and water vapor. The double arrow symbol (\(\rightleftharpoons\)) signifies that the reaction can proceed in both directions (forward and reverse).

Step 3: Considering the effect of temperature on the reaction

Since the decomposition of ammonium carbonate is an endothermic reaction, it requires heat to proceed. On a warm summer day, there is a higher amount of heat available, which increases the rate of the reaction. In contrast, on a cold winter day, there is less heat available in the surroundings, leading to a slower reaction rate.

Step 4: Comparing the effectiveness of smelling salts at different temperatures

As smelling salts rely on the decomposition of ammonium carbonate to produce gaseous ammonia, carbon dioxide, and water vapor (which are responsible for the reviving effect), we can conclude that the effectiveness of smelling salts would be greater on a warm summer day than on a cold winter day. This is because the endothermic reaction proceeds more efficiently when there is more heat available, producing a higher concentration of the gaseous products that enable the smelling salts to work effectively.

Key Concepts

Ammonium Carbonate Decomposition

Ammonium carbonate, often found in smelling salts, is an interesting chemical compound due to its ability to decompose easily at certain temperatures. This decomposition is represented by the chemical reaction: \[\left(\mathrm{NH}_{4}\right)_{2} \mathrm{CO}_{3}(\mathrm{s}) \rightleftharpoons 2 \mathrm{NH}_{3}(\mathrm{g})+\mathrm{CO}_{2}(\mathrm{g})+\mathrm{H}_{2} \mathrm{O}(\mathrm{g}) \] Here, solid ammonium carbonate breaks down into gaseous ammonia, carbon dioxide, and water vapor. The reaction is reversible, indicated by the arrow \((\rightleftharpoons)\).

• Ammonia \((\mathrm{NH}_{3})\) is the key component that causes the characteristic pungent aroma of smelling salts.
• Carbon dioxide \((\mathrm{CO}_{2})\) and water vapor \((\mathrm{H}_{2}\mathrm{O} (\mathrm{g}))\) are also produced as by-products.

The decomposition of ammonium carbonate is an endothermic reaction, meaning it absorbs heat from its surroundings to proceed. This is essential for the functionality of smell salts, as a greater release of the gaseous products aids in reviving an unconscious person.

Temperature Effect on Reactions

Temperature plays a crucial role in chemical reactions, particularly in endothermic reactions such as the decomposition of ammonium carbonate. An endothermic reaction absorbs heat, making the process reliant on environmental conditions. During warmer temperatures, like those on a sunny summer day, more heat is available in the surroundings. This extra heat helps speed up the endothermic reaction, facilitating a quicker breakdown of ammonium carbonate into ammonia, carbon dioxide, and water vapor. Conversely, cooler temperatures, like those experienced on a cold winter day, provide less ambient heat.

• Warmer temperatures mean faster reaction rates because of increased heat absorption.
• Cooler temperatures slow down the decomposition process due to reduced heat availability.

Therefore, the climatic conditions directly influence the effectiveness of reactions that rely on heat, such as those occurring with smelling salts.

Reaction Rate and Temperature

The reaction rate signifies how quickly a chemical reaction proceeds, and temperature is one of the primary factors that influence this rate. In the context of endothermic reactions like ammonium carbonate decomposition, temperature changes can significantly affect how efficiently the reaction occurs.

• Increased temperature typically leads to an increase in the reaction rate because the molecules have more energy, moving faster and colliding more frequently.
• In an endothermic reaction, such as the one with ammonium carbonate, more heat means more effective decomposition into the gaseous by-products.
• Conversely, a lower temperature results in slower molecular movement, fewer collisions, and thus a slower reaction rate.

This relationship between reaction rate and temperature is why you might observe that smelling salts are noticeably more effective in warmer conditions. More gas is released more quickly when it's hot, providing a stronger and faster reviving stimulus.