Definition

1. Noun:
   • A fundamental physical constant: The universal gas constant is a constant of proportionality that appears in the ideal gas law, relating the pressure, volume, temperature, and amount of an ideal gas. Its value is approximately 8.314462618 joules per kelvin per mole (J·K⁻¹·mol⁻¹).

Usage

• The universal gas constant is a fixed value used in thermodynamic and physical chemistry equations to describe the behavior of gases under ideal conditions.
• It is symbolized by the capital letter R.
• It is used in the ideal gas law: PV = nRT, where P is pressure, V is volume, n is the amount of substance (in moles), and T is absolute temperature.

Examples of Usage

• In an equation:
  • To calculate the pressure, you need to know the volume, temperature, number of moles, and the universal gas constant.
  • The value of the universal gas constant, R, is a cornerstone of the kinetic theory of gases.
• In scientific explanation:
  • The universal gas constant provides the necessary scaling factor to relate the microscopic energy of molecules to macroscopic quantities like pressure and volume.

Advanced Usage

• In different unit systems: While its value in SI units is ~8.314 J·K⁻¹·mol⁻¹, the universal gas constant can be expressed in other units (e.g., L·atm·K⁻¹·mol⁻¹ ≈ 0.08206) depending on the units used for pressure and volume in a calculation.
• Relation to Boltzmann constant: The universal gas constant (R) is related to the Boltzmann constant (kB * NA is the Avogadro constant. This links the macroscopic gas constant to the microscopic world of individual particles.

Variants and Related Words

• Gas constant (R): This is the most common shorthand name for the universal gas constant.
• Ideal gas constant: A synonym emphasizing its use in the ideal gas law.
• Molar gas constant: A name highlighting that its value is defined per mole of substance.

Synonyms

• Gas constant
• Ideal gas constant
• Molar gas constant
• R (the symbol)

Related Phrases and Concepts

• Ideal gas law: The primary equation (PV = nRT) where the universal gas constant is used.
• Boltzmann constant (k_B): The fundamental constant relating temperature to the average kinetic energy of particles; related to R by Avogadro's number.
• Avogadro constant (NA): The number of constituent particles in one mole of a substance; links R to kB.

Noun

1. (physics) the universal constant in the gas equation: pressure times volume = R times temperature; equal to 8.3143 joules per kelvin per mole