Question 1

What is the ideal gas law?

Accepted Answer

The ideal gas law PV = nRT describes the behavior of an ideal gas, where P is pressure (Pa), V is volume (m³), n is the number of moles, R is the universal gas constant (8.314 J/mol·K), and T is temperature in Kelvin. It combines Boyle's, Charles's, and Avogadro's laws into a single equation.

Question 2

When does the ideal gas law break down?

Accepted Answer

The ideal gas law assumes no intermolecular forces and negligible molecular volume. It breaks down at very high pressures (molecules forced close together), very low temperatures (intermolecular forces become significant), and near the condensation point. For these conditions, the Van der Waals equation or other real gas equations provide better accuracy.

Question 3

Why must temperature be in Kelvin?

Accepted Answer

The ideal gas law requires absolute temperature because pressure and volume are proportional to absolute temperature. At 0 K (absolute zero), an ideal gas would have zero volume and zero pressure. Using Celsius would give negative temperatures that produce nonsensical negative volumes or pressures. Convert by adding 273.15: K = °C + 273.15.

Question 4

What is the universal gas constant?

Accepted Answer

The universal gas constant R = 8.314462 J/(mol·K) relates energy to temperature on a per-mole basis. It equals the product of Boltzmann's constant (k_B) and Avogadro's number (N_A). R appears in many thermodynamic equations beyond the ideal gas law, including entropy calculations and chemical equilibrium expressions.

Ideal Gas Law Calculator (PV = nRT)

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