Universal gas constant

Definition

The universal gas constant, denoted as $R$, is a fundamental constant in the ideal gas law, relating the energy scale to temperature when considering moles of gas. Its value is approximately 8.314 J/(mol·K).

5 Must Know Facts For Your Next Test

1. The universal gas constant $R$ has a value of 8.314 J/(mol·K) in SI units.
2. It appears in the ideal gas law equation: $PV = nRT$, where $P$ is pressure, $V$ is volume, $n$ is the number of moles, and $T$ is temperature.
3. The value of $R$ can also be expressed in other units such as L·atm/(mol·K), which equals approximately 0.0821.
4. $R$ provides a bridge between macroscopic and microscopic physical quantities, linking thermodynamic properties to molecular behavior.
5. The derivation of the universal gas constant involves Boltzmann's constant ($k_B$) and Avogadro's number ($N_A$): $R = k_B N_A$.

Review Questions

• What is the numerical value of the universal gas constant in SI units?
• How does the universal gas constant relate to Boltzmann's constant and Avogadro's number?
• In which equation does the universal gas constant appear, and what are its variables?

Related terms

Ideal Gas Law: An equation of state for an ideal gas: $PV = nRT$, describing the relationship between pressure, volume, temperature, and moles of a gas.

Boltzmann's Constant: A physical constant relating the average kinetic energy of particles in a gas with temperature: approximately \(1.38 \times10^{-23} \\ \text{J/K}\).

Avogadro's Number: $6.022 \times10^{23}$ mol\(^{-1}\), representing the number of atoms or molecules in one mole of substance.