Problem 48 - General Chemistry

Question

The decomposition of ozone, \(\mathrm{O}_{3}\), to oxygen, \(\mathrm{O}_{2}\), is an exothermic reaction. What is the sign of \(q ?\) If you were to touch a flask in which ozone is decomposing to oxygen, would you expect the flask to feel warm or cool?

Step-by-Step Solution

Answer

The sign of \( q \) is negative, and the flask would feel warm.

Step 1: Understanding Exothermic Reactions

Exothermic reactions release energy into the surrounding environment. This means that during the reaction, heat is transferred from the system (the reacting ozone) to the surroundings (the flask and air).

Step 2: Determining the Sign of q

In thermodynamics, the sign of heat ( q ) is negative when heat is released by the system in an exothermic process. Therefore, since the decomposition of ozone is exothermic, q is negative.

Step 3: Predicting the Temperature of the Flask

Given that the reaction releases heat, the surroundings, including the flask, will absorb this heat. Therefore, if you were to touch the flask, it would feel warm because it is absorbing the released heat.

Key Concepts

Thermodynamics

Thermodynamics is the study of energy and how it moves within physical systems. It plays a crucial role in understanding exothermic reactions. In these reactions, chemical bonds rearrange in such a way that energy is released into the surroundings. This release of energy often results in a change in temperature.
Understanding the fundamentals of thermodynamics is essential for interpreting whether a reaction is exothermic or endothermic.

• Exothermic reactions release energy, making the reaction surroundings warmer.
• Endothermic reactions absorb energy, causing the surroundings to become cooler.

In the case of the decomposition of ozone to oxygen, the release of energy is evidence that the process is exothermic. Thus, thermodynamics provides the framework to predict how the energy transfer will affect the surrounding environment.

Heat Transfer

Heat transfer describes the process by which thermal energy moves from one place to another. During exothermic reactions, this energy is emitted from the system and absorbed by the surroundings.
The decomposition of ozone is a prime example of heat transfer in chemical reactions. In this case, the heat moves from the decomposing ozone molecules to the flask and air around it.

• If a reaction vessel feels warm to the touch, it indicates the system is losing heat to its surroundings.
• This transfer of heat aligns with the principles of thermodynamics, where heat must flow from a higher temperature region to a lower temperature region.

Understanding heat transfer helps us predict how system changes might affect its environment, such as why the flask becomes warm during an exothermic reaction like ozone decomposition.

Chemical Decomposition

Chemical decomposition is a type of chemical reaction where a compound breaks down into simpler substances. Ozone decomposition is a chemical decomposition reaction that results in the formation of oxygen from ozone.
In general, decomposition reactions require energy to break chemical bonds, but if more energy is released in forming new bonds than is required to break them, the reaction is exothermic.

• In ozone decomposition, the breaking of ozone ( ext{O}_{3} ) releases energy, as the resulting oxygen ( ext{O}_{2} ) formation is energetically favorable.
• The energy balance of breaking and forming bonds determines the overall release or absorption of energy in the reaction.

Understanding chemical decomposition processes allows us to predict the energetic shifts that occur during the reactions and their impacts on the surrounding environment.