Gas constant

(Redirected from Universal gas constant)
Jump to: navigation, search
Values of R Units
(V·P·T-1·n-1)
8.314472 J·K-1·mol-1
0.0820574587 L·atm·K-1·mol-1
8.20574587 × 10-5 m3·atm·K-1·mol-1
8.314472 cm3·MPa·K-1·mol-1
8.314472 L·kPa·K-1·mol-1
8.314472 m3·Pa·K-1·mol-1
62.3637 mmHg·K-1·mol-1
62.3637 L·Torr·K-1·mol-1
83.14472 L·mbar·K-1·mol-1
1.987 cal·K-1·mol-1
6.132440 lbf·ft·K-1·g·mol-1
10.7316 ft3·psi· °R-1·lb-mol-1
0.7302 ft3·atm·°R-1·lb-mol-1
1716 (Air only) ft·lb·°R-1·slug-1
286.9 (Air only) N·m·kg-1·K-1
286.9 (Air only) J·kg-1·K-1
999 ft3·mmHg·K-1·lb-mol-1

WikiDoc Resources for Gas constant

Articles

Most recent articles on Gas constant

Most cited articles on Gas constant

Review articles on Gas constant

Articles on Gas constant in N Eng J Med, Lancet, BMJ

Media

Powerpoint slides on Gas constant

Images of Gas constant

Photos of Gas constant

Podcasts & MP3s on Gas constant

Videos on Gas constant

Evidence Based Medicine

Cochrane Collaboration on Gas constant

Bandolier on Gas constant

TRIP on Gas constant

Clinical Trials

Ongoing Trials on Gas constant at Clinical Trials.gov

Trial results on Gas constant

Clinical Trials on Gas constant at Google

Guidelines / Policies / Govt

US National Guidelines Clearinghouse on Gas constant

NICE Guidance on Gas constant

NHS PRODIGY Guidance

FDA on Gas constant

CDC on Gas constant

Books

Books on Gas constant

News

Gas constant in the news

Be alerted to news on Gas constant

News trends on Gas constant

Commentary

Blogs on Gas constant

Definitions

Definitions of Gas constant

Patient Resources / Community

Patient resources on Gas constant

Discussion groups on Gas constant

Patient Handouts on Gas constant

Directions to Hospitals Treating Gas constant

Risk calculators and risk factors for Gas constant

Healthcare Provider Resources

Symptoms of Gas constant

Causes & Risk Factors for Gas constant

Diagnostic studies for Gas constant

Treatment of Gas constant

Continuing Medical Education (CME)

CME Programs on Gas constant

International

Gas constant en Espanol

Gas constant en Francais

Business

Gas constant in the Marketplace

Patents on Gas constant

Experimental / Informatics

List of terms related to Gas constant


Overview

The gas constant (also known as the molar, universal, or ideal gas constant, usually denoted by symbol R) is a physical constant which is featured in a large number of fundamental equations in the physical sciences, such as the ideal gas law and the Nernst equation. It is equivalent to the Boltzmann constant, but expressed in units of energy (i.e. the pressure-volume product) per kelvin per mole (rather than energy per kelvin per particle).

Its value is:

R = 8.314472(15) J · K-1 · mol-1

The two digits in parentheses are the uncertainty (standard deviation) in the last two digits of the value.

The gas constant occurs in the simplest equation of state, the ideal gas law, as follows:

where:

is the absolute pressure
is absolute temperature
is the volume the gas occupies
is the amount of gas (the number of gas molecules, usually in moles)
is the molar volume

The gas constant has the same units as specific entropy.

Relationship with the Boltzmann constant

The Boltzmann constant kB (often abbreviated k) may be used in place of the gas constant by working in pure particle count, N, rather than number of moles, n, since

,

where is Avogadro's number. For example, the ideal gas law in terms of Boltzmann's constant is .

Specific gas constant

The specific gas constant of a gas or a mixture of gases () is given by the universal gas constant, divided by the molar mass () of the gas/mixture.

It is common to represent the specific gas constant by the symbol . In such cases the context and/or units of should make it clear as to which gas constant is being referred to. For example, the equation for the speed of sound is usually written in terms of the specific gas constant.

The specific gas constant of dry air is

US Standard Atmosphere

The US Standard Atmosphere, 1976 (USSA1976) defines the Universal Gas Constant as:[1][2]

The USSA1976 does recognize, however, that this value is not consistent with the cited values for the Avogadro constant and the Boltzmann constant.[2] This disparity is not a significant departure from accuracy, and USSA1976 uses this value of R for all the calculations of the standard atmosphere. When using the ISO value of R, the calculated pressure increases by only 0.62 pascals at 11,000 meters (the equivalent of a difference of only 0.174 meters – or 6.8 inches) and an increase of 0.292 pascals at 20,000 meters (the equivalent of a difference of only 0.338 meters – or 13.2 inches).

See also

References

  1. "Standard Atmospheres". Retrieved 2007-01-07.
  2. 2.0 2.1 U.S. Standard Atmosphere, 1976, U.S. Government Printing Office, Washington, D.C., 1976 (Linked file is 17 MiB).

External links




Linked-in.jpg