With this specific gas constant calculator, you can determine the specific gas constant of any gas or mixture. You can choose to determine it by specifying the substance's molar mass or by giving its specific heat capacities.

If you'd like to learn more about what the specific gas constant is, its applications, the specific gas constant formula, and how to calculate ir yourself, we invite you to keep reading to find out!

What is the specific gas constant?

The specific gas constant is a physical property associated to a particular gas and is a function of the gas's molar mass. We usually encounter this property in chemistry, fluids, and thermodynamics calculations or studies involving gases or mixtures. We can use it to determine a gas's heat capacity, thermal expansion, and the work done by a gas.

We can determine the specific gas constant RsR_\text s of a particular gas by dividing the universal gas constant RR by its molar mass MM, as shown below:

Rs=R/M\small R_\text s = R/M

If we recall the ideal gas law, we can see how this one is related to the specific gas constant. The ideal gas law is given by:

PV=nRT\small PV = nRT

where:

  • PP – Pressure condition of the gas;
  • VV – Volume occupied by the gas;
  • nn – Number of moles of gas;
  • RR – Universal gas constant; and
  • TT – Temperature condition of the gas.

Here we can substitute the specific gas constant in order to describe the ideal gas law in terms of the specific gas constant as follows:

PV=nRsMT\small PV = nR_\text sMT

Because n×M=mn\times M = m (the mass of gas), we can write the ideal gas law as:

PV=mRsT\small PV = mR_\text sT

The ideal gas law allows us to calculate any of the variables involved, either the gas's volume, pressure, or temperature. You can read and learn more about this equation with our ideal gas law calculator.

How to calculate the specific gas constant

In the last section, we learned that we could calculate the specific gas constant as the ratio between the universal gas constant and the molar mass of the gas or mixture with the following specific gas constant formula:

Rs=R/M\small R_\text s = R/M

where:

  • RsR_\text s – Specific gas constant;
  • RR – Universal gas constant; and
  • MM – Molar mass of the particular gas.

Additionally, we can also find the value of the specific gas constant as the difference between its two specific heat capacities for pressure and volume. This is, by subtracting the specific heat capacity at constant volume from the heat capacity at constant pressure, we can also get the specific gas constant as follows:

Rs=CpCv\small R_\text s = C_\text p - C_\text v

where:

  • CpC_\text p – Specific heat capacity at constant pressure; and
  • CvC_\text v – Specific heat capacity at constant volume.

💡 Use the heat capacity calculator to find the specific heat capacity of any substance!

Specific gas constant of various gases

Below you'll find a table that contains the values of the specific gas constant for the most commonly used gases, including the specific gas constant of air, water, water vapor, and more.

Gas

Molar mass [g/mol]

Specific gas constant [J/kg∙K]

Air

28.9647

287

Argon

39.948

208.13

Butane

58.122

143.05

Carbon dioxide

44.01

188.92

Chlorine

70.90

117.26

Helium

4.00

2077.1

Hydrogen

2.01

4124.2

Methane

16.04

518.28

Nitrogen

28.01

296.8

Oxygen

31.99

259.84

Propane

44.09

188.56

Water vapour

18.01

461.52

How to use this specific gas constant calculator

This specific gas calculator provides two methods for determining the specific gas constant: molar mass and specific heat differences. To make use of this tool:

Molar mass

  1. From the Method field, select the Molar mass method.
  2. In the Molar mass row, input the molar mass of the gas.
  3. The calculator will show the value for the Specific gas constant.

Specific heat

  1. Choose the Specific heat option from the Method row.
  2. Enter the Specific heat capacity at constant pressure (Cp).
  3. Similarly, indicate the value for the Specific heat capacity at constant volume (Cv).
  4. Once you've entered these values, the calculator will display the Specific gas constant.
Gabriela Diaz
Method
Molar mass
Universal gas constant
J⋅K⁻¹⋅mol⁻¹
Molar mass
kg
/mol
Specific gas constant
J/(kg·K)
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