Question

Under what conditions gases generally deviate from ideal behaviour? (a) At high temperature and low pressure (b) At low temperature and high pressure (c) At high temperature and high pressure (d) At low temperature and low pressure

Short answer

Gases generally deviate from ideal behaviour at low temperature and high pressure.

Step-by-step solution

Understanding Ideal Gas Behavior

An ideal gas is a theoretical gas that follows the ideal gas laws exactly, without any deviations. The behavior is described by PV=nRT, where P is the pressure, V is the volume, n is the number of moles, R is the gas constant, and T is the temperature. Real gases approximate ideal gas behavior under certain conditions.

Conditions for Non-Ideal Gas Behavior

Real gases deviate from ideal behavior under conditions where the gas particles interact significantly with each other. These conditions typically include high pressure, which forces particles closer together, and low temperature, which reduces the kinetic energy of the particles, leading to increased intermolecular forces.

Analyzing the Given Options

Comparing the given options with the conditions where interactions between gas particles become significant, we look for the choice that includes high pressure and low temperature.

Final Answer

The conditions under which gases generally deviate from ideal behavior are high pressure and low temperature. This is because the particles are close together and their kinetic energy is lowered, allowing intermolecular forces to become noticeable.

Key concepts

Ideal Gas Law

The ideal gas law is a foundational principle in understanding the behavior of gases. It's articulated as the reliable equation \( PV=nRT \), with \( P \) being the pressure, \( V \) the volume, \( n \) the number of moles, \( R \) the gas constant, and \( T \) the temperature. The equation implies that, for a fixed amount of gas, the pressure and volume are directly proportionate to the temperature. This law assumes that gas particles are point masses with no volume and no interaction with each other.

However, this is a simplification that doesn't always hold up in the real world; real gases have volume and do exert forces on each other. It's crucial for students to realize that ideal gas behavior is a good approximation when the particles are far apart and moving at high speeds relative to their intermolecular forces, which is generally at high temperatures and low pressures. This means that gases behave 'ideally' in conditions where intermolecular forces and the volume of particles are negligible compared to the overall system.

Real Gases Deviation

While the ideal gas law provides a simple model, real gases often deviate from this ideal behavior. This deviation occurs primarily due to the presence of intermolecular forces and the finite volume occupied by gas molecules. Conditions that promote a noticeable deviation include low temperatures, where the molecules have less kinetic energy and thus, intermolecular attractions become more significant. Also, at high pressures, molecules are forced closer together, which increases the effect of these forces.

Understanding when and why real gases deviate from ideal behavior is essential for students navigating complex problems in thermodynamics and physical chemistry. It helps students appreciate the limitations of models and the nuances of real-world applications. For instance, engineers and scientists must account for these deviations when designing systems that operate under a wide range of temperatures and pressures.

Intermolecular Forces

Intermolecular forces are the forces of attraction or repulsion that act between neighboring particles: atoms, molecules, or ions. These forces explain a variety of physical properties of compounds, including boiling points, melting points, and solubilities. There are several types of intermolecular forces, such as London dispersion forces, dipole-dipole interactions, and hydrogen bonding. They are weaker than the intramolecular forces that hold atoms together within a molecule but are critical to the behavior of substances.

At low temperatures, the kinetic energy of the gas molecules is reduced, which means these forces have a more substantial impact on the behavior of the gas. Understanding intermolecular forces enables students to predict the behavior of substances under various conditions and is crucial in explaining why real gases deviate from the ideal model. It's these forces that lead to the observed deviation in gas behavior when conditions stray from the high-temperature and low-pressure ideal.