The **gas constant** is also known as the **molar**, **universal**, or **ideal gas constant**, denoted by the symbol *R* or *R* and is equivalent to the Boltzmann constant, but expressed in units of energy per temperature increment per *mole*, i.e. the pressure–volume product, rather than energy per temperature increment per *particle*. The constant is also a combination of the constants from Boyle's law, Charles's law, Avogadro's law, and Gay-Lussac's law. It is a physical constant that is featured in many fundamental equations in the physical sciences, such as the ideal gas law and the Nernst equation.

Physically, the gas constant is the constant of proportionality that relates the energy scale in physics to the temperature scale, when a mole of particles at the stated temperature is being considered. Thus, the value of the gas constant ultimately derives from historical decisions and accidents in the setting of the energy and temperature scales, plus similar historical setting of the value of the molar scale used for the counting of particles. The last factor is not a consideration in the value of the Boltzmann constant, which does a similar job of equating linear energy and temperature scales.

The gas constant R is defined as the Avogadro constant *N*_{A} multiplied by the Boltzmann constant *k*:

- ${\\displaystyle R=N_{\\rm {A}}k_{,}\\,}$

Since the 2019 redefinition of SI base units, which came into effect on 20 May 2019, both *N*_{A} and *k* are defined with exact numerical values when expressed in SI units. As a consequence, the value of the gas constant is exactly 8.31446261815324 J⋅K^{−1}⋅mol^{−1}.

Some have suggested that it might be appropriate to name the symbol *R* the **Regnault constant** in honour of the French chemist Henri Victor Regnault, whose accurate experimental data were used to calculate the early value of the constant; however, the origin of the letter *R* to represent of the constant is elusive.

The gas constant occurs in the ideal gas law, as follows:

- ${\\displaystyle PV=nRT=mR_{\\rm {specific}}T}$

where *P* is the absolute pressure (SI unit pascals), *V* is the volume of gas (SI unit cubic metres), *n* is the amount of gas (SI unit moles), *m* is the mass (SI unit kilograms) contained in *V*, and *T* is the thermodynamic temperature (SI unit kelvins). *R*_{specific} is the mass-specific gas constant. The gas constant is expressed in the same physical units as molar entropy and molar heat capacity.

Source: Gas constant

TIPS: To create new content for your website or blog...

- Enter the title of a Wikipedia article in the box above.
- Select your options using the checkboxes, or use default settings.
- Click the 'go' button to retrieve the article.
- Click the 'Copy Code' button to copy the source code of the article to your clipboard.
- Paste the source code into your favorite HTML editor.
- Edit the content to suit your needs.
- Publish your new content to your website or blog.
- IMPORTANT: Before publishing, be sure to make significant changes to avoid creating duplicate content.