Real gases follow _______.
Van der Waals equation of state
Let's analyze the behavior of real gases and compare it with the options provided.
The ideal gas law, given by the equation $\text{PV} = \text{nRT}$, is a simple model that describes the behavior of hypothetical ideal gases. An ideal gas is assumed to consist of point particles that do not interact with each other except during perfectly elastic collisions, and the volume occupied by the gas molecules themselves is considered negligible compared to the volume of the container.
However, real gases are different from ideal gases. In real gases:
These differences become significant at high pressures (where molecules are close together and their volume becomes comparable to the container volume) and low temperatures (where intermolecular forces become more dominant). Therefore, real gases do not perfectly follow the ideal gas law under all conditions.
Because real gases deviate from ideal behavior, a more accurate equation of state is needed to describe their properties. The Van der Waals equation is one such equation, developed by Johannes Diderik van der Waals. It modifies the ideal gas law by introducing two correction terms:
The Van der Waals equation of state is typically written as:
$\left(P + \frac{an^2}{V^2}\right)(V - nb) = nRT$
Where:
The constants $a$ and $b$ are specific to each gas.
Both Gay-Lussac's law and Charles's law are part of the empirical gas laws that led to the ideal gas law, and they are accurate only for ideal gases or real gases behaving ideally (e.g., at low pressure and high temperature).
Therefore, among the given options, the Van der Waals equation of state is specifically designed to describe the behavior of real gases, accounting for their deviations from ideality.
| Equation/Law | Describes |
|---|---|
| Ideal Gas Law ($PV=nRT$) | Ideal gases (hypothetical) |
| Van der Waals Equation | Real gases (with corrections) |
| Gay-Lussac's Law | Ideal gases (P-T relationship at constant V) |
| Charles's Law | Ideal gases (V-T relationship at constant P) |
| Newton's Laws | Motion and forces (not gas state equation) |
Based on the analysis, real gases are best described by the Van der Waals equation of state among the given choices.
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