Question

Under what conditions is the ideal-gas assumption suitable for real gases?

Short answer

Answer: The ideal gas assumption is more suitable for real gases under high temperatures, low pressures, and for gases with simple molecular structures.

Step-by-step solution

Understand the ideal-gas assumption and real gases

The ideal-gas assumption is a simplified model of gas behavior. This model is based on the following assumptions: 1. Gas molecules are considered point masses that do not occupy any volume. 2. The forces between gas molecules are neglected unless during a collision. 3. Gas molecules undergo elastic collisions, meaning there is no exchange of internal energy. Real gases, however, have actual volumes and forces between molecules can play an important role in some situations. Therefore, it is essential to determine under which conditions the ideal-gas assumption can be valid for real gases.

Consider temperature

As the temperature increases, the kinetic energy of the gas molecules gets larger, and the forces between the molecules, especially the attractive forces, become less significant. This makes the molecules behave more like an ideal gas - bouncing around with little interaction. Hence, the ideal-gas assumption is more applicable at high temperatures.

Consider pressure

Pressure is defined as the force exerted by the gas molecules on a given area. When the pressure is low, the gas molecules are relatively far apart from one another, and the effects of volume and intermolecular forces are negligible. Under low-pressure conditions, real gases tend to behave more similarly to ideal gases, making the ideal-gas assumption suitable.

Consider the nature of a specific gas

Some gases inherently behave more like ideal gases than others. For example, monatomic gases like helium and noble gases often show more ideal behavior than complex molecules like CO2. It is essential to keep in mind the nature of the gas when assessing the applicability of the ideal-gas assumption. In summary:

Conditions for the ideal-gas assumption to be suitable for real gases

The ideal-gas assumption is more applicable for real gases under the following conditions: 1. High temperatures 2. Low pressures 3. For gases with simple molecular structures